Field

[0001] This disclosure relates to the field of industrial chemical production using photocatalytic reactors, and, in particular, to a cooling system for a photocatalytic reactor.

Background

[0002] Effective, functional photocatalytic reactors are designed such that catalyst contacted with the reactant is illuminated by one or more photon sources in a relatively uniform or predefined gradient intensity, thus driving the chemical reaction. Irradiation of light could be achieved by using natural (e.g., solar) or artificial sources of light (e.g., IR lamps, UV lamps, arc lamps, or light emitting diodes (LEDs)). High-intensity LEDs improve catalysis results, but also generate large amounts of heat that must be removed to avoid damaging LED electronics and/or other components and to optimize the working temperature range for the LEDs.

[0003] Needed is a photoreactor cooling system to maintain LED circuit boards and associated components within an optimized working temperature range.

Summary

[0004] One embodiment set forth herein is directed to a cooling system for a photocatalytic reactor cell that includes a first unitary cooling block and a mounting structure for mounting the first unitary cooling block adjacent to a photocatalyst packed bed such that, in operation, when the first LED circuit board is mounted on the first LED mounting surface, the first plurality of LEDs imparts light to the photocatalyst packed bed. The first unitary cooling block includes a first inlet to receive a first coolant via a first coolant inlet source, a first outlet to discharge the first coolant via a first coolant outlet drain, a first coolant flow passage formed in an interior volume of the first unitary cooling block and coupling the first inlet to the first outlet, and a first LED mounting surface formed on an exterior of the first unitary cooling block for mounting a first LED circuit board proximate to the first coolant flow passage, the first LED circuit board comprising a first plurality of LEDs to be cooled by the photoreactor cooling system.

[0005] The first unitary cooling block is manufactured via a metal additive manufacturing process, such as Direct Metal Layer Melting (DMLM), according to an example embodiment.

[0006] The first cooling block includes a plurality of LED mounting surfaces for mounting a plurality of LED circuit boards, according to an example embodiment. [0007] The cooling system may additionally include a second cooling block similar to the first cooling block and mounted adjacent to the photocatalyst packed bed, according to an example embodiment.

[0008] The photoreactor may be an annular photoreactor or a cylindrical photoreactor, for example. Cooling blocks may be provided on more than one side of a particular photoreactor.

[0009] These, as well as other embodiments, aspects, advantages, and alternatives, will become apparent to those of ordinary skill in the art by reading the following detailed description, with reference where appropriate to the accompanying drawings. Further, this summary and other descriptions and figures provided herein are intended to illustrate embodiments by way of example only and, as such, numerous variations are possible. For instance, structural elements and process steps can be rearranged, combined, distributed, eliminated, or otherwise changed, while remaining within the scope of the embodiments as claimed.

Brief Description of the Drawings

[0010] The accompanying drawings are included to provide a further understanding of the systems, apparatus, devices, and/or methods of the disclosure, and are incorporated in and constitute a part of this specification. The drawings are not necessarily to scale, and sizes of various elements may be distorted for clarity and/or illustrated as simplistic representations to promote comprehension. The drawings illustrate one or more embodiments of the disclosure, and together with the description, serve to explain the principles and operation of the disclosure.

[0011] Figure 1 is an isometric diagram illustrating a first cooling block, according to a first example embodiment.

[0012] Figure 2 is a plan view diagram illustrating the first cooling block, according to the first example embodiment.

[0013] Figure 3 is a plan view diagram illustrating the first cooling block, rotated clockwise approximately 120 degrees from what is illustrated in Figure 2, according to the first example embodiment.

[0014] Figure 4 is a vertical cross-sectional diagram across section 4-4 from Figure 2, illustrating the first cooling block, according to the first example embodiment.

[0015] Figure 5 is a vertical cross-sectional diagram across section 5-5 from Figure 3, illustrating the first cooling block, according to the first example embodiment. [0016] Figure 6 is a vertical cross-sectional diagram illustrating detail 6 from Figure 4.

[0017] Figure 7 is a vertical cross sectional diagram illustrating detail 7 from Figure 5.

[0018] Figure 8 is a vertical cross sectional diagram illustrating detail 8 from Figure 5.

[0019] Figure 9 is a perspective diagram illustrating the first cooling block flipped upside-down from what is illustrated in Figure 1 , according to the first example embodiment.

[0020] Figure 10 is a perspective diagram illustrating a portion of the first cooling block flipped upside-down from what is illustrated in Figure 1, according to the first example embodiment.

[0021] Figure 11 is a perspective diagram illustrating a portion of the first cooling block flipped upside-down from what is illustrated in Figure 1, according to the first example embodiment.

[0022] Figure 12 is an elevational diagram illustrating a first cooling block, according to a second example embodiment.

[0023] Figure 13 is a cross-sectional diagram, taken along section 13-13 in Figure 12, illustrating the first cooling block, according to the second example embodiment.

[0024] Figure 14 is a plan view diagram illustrating the first cooling block, according to the second example embodiment.

[0025] Figure 15 is a vertical cross-sectional diagram across section 15-15 from Figure 14, illustrating the first cooling block, according to the second example embodiment.

[0026] Figure 16 is a plan view diagram, rotated clockwise approximately 110 degrees from what is illustrated in Figure 14, illustrating the first cooling block, according to the second example embodiment.

[0027] Figure 17 is a vertical cross-sectional diagram across section 17-17 from Figure 16, illustrating the first cooling block, according to the second example embodiment.

[0028] Figure 18 is an elevational diagram illustrating a second cooling block, according to an example embodiment.

[0029] Figure 19 is a cross-sectional diagram, taken along section 19-19 in Figure 18, illustrating the second cooling block, according to the example embodiment.

[0030] Figure 20 is an isometric diagram illustrating the second cooling block, according to the example embodiment. [0031] Figure 21 is a vertical cross-sectional diagram, taken along section 21-21 in Figure 20, illustrating the second cooling block, according to the example embodiment.

[0032] Figure 22 is a perspective cutaway diagram illustrating the second cooling block flipped upside-down from what is illustrated in Figures 18-21 , according to the example embodiment.

[0033] Figure 23 is a perspective diagram illustrating the second cooling block illustrated in Figures 18-21 , according to the example embodiment.

[0034] Figure 24 is an elevational diagram illustrating the first cooling block, a first LED circuit board, and couplers, according to an example embodiment.

[0035] Figure 25 is an elevational diagram illustrating the first LED circuit board, according to an example embodiment.

[0036] Figure 26 is an elevational diagram illustrating a cross sectional diagram, taken across section 26-26 of Figure 25, illustrating the first LED circuit board, according to an example embodiment.

[0037] Figure 27 is an elevational diagram illustrating detail 27 of the first LED circuit board of Figure 25, according to an example embodiment.

[0038] Figure 28 is an elevational diagram illustrating detail 28 of the first LED circuit board of Figure 26, according to an example embodiment.

[0039] Figure 29 is an elevational diagram illustrating the first cooling block with a plurality of first LED circuit boards mounted on corresponding first LED mounting surfaces.

[0040] Figure 30 is an isometric diagram illustrating a photocatalytic reactor cell assembly, according to an example embodiment.

[0041] Figure 31 is a vertical cross-sectional diagram illustrating a photocatalytic reactor cell assembly, according to an example embodiment.

[0042] Figure 32 is a horizontal cross-sectional diagram illustrating a photocatalytic reactor cell assembly, according to an example embodiment.

[0043] Figure 33 is a vertical cross-sectional diagram illustrating a photocatalytic reactor cell assembly, according to an example embodiment. [0044] Figure 34 is an isometric diagram illustrating a photocatalytic reactor cell assembly, according to an example embodiment.

[0045] Figure 35 is a vertical cross-sectional diagram illustrating a photocatalytic reactor cell assembly, according to an example embodiment.

[0046] Figure 36 is an isometric diagram illustrating a photocatalytic reactor cell assembly, according to an example embodiment.

[0047] Figure 37 is an elevational diagram illustrating a photocatalytic reactor cell assembly, according to an example embodiment.

[0048] Figure 38 is a perspective diagram illustrating a mounting system for mounting a first cooling block and/or a second cooling block adjacent to a photoreactor cell, according to an example embodiment.

[0049] Figure 39 is a perspective diagram illustrating a mounting system showing the outer cooling block assembly opened, according to an example embodiment.

[0050] Figure 40 is a plot illustrating simulated results and experimental results for the pressure drop of the 3D-printed (i.e., additively manufactured) cooling block at different flowrates.

[0051] Figure 41 is a plot illustrating a surface roughness curve-fit for observed pressure drop data.

[0052] Figure 42 is a plot illustrating resulting heat transfer coefficient and maximum board temperatures for a particular cooling block design.

Detailed Description

[0053] Example systems, apparatus, devices, and/or methods are described herein. It should be understood that the word “example” is used to mean “serving as an example, instance, or illustration.” Any embodiment or feature described herein as being an “example” is not necessarily to be construed as preferred or advantageous over other embodiments or features unless stated as such. Thus, other embodiments can be utilized, and other changes can be made, without departing from the scope of the subject matter presented herein. The aspects described herein are not limited to specific embodiments, apparatus, or configurations, and as such can, of course, vary. It should be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only, and unless specifically defined herein, is not intended to be limiting.

[0054] Throughout this specification, unless the context requires otherwise, the words “comprise” and “include” and variations (e.g., “comprises,” “comprising,” “includes,” “including,” “has,” and “having”) will be understood to imply the inclusion of a stated component, feature, element, or step or group of components, features, elements, or steps, but not the exclusion of any other component, feature, element, or step or group of components, features, elements, or steps.

[0055] Further, unless context suggests otherwise, the features illustrated in each of the figures may be used in combination with one another. Thus, the figures should be generally viewed as component aspects of one or more overall embodiments, with the understanding that not all illustrated features are necessary for each embodiment.

[0056] As used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0057] Ranges can be expressed herein as from “about” one particular value and/or to “about” another particular value. When such a range is expressed, another aspect includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint and independently of the other endpoint.

[0058] Any enumeration of elements, blocks, or steps in this specification or the claims is for purposes of clarity. Thus, such enumeration should not be interpreted to require or imply that these elements, blocks, or steps adhere to a particular arrangement or are carried out in a particular order.

I. Overview

[0059] Described herein is an additively manufactured active cooling system to manage the operating temperature of LED based light modules used in photoreactors that perform chemical reactions. Additive manufacturing allows for a cooling system design having fewer parts, reduced manufacturing time, and, perhaps most importantly, an increased overall heat transfer coefficient (W/(m ² -K)).

[0060] The heat transfer in cooling blocks can be simplified to the overall equation: Q = UA _S &T _LM Equation 1.

Where Q is the total heat transferred between the LEDs and cooling fluid is the surface area in which heat transfer is occurring (m ² ), U is the overall heat transfer coefficient (W/(m2-K)), and AT _LM is the logarithmic mean temperature difference (LMTD) of the system. While LMTD is used in describing the heat transfer in a heat exchanger, it can be applied equally well to the present context. LMTD is defined as: Equation 2.

Where, in the present context: AT ₂ = T _h0 — T _ci Equation 3.

[0061] For a cooling block, T _hi is the maximum temperature of the cooling block, T _h0 is the minimum temperature of the cooling block, T _ci is in the inlet temperature of cooling fluid, and T _co is the outlet temperature of cooling fluid. The overall heat transfer coefficient is the main parameter used to compare the effectiveness of heat exchangers. This provides a measure of the heat transferred between surfaces per degree change in the cooling fluid. The most efficient design theoretically will have the highest heat transfer coefficient with the lowest delta T.

[0062] Additive manufacturing allows a designer to create a part with only the features required to maximize function, thereby minimizing part volume. Traditional manufacturing methods result in increased part volume, complexity, number of assembly steps, and potential for quality issues.

[0063] There are many drawbacks to using a traditional manufacturing method for manufacturing a photoreactor cooling block. Due to the space constraints required by a particular photocatalytic reactor design, low production numbers, and other design details, using traditional manufacturing may result in high cost and time-consuming manufacturing processes to incorporate the needed and/or desired features. The use of custom LED circuit boards means that there is no off-the-shelf cooling solution for many photoreactors. Several manufacturing techniques are implemented when using traditional manufacturing methods, which can result in long lead times. Additive manufacturing allows the consolidation of an entire assembly into a single part, which reduces assembly effort, improves reliability, and reduces leak points.

[0064] The inventors have found that a part that is manufactured with traditional methods generally has a reduced heat transfer performance. The increased volume and smooth cooling surface produced via traditional manufacturing methods results in a lower Heat Transfer Coefficient (HTC). Additive manufacturing (e.g., using DMLM) of a cooling block creates a rough surface finish throughout the cooling channels that provides increased turbulence and effective surface area for heat transfer from the LED circuit boards. COMSOL Multi physics simulations using coupled heat and flow fields to measure the overall heat transfer coefficient (Equation 1) for inner and outer cooling systems for an annular reactor (see Figures 30-37) provide the following results for traditional (e.g., subtractive) manufacturing and additive manufacturing (e.g., DMLM):

Table 1 : Comparison of overall heat transfer coefficients (W/(m ² K))

[0065] The results of these simulations show that the overall heat transfer coefficients are orders of magnitude less for the cooling blocks using subtractive manufacturing when compared to the additively manufactured parts. Therefore, traditionally manufactured cooling blocks would theoretically require a larger temperature difference in the coolant to transfer the same amount of heat from the LED circuit boards, which would, in turn, reduce cooling system efficiency.

II. Example Photoreactor Cooling Systems

A. Example Inner Cooling Block for an Annular Photoreactor (Helical Coolant Passage)

[0066] Figure 1 is an isometric diagram illustrating a first cooling block 300, according to a first example embodiment. Figure 2 is a plan view diagram illustrating the first cooling block 300, according to the first example embodiment. Figure 3 is a plan view diagram illustrating the first cooling block 300, rotated clockwise approximately 120 degrees from what is shown in Figure 2, according to the first example embodiment. Figure 4 is a vertical cross-sectional diagram across section 4-4 from Figure 2, illustrating the first cooling block 300, according to the first example embodiment. Figure 5 is a vertical cross-sectional diagram across section 5- 5 from Figure 3, illustrating the first cooling block 300, according to the first example embodiment. Figure 6 is a vertical cross-sectional diagram illustrating detail 6 from Figure 4. Figures 7 and 8 are vertical cross sectional diagrams illustrating detail from Figure 5. Figures 9-11 are perspective diagrams illustrating the first cooling block 300 flipped upside-down from what is illustrated in Figure 1 , according to the first example embodiment. The following description of the first example embodiment references features and components shown in one or more of Figures 1-11 , where like reference numerals refer to like features and components. As with all figures referenced herein, one or more of Figures 1-11 may omit some features and/or components, as appropriate, to permit better illustration and comprehension.

[0067] As illustrated, the first cooling block 300 is a unitary cooling block, meaning it is formed as a single entity (i.e. , it constitutes a single piece of material in the example embodiment). As described in further detail below, the first cooling block 300 is preferably formed of metal (e.g., aluminum) via an additive manufacturing process. In the example of Figures 1-11 , the first cooling block 300 is generally tube-shaped or cylindrical (with walls having a non-zero thickness), with a generally circular cross section. In other embodiments, the first cooling block 300 may have a shape that is non-cylindrical. For example, the first cooling block 300 may have a square, hexagonal, octagonal, or other regular or non-regular polygonal cross-section. In some embodiments, the cross section may vary in shape and/or diameter/width along a length or height of the first cooling block 300.

[0068] The first cooling block 300 includes at least a first inlet 310, at least a first outlet 320, and at least a first coolant flow passage 330 coupling the first inlet 310 to the first outlet 320. Since the first cooling block 300 is a unitary cooling block, each of the first inlet 310, the first outlet 320, and the first coolant flow passage 330 are also formed in the same unitary structure of the first cooling block 300, and do not constitute separate fabricated parts. Instead, the first inlet 310, the first outlet 320, and the first coolant passage 330 are designed and formed during an additive manufacturing process for fabricating the first cooling block 300 and/or in postmachining of the additively-manufactured first cooling block 300. As illustrated and as described in further detail below, the first cooling block 300 comprises a tube-shaped portion having an inner radius (which may vary along the length of the first cooling block 300, as shown), an outer radius, and a height, where the inner radius and the outer radius define a block thickness sufficiently large to accommodate at least a portion of the first coolant flow passage 330 in an interior volume 302 of the first cooling block 300.

[0069] The first inlet 310 receives a first coolant via a first coolant inlet source (not illustrated but described in further detail below). For example, the first inlet 310 may be a first inlet coupler, such as an internally threaded (female) coupler that interfaces with an externally threaded (male) coupler (e.g., see coupler 312 in Figure 24) of a first coolant inlet hose or tube. Internal threads may be machined into a first inlet cavity (e.g., a post-machined cavity or a cavity designed and formed during an additive manufacturing process) in the first cooling block 300. Alternatively, the first inlet 310 could comprise a first inlet protuberance, such as one that is externally threaded to interface with an internally threaded first coolant inlet tube coupled to the first coolant inlet source. As other examples, in addition to threads, the first inlet 310 may couple to the first coolant inlet source via one or more of the following coupling mechanisms: detents, ridges, grooves, or static friction. In some examples, the coupling mechanism may include at least one spring to provide a spring-loaded force to maintain the coupling between the first inlet 310 and the first coolant inlet source. Other retention mechanisms may also be utilized to maintain the coupling between the first inlet 310 and the first coolant inlet source.

[0070] The first outlet 320 discharges the first coolant via a first coolant outlet drain (not illustrated but described in further detail below). For example, the first outlet 320 may be a first output coupler, such as an internally threaded (female) coupler that interfaces with an externally threaded (male) coupler (e.g., see coupler 314 in Figure 24) of a first coolant outlet hose or tube. Internal threads may be machined into a first outlet cavity (e.g., a post-machined cavity or a cavity designed and formed during an additive manufacturing process) in the first cooling block 300. Alternatively, the first outlet 320 could comprise a first outlet protuberance, such as one that is externally threaded to interface with an internally threaded first coolant outlet tube coupled to the first coolant outlet drain. Similar to the first inlet 310, as other examples, in addition to threads, the first outlet 320 may couple to the first coolant outlet drain via one or more of the following coupling mechanisms: detents, ridges, grooves, or static friction. In some examples, the coupling mechanism may include at least one spring to provide a spring-loaded force to maintain the coupling between the first outlet 320 and the first coolant outlet drain. Other retention mechanisms may also be utilized to maintain the coupling between the first outlet 320 and the first coolant outlet drain.

[0071] In the example shown in Figures 1-11 , the first inlet 310 and the first outlet 320 extend beyond one end of the tube-shaped first cooling block 300 and are closer than the inner radius of the tube-shaped cooling block 300 to a central/vertical axis of the tube-shaped first cooling block 300. This can assist with coupling the first inlet 310 and the first outlet 320 to the respective first coolant inlet source and first coolant outlet drain and can also avoid mechanical interference of the first inlet 310 and the first outlet 320 with LED boards (described in further detail below) mounted on the first cooling block 300.

[0072] The first coolant inlet source supplies the first coolant to the first inlet 310, and may include one or more of a hose or tube, a pump, and/or a chiller, arranged in one or more open or closed loops (e.g., with a heat exchanger). When received at the first inlet 310, the first coolant is chilled (at a lower temperature) than when discharged at the first outlet 320, due to the heat being removed from the cooling block and associated photoreactor as the first coolant flows through the first coolant flow passage 330.

[0073] The first coolant outlet drain receives the first coolant discharged from the first outlet 320, and may include one or more of a hose or tube, pump, chiller, reservoir, and/or cooling fan arranged in one or more open or closed loops (e.g., with a heat exchanger). In some examples, the discharged/heated first coolant is recirculated/recycled in a closed loop cooling system through one or more chillers and pumps to be resupplied to the first inlet 310 and first cooling flow passage 330, after the first coolant has been reduced in temperature from a heated state to a chilled state. In another example, the discharged/heated first coolant is not reused and the first coolant inlet source instead provides fresh/pristine first coolant to the first inlet 310. In some examples, removed heat from the discharged first coolant may be utilized for in-situ power generation.

[0074] The first coolant flow passage 330 is formed in an interior volume 302 (i.e. , as one or more channels) of the first cooling block 300. For the tube-shaped cooling block 300, which has an associated inner radius, outer radius, and height, the interior volume 302 constitutes the circumferential wall thickness (i.e., block thickness) of at least a portion of the tube shape, which generally constitutes the volume between the inner radius and outer radius (rather than the relatively open space closer to the central/vertical axis of the tube). This is illustrated in Figures 2-6, for example. The first coolant passage 330 is designed and formed during an additive manufacturing process for fabricating the first cooling block 300, according to one example. As described in further detail below, manufacturing the first cooling block 300 with the first coolant flow passage 330 via an additive manufacturing technique, such as a Direct Metal Laser Melting (DM LM) process, can provide a number of technical features and resulting benefits. These include an inherent surface roughness in interior wall(s) of the first coolant flow passage 330 resulting from the manufacturing process, which can provide increased turbulence in the first coolant flow. Manufacturing flexibility and customization options are other benefits.

[0075] Turbulent flow of the first coolant through the first coolant flow passage 330 allows for more surface contact between the first coolant and the walls of the first coolant flow passage 330. This, in turn, provides for more efficient heat transfer. Examples set forth herein include technical features to increase turbulence as coolant flows through coolant flow passages in the cooling block. These technical features include the geometry/arrangement of the coolant flow passage through the cooling block, the cross-sectional shape of the coolant flow passage, the surface roughness of the walls of the coolant flow passage, and/or the flow rate of the coolant through the coolant flow passage, among others. Each of these technical features is described in the following paragraphs, with reference to the example of Figures 1-11. Further cooling block features and alterations that may be made to affect heat transfer and other characteristics include taller cooling blocks, shorter cooling blocks, and cooling blocks with differing numbers of LED board mounts.

[0076] The first coolant flow passage 330 may be formed in a number of different patterns in the interior volume 302 of the first cooling block 300. The example shown in Figures 1-11 illustrates the first coolant flow passage 330 arranged in a helical pattern (i.e., a spiral wrapping around the interior volume 302 of the first cooling block 300 from the first inlet 310 upward from near the bottom to near the top of the first cooling block 300. As illustrated in Figure 5, in particular, the top of the helical first coolant flow passage 330 includes a vertical portion leading back toward the bottom of the first cooling block 300 to the first outlet 320. The flow path of the first coolant through the first coolant flow passage winds from bottom to top of the first cooling block 300 in a helical shape, which contributes to enhanced (i.e., more efficient and effective) heat transfer. The helical passage path increases turbulence while minimizing pressure drop compared to other example arrangements. The individual winds or loops of the helically arranged first coolant flow passage 330 are stacked one atop another in close configuration so as to comprise a significant percentage of the interior volume 302 of the first cooling block 300. For example, the first coolant flow passage 330 may comprise up to 20%, or up to 30%, or up to 40%, or up to 50%, or up to 60%, or another significant percentage of the total interior volume of the cooling block 300, so that the first coolant is circulated through an adequate amount of the cooling block 300 for efficient heat removal. While the example of Figures 1-11 includes only a single first coolant flow passage 330, in other examples, the first coolant flow passage 330 could comprise a plurality of subpassages (not shown), perhaps having smaller passage cross-sectional diameters. As an alternative to the first coolant flow passage 330 being arranged in a helical configuration, other arrangements may be utilized, such as a serpentine arrangement, which is shown and described with respect to other examples set forth herein, as well as other arrangements, patterns, and configurations.

[0077] The first coolant flow passage 330 may be formed to have any of a number of different cross-sectional shapes, such as circular, elliptical, oval, ovoid, rounded rhombus, triangular, trapezoidal, polygonal, regular polygonal, or parabolic, for example. In the example illustrated in Figures 1-11 , and in Figure 6 in particular, the first coolant flow passage 330 has a rounded rhombus or double-teardrop cross section. For the helically arranged first coolant flow passage 330, the rounded rhombus design may be particularly beneficial as it avoids using large unsupported overhangs, which better enables the additive manufacturing (e.g., via DMLM) of the first cooling block 300. The rounded rhombus cross section also facilitates better heat transfer (e.g., compared to a circular cross section) as it encourages the flow of the first coolant to be more turbulent. This is partly because additively-manufactured parts having voids with relatively smaller angles (e.g., the top and bottom vertices of the rounded rhombus cross section of the first coolant flow passages 330) tend to have increased surface roughness near the small angles. In contrast, additive manufacturing of voids with relatively larger angles (e.g., 90 degrees or more, such as for a coolant passage having a circular cross section) has a decreased surface roughness.

[0078] As previously mentioned and as described in further detail below, an intentionally introduced surface roughness on the wall(s) of the first coolant flow passage 330 assists in providing a turbulent flow of the first coolant through the first coolant flow passage 330. This, in turn, promotes better heat transfer. The surface roughness can be provided without any post-processing (e.g., surface treatments) after additive manufacturing by selecting and utilizing additive manufacturing technologies that inherently result in parts having a relatively rough finish. While typical additively manufactured parts are often surface-treated or polished to create smooth surface finishes, example embodiments of the cooling block set forth herein intentionally call for using the non-treated raw surfaces resulting from additive manufacturing processes. As a result, the first coolant flow passage 330 has at least one internal wall with a surface roughness sufficient to create turbulence for improved heat transfer as the first coolant flows through the first coolant flow passage 330 from the first inlet 310 to the first outlet 320. In alternative examples, the surface of the wall(s) of the first coolant flow passage 330 can be processed to create a desired roughness, such as by selective etching or other chemical and/or mechanical surface treatment techniques. As an example, to promote a turbulent flow in a coolant flow passage having a cross-sectional diameter of around 1 cm, the wall(s) of the coolant flow passage could have a surface roughness in the range of 3 to 35 micrometers. For example, a surface roughness value of 0.033 mm, which could be expected for a DMLM additive manufacturing process to produce, may be sufficient.

[0079] The particular additive manufacturing process selected will affect surface roughness values of the resulting manufactured part, as will other factors, such as coolant flow passage geometry and feature size. As set forth above, a DMLM process provides a suitable surface roughness value to promote turbulent flow of the first coolant through the first coolant flow passage 330. Other additive manufacturing processes may also be utilized, such as other powder bed fusion processes. This might include Electron Beam Melting (EBM), Selective Laser Sintering (SLS), Selective Heat Sintering (SHS), Direct Metal Laser Sintering (DMLS), or a multi jet fusion process, with or without post-processing surface treatments. In addition to introducing a beneficial surface roughness, additive manufacturing allows the photoreactor cooling system to be easily scaled or modified to fit a wide range of photoreactor sizes and designs. This, in turn, enables quick and efficient manufacture of cooling systems that work with a wide range of different photoreactor or LED board configurations.

[0080] Flow rate of the first coolant through the first coolant flow passage 330 should be controlled (i.e., limited below a certain flow rate based on geometry and other factors) to avoid laminar flow and a resulting reduced heat-transfer capability. For example, pump specifications and/or tube sizes can be chosen to match desired flow rates to assist in achieving turbulent flow, rather than laminar flow.

[0081] The coolant (or cooling fluid) utilized for the first coolant (or any of the other coolants referenced herein) may be selected from the following non-exhaustive list, for example: ammonia, synthetic hydrocarbons of aromatic chemistry (i.e., diethyl benzene [DEB], dibenzyl toluene, diaryl alkyl, partially hydrogenated terphenyl), silicate-esters, aliphatic hydrocarbons of paraffinic and iso-paraffinic type, dimethyl- and methyl phenyl-poly (siloxane), fluorinated compounds such as perfluorocarbons (i.e., FC-72, FC-77) hydrofluoroethers (HFE) and perfluorocarbon ethers (PFE), ethylene glycol, propylene glycol, water, methanol/water, ethanol/water, calcium chloride solution (e.g., 29% by wt.), aqueous solutions of potassium formate and acetate salts, and liquid metals (e.g., Ga-ln-Sn). In general, the coolant is chosen to have a predetermined heat capacity that meets desired cooling requirements.

[0082] In addition to the first inlet 310, the first outlet 320, and the first coolant flow passage

330, the first cooling block 300 additionally includes at least a first LED mounting surface 304 formed on an exterior of the first unitary cooling block 300. For the example illustrated in Figures 1-11 , the first LED mounting surface 304 is one of a plurality (e.g., 21) of rectangular flat (planar) mounting surfaces arranged around the periphery of the first cooling block 300. As such, while appearing to have a circular cross section, the outermost surface of the cooling block 300 may actually have a multi-sided regular polygonal cross section, where each of the flat sides corresponds to an LED mounting surface, such as the LED mounting surface 304. For example, close inspection of Figures 2 and 3 reveals that the cooling block 300 has 21 sides or outer faces/surfaces.

[0083] The first LED mounting surface 304 serves as the interface for mounting a first LED circuit board (not shown in Figures 1-11) onto the first cooling block 300. A plurality of such LED circuit boards are mounted onto a corresponding plurality of LED mounting surfaces formed on an exterior of the first unitary cooling block 300. The description accompanying Figures 24-29, among others, provides additional details regarding example LED circuit boards and LEDs contained on the LED circuit boards. As described in detail below, the LED circuit boards mounted on the first cooling block 300 provide light (via a plurality of LEDs on each LED circuit board) to catalyze chemical reactions in the photoreactor utilizing the first cooling block 300. The first LED mounting surface 304 is formed on an exterior surface of the cooling block 300 proximate (within a small enough distance for efficient heat transfer) the first coolant flow passage 330, which is located in the interior volume 302 of the first cooling block 300. This enables the first LED circuit board and its LEDs, including associated electronics, to be cooled by the photoreactor cooling system comprising the first cooling block 300. In the example of Figures 1-11 and 24-29 (described below), both the exterior surface of the first cooling block 300 and the LED circuit boards have a rigid, flat surface (e.g., a copper base), allowing for flush mounting, which maximizes the effective heat transfer area between the first cooling block 300 and the LED circuit board. In an alternative example, the LED circuit board is a hybrid or flexible circuit board, comprising at least a flexible substrate that can be flushmounted to a curved or non-planar LED mounting surface. One or more thermal management features (e.g., metal heat sinks, thermally conductive dielectrics, and/or heavy copper plane layers) may be incorporated between the LED circuit board and the LED mounting surface on the cooling block, according to some alternative examples. Thermal paste is preferably used to mount (i.e., provide a robust heat transfer interface) the LED circuit board to the LED mounting surface on the cooling block. By minimizing microscopic air gaps and irregularities between the LED circuit board and the LED mounting surface on the cooling block, thermal paste (or another such thermal compound, grease, or material) allows for more efficient and effective heat transfer. [0084] As described in further detail with respect to Figures 24-29, the first cooling block 300 additionally includes one or more mounting holes 380 or other such mechanisms for mounting an LED circuit board onto the first LED mounting surface 304. In the illustrated example, the first cooling block 300 includes two mounting holes 380 on each LED mounting surface, such as the LED mounting surface 304. To avoid interference with the first coolant flow passage 330, the mounting holes are provided below the lowermost winding and above the uppermost winding of the helically wound first coolant flow passage 330. The mounting holes may be formed (i.e., designed and manufactured) as part of the additive manufacturing of the first cooling block 300, for example, with post-machined threads applied to each mounting hole 380. Threaded screws, bolts, and/or other fasteners may then be used to removably secure the LED circuit boards to the mounting surfaces of the cooling block, according to some examples.

[0085] The above description, referencing Figures 1-11 , pertains primarily to a cooling block, of which the first cooling block 300 is an example, and its associated features and functionality for use in a photoreactor cooling system. A photoreactor cooling system utilizing the first cooling block 300 also includes a mounting structure 340 to mount the first cooling block 300 adjacent to a photocatalyst packed bed in the photoreactor, according to at least one example. By mounting the first cooling block 300 adjacent to (e.g., next to or nearby, but not necessarily contacting) the photoreactor’s photocatalyst packed bed, LEDs on the LED circuit boards mounted on the mounting surfaces 304 of the first cooling block 300 impart light to the photocatalyst packed bed during operation, thereby catalyzing one or more chemical reactions.

[0086] To ensure a desired spacing and orientation between the photocatalyst packed bed and the LEDs on the LED circuit boards mounted on the mounting surfaces 304 of the first cooling block 300, the mounting structure 340 is implemented as a centralized mounting structure in the illustrated example. For example, a hub-and-spoke configuration of the illustrated mounting structure allows for a fixed or axially rotatable position relative to a through-rod, such as a threaded through-rod that extends all the way through the vertical axis of the first cooling block 300. Other configurations, besides hub-and-spoke, may alternatively be used, such as those employing struts, cross members, wires, magnets, solid support material, and/or others. The same threaded through-rod may extend through a tube-shaped (annular-shaped) photoreactor cell, so that the photoreactor cell surrounds the first cooling block 300. The threads may interface with either or both of the first cooling block 300 and the tube-shaped photoreactor cell, in example embodiments. This configuration (the overlapping relationship between the photoreactor cell and the cooling block 300) is illustrated in Figures 30-37, for example, as described below. Such a centralized mounting system provides space between the mounted LED circuit boards and the photoreactor for light to freely travel through, optimizing light exposure to the photocatalyst in the photoreactor. Because the first cooling block 300 utilizes a relatively sparse centralized hub-and-spoke mounting structure 340, there remains a significant amount of free space in the interior of the first cooling block 300 (inside the inner radius and near the central axis), which provides room for wiring and/or coolant lines, for example. This, in turn, prevents light blockage that might otherwise occur if the wiring and/or coolant lines interfered with and/or overlapped portions of the LED circuit boards. As best illustrated in Figures 1 , 4, and 5, a wiring/coolant line management system 342 may be employed in the interior of the first cooling block 300 (e.g., around the threaded through-rod) in a triple-helix or other configuration and may utilize ties, binders, loops, or other retention mechanisms.

[0087] In a presently preferred example, the mounting structure 340 (possibly including a wiring/coolant line management system 342) may be part of the same unitary structure as the first cooling block 300, such that the first cooling block 300, including the first inlet 310, first outlet 320, first coolant passage 330, first LED mounting surface 304, and mounting structure 340 (excluding the through-rod) are a single part formed via a metal additive manufacturing process, such as DMLM. In an alternative structure, the mounting structure 340 fastens or otherwise mounts to the first cooling block 300, to allow for mounting the first cooling block 300 adjacent to a photocatalyst packed bed in a photoreactor.

B. Example Inner Cooling Block for an Annular Photoreactor (Serpentine Coolant Passage)

[0088] Figure 12 is an elevational diagram illustrating a first cooling block 400, according to a second example embodiment. Figure 13 is a cross-sectional diagram, taken along section 13- 13 in Figure 12, illustrating the first cooling block 400, according to the second example embodiment. Figure 14 is a plan view diagram illustrating the first cooling block 400, according to the second example embodiment. Figure 15 is a vertical cross-sectional diagram across section 15-15 from Figure 14, illustrating the first cooling block 400, according to the second example embodiment. Figure 16 is a plan view diagram, rotated clockwise approximately 110 degrees from what is illustrated in Figure 14, illustrating the first cooling block 400, according to the second example embodiment. Figure 17 is a vertical cross-sectional diagram across section 17-17 from Figure 16, illustrating the first cooling block 400, according to the second example embodiment. The following description of the second example embodiment references features and components shown in one or more of Figures 12-17, where like reference numerals refer to like features and components. As with all figures referenced herein, one or more of Figures 12-17 may omit some features and/or components in the illustrations or description, as appropriate, to permit better illustration and comprehension. In particular, unless described otherwise, the description accompanying Figures 1-11 for the first embodiment also applies to the second embodiment for similarly named components and is incorporated by reference herein.

[0089] As illustrated, like the first cooling block 300 shown in Figures 1-11 , the first cooling block 400 is a unitary cooling block, meaning it is formed as a single entity (i.e. , it constitutes a single piece of material in the example embodiment) and is preferably formed via a metal additive manufacturing process. In the example of Figures 12-17, the first cooling block 400 is generally tube-shaped or cylindrical (with walls having a non-zero thickness), with a generally circular cross section. In other embodiments, the first cooling block 400 may have a shape that is non-cylindrical. For example, the first cooling block 400 may have a square, hexagonal, octagonal, or other regular or non-regular polygonal cross-section. In some embodiments, the cross section may vary in shape and/or diameter/width along a length or height of the first cooling block 400.

[0090] The first cooling block 400 includes at least a first inlet 410, at least a first outlet 420, and at least a first coolant flow passage 430 coupling the first inlet 410 to the first outlet 420. Since the first cooling block 400 is a unitary cooling block, each of the first inlet 410, the first outlet 420, and the first coolant flow passage 430 are also formed in the same unitary structure of the first cooling block 400, and do not constitute separate fabricated parts. Instead, the first inlet 410, the first outlet 420, and the first coolant passage 430 are designed and formed during an additive manufacturing process for fabricating the first cooling block 400 and/or in postmachining of the additively-manufactured first cooling block 400. As illustrated and as described in further detail below, the first cooling block 400 comprises a tube-shaped portion having an inner radius (which may vary along the length of the first cooling block 300, as shown), an outer radius, and a height, where the inner radius and the outer radius define a block thickness sufficiently large to accommodate at least a portion of the first coolant flow passage 430 in an interior volume 402 of the first cooling block 400.

[0091] The first inlet 410 receives a first coolant via a first coolant inlet source, while the first outlet 420 discharges the first coolant via a first coolant outlet drain. The first coolant flow passage 430 is formed in an interior volume 402 (i.e., as one or more channels) of the first cooling block 400. For the tube-shaped cooling block 400, which has an associated inner radius, outer radius, and height, the interior volume 402 constitutes the circumferential wall thickness (i.e., block thickness) of at least a portion of the tube shape, which generally constitutes the volume between the inner radius and outer radius (rather than the relatively open space near the central/vertical axis of the tube). This is illustrated in Figures 13, 15, and 17, for example.

[0092] As an alternative to the helical pattern in which the first coolant flow passage 330 shown in Figures 1-11 is wound, the first coolant flow passage 430 is instead configured as a serpentine (vertically zig-zagging up and down) arrangement, as best illustrated in Figures 15 and 17. Moreover, while the first coolant flow passage 330 shown in Figures 1-11 had a rounded rhombus cross-sectional shape, the first coolant passage 430 instead utilizes a circular cross section, as best seen in Figure 13.

[0093] The straight (non-curved) nature of the first coolant flow passage 430 and the circular cross section both serve to decrease the amount of turbulence, which worsens the heat transfer characteristics of this design compared to the first example (first coolant flow passage 330) illustrated in Figures 1-11. In addition, the sharp curvature at the top and bottom of each zigzag bend in the serpentine pattern results in an increased undesirable overall pressure drop. Nonetheless, given the surface roughness in the first coolant flow passage 430 imparted by additive manufacturing (e.g., DMLM), the heat transfer coefficient for the first cooling block 400 (the second example embodiment) has been found by the Applicant to be significantly higher (potentially magnitudes higher) than similarly-shaped cooling blocks produced using subtractive manufacturing (i.e., machined metal).

[0094] Similar to the first cooling block 300, the first cooling block 400 additionally includes at least a first LED mounting surface 404 formed on an exterior of the first unitary cooling block 400. For the example illustrated in Figures 12-17, the first LED mounting surface 404 is one of a plurality (e.g., 21) of rectangular flat (planar) mounting surfaces arranged around the periphery of the first cooling block 400. The first LED mounting surface 404 serves as the interface for mounting a first LED circuit board (not shown in Figures 12-17) onto the first cooling block 400. A plurality of such LED circuit boards are mounted onto a corresponding plurality of LED mounting surfaces formed on an exterior of the first unitary cooling block 400. Figures 24-29, among others, and corresponding description provide additional details regarding the LED circuit boards and LEDs contained on the LED circuit boards.

[0095] As described in further detail with respect to Figures 24-29, the first cooling block 400 additionally includes one or more mounting holes 480 or other such mechanisms for mounting an LED circuit board onto the first LED mounting surface 404. In the illustrated example, the first cooling block 400 includes two mounting holes 480 on each LED mounting surface, such as the LED mounting surface 404. To avoid interference with the first coolant flow passage 430, the mounting holes are provided below the lowermost bends and above the uppermost bends of the serpentine-arranged first coolant flow passage 430. The mounting holes may be formed (i.e., designed and manufactured) as part of the additive manufacturing of the first cooling block 400, for example, with post-machined threads applied to each mounting hole 480. Threaded screws, bolts, and/or other fasteners may then be used to removably secure the LED circuit boards to the mounting surfaces of the cooling block, according to some examples.

[0096] The above description, referencing Figures 12-17, pertains primarily to a cooling block, of which the first cooling block 400 is an example, and its associated features and functionality for use in a photoreactor cooling system. A photoreactor cooling system utilizing the first cooling block 400 also includes a mounting structure 440 to mount the first cooling block 400 adjacent to a photocatalyst packed bed in the photoreactor, according to at least one example. By mounting the first cooling block 400 adjacent to (e.g., next to or nearby, but not necessarily contacting) the photoreactor’s photocatalyst packed bed, LEDs on the LED circuit boards mounted on the mounting surfaces 404 of the first cooling block 400 impart light to the photocatalyst packed bed during operation, thereby catalyzing one or more chemical reactions. Similar to as described above with regard to the first example embodiment, a centralized mounting structure, such as a hub-and-spoke configuration and threaded through- rod, may be utilized. Other configurations besides hub-and-spoke may alternatively be used, such as those employing struts, cross members, wires, magnets, solid support material, and/or others. Although not illustrated in Figures 12-17, a wiring/coolant line management system may be employed in the interior of the first cooling block 400 (e.g., around the threaded through-rod) in a triple-helix (similar to the wiring/coolant line management system 342) or other configuration, utilizing ties, binders, loops, or other retention mechanisms.

[0097] In a presently preferred example, the mounting structure 440 (possibly including a wiring/coolant line management system 442) may be part of the same unitary structure as the first cooling block 400, such that the first cooling block 400, including the first inlet 410, first outlet 420, first coolant passage 430, first LED mounting surface 404, and mounting structure 440 (excluding the through-rod) are a single part formed via a metal additive manufacturing process, such as DMLM. In an alternative structure, the mounting structure 440 fastens or otherwise mounts to the first cooling block 400, to allow for mounting the first cooling block 400 adjacent to a photocatalyst packed bed in a photoreactor.

C. Example Outer Cooling Block for an Annular or Cylindrical Photoreactor

[0098] Figures 1-11 and 12-17 set forth two respective example implementations for an inner cooling block for use with an annular photoreactor. The inner cooling block (with LED circuit boards mounted thereon) can be used to provide light emitted toward an inner cell wall of an annular (tube-shaped) photocatalytic reactor cell assembly. In addition to or as an alternative to an inner cooling block, an outer cooling block (with inward-facing LED circuit boards mounted thereon) can be used to provide light toward an outer cell wall of the annular (tubeshaped) photoreactor cell assembly. Figures 30-37 illustrate such an arrangement, and the accompanying description details the construction and operation of the arrangement and underlying photoreactor. The following discussion relates to an outer cooling block (referred to here as a “second cooling block,” where the inner cooling block is referred to as the “first cooling block”) for use with such an annular (tube-shaped) photoreactor assembly. Such an outer cooling block would also work with a cylindrical photoreactor assembly that does not include an inner cooling block.

[0099] In the example embodiments shown and described herein, the outer cooling block comprises two unitary cooling block halves, which may be referred to respectively as a second cooling block and a third cooling block. Manufacturing the outer cooling block as two halves may improve ease of assembly, storage, and/or manufacture, since the outer cooling block will generally be larger (e.g., up to one meter or more in diameter) than the inner cooling block or the photoreactor assembly it surrounds. In an alternative example embodiment, the outer cooling block assembly could instead consist of a full tube-shaped (annular) unitary cooling block rather than two unitary halves (or three unitary thirds or other unitary segmented portions).

[0100] Figure 18 is an elevational diagram illustrating a second cooling block 500, according to an example embodiment. Figure 19 is a cross-sectional diagram, taken along section 19- 19 in Figure 18, illustrating the second cooling block 500, according to the example embodiment. Figure 20 is an isometric diagram illustrating the second cooling block 500, according to the example embodiment. Figure 21 is a vertical cross-sectional diagram, taken along section 21-21 in Figure 20, illustrating the second cooling block 500, according to the example embodiment. Figure 22 is a perspective cutaway diagram illustrating the second cooling block 500 flipped upside down from what is illustrated in Figures 18-21 , according to the example embodiment. Figure 23 is a perspective diagram illustrating the second cooling block 500 illustrated in Figures 18-21 , according to the example embodiment. The following description of the example embodiment of the second cooling block 500 references features and components shown in one or more of Figures 18-23, where like reference numerals refer to like features and components. As with all figures referenced herein, one or more of Figures 18-23 may omit some features and/or components in the illustrations or description, as appropriate, to permit better illustration and comprehension. In particular, unless described otherwise, the description accompanying Figures 1-17 for the first and second example embodiments of the first cooling block also applies to the example embodiment of the second cooling block for similarly named components. Such description is incorporated by reference herein with respect to the second cooling block. In addition, while the components of the second cooling block are referred to as “a first inlet,” “a first outlet,” “a first coolant flow passage,” and so on, where both an inside cooling block and an outside cooling block are included in a photoreactor cooling system, components of the outside cooling block (the second cooling block) may instead be referred to as “a second inlet,” “a second outlet,” “a second coolant flow passage,” etc.

[0101] As illustrated, like the first cooling block 300 shown in Figures 1-17, the second cooling block 500 is a unitary cooling block, meaning it is formed as a single entity (i.e. , it constitutes a single piece of material in the example embodiment) and is preferably formed via a metal additive manufacturing process (e.g., DMLM).The second cooling block 500 is formed as half of a two-part outer cooling block assembly, for ease of installation around the photoreactor assembly. The other half of the two-part outer cooling block assembly (which may be referred to as a third cooling block herein and may be similar to or identical to the second cooling block 500) may then include its own individual components (i.e., inlet, outlet, coolant passage, etc.). In some alternative embodiments, the outer cooling block assembly may comprise more than two cooling blocks, such as would be the case for a three-part or four-part outer cooling block assembly.

[0102] In the example of Figures 18-23, the second cooling block 500 is generally shaped as half of a tube or cylinder (with walls having a non-zero thickness). In other embodiments (e.g., embodiments utilizing a single outer cooling block rather than two halves), the second cooling block 500 may have a shape that is a full tube/cylinder or that is non-cylindrical. For example, the second cooling block 500 may have a square, hexagonal, octagonal, or other regular or non-regular polygonal cross-section or a fraction thereof, such as half of one of these cross- sectional shapes. In some embodiments, the cross section (semicircular in the illustrated example) may vary in shape and/or diameter/width along a length or height of the second cooling block 500.

[0103] The second cooling block 500 includes at least a first inlet 510, at least a first outlet 520, and at least a first coolant flow passage 530 coupling the first inlet 510 to the first outlet 520. Since the second cooling block 500 is a unitary cooling block, each of the first inlet 510, the first outlet 520, and the first coolant flow passage 530 are also formed in the same unitary structure of the second cooling block 500, and do not constitute separate fabricated parts. Instead, the first inlet 510, the first outlet 520, and the first coolant passage 530 are designed and formed during an additive manufacturing process for fabricating the second cooling block 500 and/or in post-machining of the additively-manufactured second cooling block 500. The second cooling block has a thickness sufficiently large to accommodate at least a portion of the first coolant flow passage 530 in an interior volume 502 of the second cooling block 500.

[0104] The first inlet 510 receives a first coolant via a first coolant inlet source, which may be the same as or similar to the first coolant inlet source for the first inlet 310 or 410 of the first cooling block 300 or 400. The first outlet 520 discharges the first coolant (after removing heat from the second cooling block and mounted LED circuit boards) via a first coolant outlet drain, which may be the same as or similar to the first coolant outlet drain for the first outlet 320 or 420 of the first cooling block 300 or 400. As illustrated in Figures 18-23, the first inlet 510 and the first outlet 520 may be situated at a displacement away from the general shape of the second cooling block 500 (e.g., bending slightly outward away from the first coolant flow passages 530) to allow for easier coupling to the respective first coolant inlet source and first coolant outlet drain.

[0105] The first coolant flow passage 530 is formed in an interior volume 502 (i.e. , as one or more channels) of the second cooling block 500. This is illustrated in Figures 19-23, for example. As mentioned, because of space constraints and ease of use, the outer cooling block assembly is preferably split into two halves (of which the cooling block 500 is one half), which makes the use of helical coolant flow passages impractical and not beneficial. The first coolant flow passage 530 is therefore configured as a serpentine (vertically zig-zagging up and down) arrangement in the example embodiment, as best illustrated in Figures 19-23, which accommodates the two-half outer cooling block assembly described above. For a single, tubeshaped outer cooling block, a helical arrangement may instead be used for the first coolant flow passage 530, to allow for better heat transfer characteristics, due to improved turbulence with a relatively lower coolant pressure drop. The first coolant flow passage 530 utilizes a circular cross section, as best seen in Figure 19, 22, and 23; however, other cross-sectional shapes may be used for the first coolant flow passage 530. Manufacturability via a metal additive manufacturing process (e.g., DMLM) is one consideration when selecting which cross-sectional shape to use.

[0106] Similar to as described above with respect to the first cooling blocks 300 and 400, the second cooling block 500 includes an intentionally introduced surface roughness on the wall(s) of the first coolant flow passage 530. This surface roughness assists in providing a turbulent flow of the first coolant through the first coolant flow passage 530, which, in turn, promotes better heat transfer. The surface roughness can be provided without any post-processing (e.g., surface treatments) after additive manufacturing by selecting and utilizing additive manufacturing technologies that inherently result in parts having a relatively rough finish. While typical additively manufactured parts are often surface-treated or polished to create smooth surface finishes, example embodiments of the cooling block set forth herein intentionally call for using the non-treated raw surfaces resulting from additive manufacturing processes. As a result, the first coolant flow passage 530 has at least one internal wall with a surface roughness sufficient to create turbulence for improved heat transfer as the first coolant flows through the first coolant flow passage 530 from the first inlet 510 to the first outlet 520. In alternative examples, the surface of the wall(s) of the first coolant flow passage 530 can be processed to create a desired roughness, such as by selective etching or other chemical and/or mechanical surface treatment techniques. As an example, to promote a turbulent flow in a coolant flow passage having a cross-sectional diameter of around 1 cm, the wall(s) of the coolant flow passage could have a surface roughness in the range of 3 to 35 micrometers. For example, a surface roughness value of 0.033 mm, which is typical for a DMLM additive manufacturing process, may be sufficient.

[0107] Similar to the first cooling block 300, the second cooling block 500 additionally includes at least a first LED mounting surface 504 formed on an exterior surface of the second cooling block 500. However, rather than being on an outwardly facing exterior surface of the cooling block (as is the case for the inner cooling blocks 300 and 400), the first LED mounting surface 504 is formed on an inwardly facing exterior surface of the second cooling block 500, so that an LED circuit board mounted on the first LED mounting surface 504 faces inward toward a photoreactor surrounded (at least in part) by the second cooling block 500. For the example illustrated in Figures 18-23, the first LED mounting surface 504 is one of a plurality (e.g., 20) of rectangular flat (planar) mounting surfaces arranged around the inside exterior surface of the second cooling block 500. The first LED mounting surface 504 serves as the interface for mounting a first LED circuit board (not shown in Figures 18-23) onto the second cooling block 500. A plurality of such LED circuit boards are mounted onto a corresponding plurality of LED mounting surfaces formed on an inward-facing exterior of the second cooling block 500. The first LED mounting surface 504 is formed on an inward-facing exterior surface of the cooling block 500 proximate (within a small enough distance for efficient heat transfer) the first coolant flow passage 530, which is located in the interior volume 502 of the first cooling block 500. This enables the first LED circuit board and its LEDs to be cooled by the photoreactor cooling system comprising the second cooling block 500. The cutaway view in Figure 22 illustrates this proximate relationship between the first LED mounting surface 504 and the first coolant flow passage 530. Figures 24-29, among others, and corresponding description provide additional details regarding the LED circuit boards and LEDs contained on the LED circuit boards. [0108] The second cooling block 500 additionally includes one or more mounting holes 580 or other such mechanisms for mounting an LED circuit board onto the first LED mounting surface 504. In the illustrated example, the second cooling block 500 includes two mounting holes 580 on each LED mounting surface, such as the LED mounting surface 504. To avoid interference with the first coolant flow passage 530, the mounting holes are provided below the lowermost bends and above the uppermost bends of the serpentine-arranged first coolant flow passage 530. The mounting holes may be formed (i.e. , designed and manufactured) as part of the additive manufacturing of the second cooling block 500, for example, with postmachined threads applied to each mounting hole 580. Threaded screws, bolts, and/or other fasteners may then be used to removably secure the LED circuit boards to the mounting surfaces of the cooling block, according to some examples.

[0109] A photoreactor cooling system utilizing the second cooling block 500 also includes a mounting structure 540 (e.g., one or more flanges with through-holes for mounting to one or more brackets) to mount the second cooling block 500 adjacent to a photocatalyst packed bed in the photoreactor, according to at least one example. By mounting the second cooling block 500 adjacent to (e.g., next to or nearby, but not necessarily contacting) the photoreactor’s photocatalyst packed bed, LEDs on the LED circuit boards mounted on the mounting surfaces 504 of the second cooling block 500 impart light to the photocatalyst packed bed during operation, thereby catalyzing one or more chemical reactions. Similar to as described above with regard to the first and second example embodiments of the first cooling block, a centralized mounting structure, such as a hub-and-spoke configuration and threaded through- rod, may be utilized. Other configurations, besides hub-and-spoke, may alternatively be used, such as those employing struts, cross members, wires, magnets, solid support material, and/or others. However, since the second cooling block 500 will generally be much larger than the first cooling block 300 or 400, due to its location relative to the photoreactor cell it surrounds, a different type of mounting system may be preferred.

[0110] In a presently preferred example, instead of a hub-and-spoke and through-rod mounting structure for the second cooling block 500, a system of sliding mounts and rails may be used as or in conjunction with a mounting structure 540 for mounting the second cooling block 500 adjacent to a photocatalyst packed bed in the photoreactor. When appropriately mounted, in operation, when the first LED circuit board is mounted on the first LED mounting surface 504 of the second cooling block 500, the LEDs on the LED circuit board impart light to the photocatalyst packed bed.

[0111] Figures 38 and 39 illustrate an example mounting system 800 that may include both (a) a hub-and-spoke and threaded rod mounting structure 810 for an inner cooling block and photoreactor cell (i.e., similar to as described above for mounting structures 340 and 440) and (b) a sliding mount and rail structure 820 for an outer cooling block (i.e., similar to as described above for the second cooling block mounting structure 540). Figure 38 shows the example mounting system 800 in a closed configuration (outer cooling block assembly opened, such as for maintenance or inspection) while Figure 39 shows the example mounting structure 800 in an open configuration (outer cooling block assembly closed, showing two cooling block halves 500 similar to the second cooling block 500).

[0112] In the illustrated example mounting system 800, a photoreactor cell 100 (e.g., the cell 100 illustrated and described with respect to Figures 30-37) may be mounted in the center of the structure 810 using a threaded rod (802) extending between a first rail mount 812 and a second rail mount 814. The threaded rod may be similar or identical to the tension rod 174 described with respect to Figures 34 and 35, for example, and may also thread onto or otherwise interface with an inner cooling block, such as the cooling block 300 or 400, via a respective mounting structure 340 or 440. Such a configuration may keep the photoreactor cell 100 stationary, but rotatable for alignment or inspection, if desired.

[0113] The outer cooling block assembly (comprised of two halves 500, such as the second cooling block 500) mounts to the sliding mount and rail system 820 at two (or more) points, such as via a first bracket 822 and a second bracket 824, which may interface with the second cooling block at through-holed flanges, such as the mounting structure 540 illustrated in Figures 19, 20, 22, and 23. This allows the outer cooling block assembly to translate in the x- direction as well as rotate about the z-direction, enabling the halves (e.g., the second cooling block 500) to be easily removed for maintenance or moved aside for photoreactor cell removal. The mounting system 800 may be constructed of modular aluminum extrusion pieces, for example, which allows for a similar setup in multiple configurations depending on the enclosure the reactor will be used in. Mounting systems other the example mounting system 800 illustrated in Figures 38 and 39 may alternatively be used, such those providing a more permanent (less adjustable) mounting relationship.

D. Example LED Circuit Boards on LED Mounting Surfaces

[0114] Figure 24 is an elevational diagram illustrating the first cooling block 300, a first LED circuit board 306, and couplers 312/314, according to an example embodiment. Figure 25 is an elevational diagram illustrating the first LED circuit board 306, according to an example embodiment. Figure 26 is an elevational diagram illustrating a cross sectional diagram, taken across section 26-26 of Figure 25, illustrating the first LED circuit board 306, according to an example embodiment. Figure 27 is an elevational diagram illustrating detail 27 of the first LED circuit board 306 of Figure 25, according to an example embodiment. Figure 28 is an elevational diagram illustrating detail 28 of the first LED circuit board 306 of Figure 26, according to an example embodiment. Figure 29 is an elevational diagram illustrating the first cooling block 300 with a plurality of first LED circuit boards mounted on corresponding first LED mounting surfaces. The following description of the example embodiment references features and components shown in one or more of Figures 24-29, where like reference numerals refer to like features and components. As with all figures referenced herein, one or more of Figures 24-29 may omit some features and/or components, as appropriate, to permit better illustration and comprehension. In addition, while Figures 24-29 reference the cooling block 300 and associate components described with respect to Figures 1-11 , the same or similar description would apply to other cooling blocks set forth herein, including the first cooling block 400 and the second cooling block 500.

[0115] In the illustrated example, the first cooling block 300 includes a first mounting surface 304 upon which a first LED circuit board 306 is mounted. The LED circuit board 306 includes a plurality of LEDs 308, including a first LED 308a and a second LED 308b. Thermal paste (or another such thermal compound, grease, or material) is applied between the first mounting surface 304 and the first LED circuit board 306 (which may have a copper base, to further improve thermal conductivity) to minimize microscopic air gaps and irregularities between the first mounting surface 304 and the first LED circuit board 306. Minimizing microscopic air gaps and irregularities between the first mounting surface 304 and the first LED circuit board 306 improves heat transfer characteristics. The first LED mounting surface 304 includes one or more associated mounting holes 380. The first LED circuit board 306 also includes one or more corresponding mounting holes 396 through which a mounting fastener 382, such as a screw, bolt, peg, or other attachment member may be placed and actuated (as appropriate) to mount the first LED circuit board 306 to the first LED mounting surface 304.

[0116] As illustrated, the first LED circuit board 306 may be one of a plurality of identical (or similar) LED circuit boards mounted on corresponding LED mounting surfaces like the first LED mounting surface 304 on the first cooling block 300. In one example embodiment, more than one LED circuit board may be mounted on an individual LED mounting surface. In another example embodiment, a single LED circuit board may span across more than one LED mounting surface, such as if the LED circuit board includes one or more flexible substrate components. As best seen in Figures 24 and 29, the illustrated first LED circuit board 306 is longer than the first LED mounting surface 304, and is even longer than the height of the first cooling block 300. Such an arrangement allows for the plurality of LEDs on each LED circuit board to span the entirety (or nearly the entirety or slightly more than the entirety) of the length of an adjacent photocatalyst packed bed in a photoreactor cell. Electronics associated with the plurality of the LEDs (LED drivers, etc.) can be placed on the ends of LED circuit boards, beyond the extent of the adjacent photocatalyst packed bed, where no light is needed (or desired). One or more light shields can be placed between the plurality of LEDs and LED electronics to confine light to the photocatalyst packed bed (improving efficiency and prolonging LED electronics lifespan). Such light shields may include reflective surfaces, for example, to reflect light back onto the photocatalyst packed bed.

E. Example Cooling System Installed on Annular Photoreactor Cell

[0117] The above discussion provides examples relating to a first cooling block 300/400 and a second cooling block 500 for use with an annular (tube-shaped) photoreactor cell, in which the first cooling block 300/400 and the second cooling board each include a plurality of LED circuit boards 306 mounted on LED mounting surfaces 306/406/506. The following discussion illustrates how the first cooling block 300/400 and second cooling block 500 may be physically incorporated into a photoreactor cell assembly (also referred to as a photocatalytic reactor cell assembly). In addition, a description of the photocatalyst and its placement in the photoreactor cell is also provided.

[0118] The terminology used in the following description of Figures 30-37 differs in some respect from some of the terminology referenced in Figures 1-29, to account for the photoreactor cell being more broadly adaptable to different types of photon emitters besides LEDs, which is one form of photon emitter. For example, the cooling blocks with mounted LEDs are referred to as parts of a “light housing.” In particular, the light housing described below has an outer portion 132a (corresponding to at least one second cooling block 500, for example) and an inner portion 132b (corresponding to a first cooling block 300/400, for example). The following description also sets forth an outer cooling block 134 associated with the outer portion 132a of the light housing and an inner cooling block 138 associated with the inner portion 132b of the light housing. The features and functionality described above with respect to the first cooling block 300/400 and the second cooling block 500 may be beneficially applied to the corresponding respective inner cooling block 138 and outer cooling block 134 set forth below.

[0119] Figure 30 is an isometric diagram illustrating a photocatalytic reactor cell assembly 100, according to a first example embodiment. Figure 31 is a vertical cross-sectional diagram illustrating the photocatalytic reactor cell assembly 100, according to the first example embodiment. Figure 32 is a horizontal cross-sectional diagram illustrating the photocatalytic reactor cell assembly 100, according to the first example embodiment. Figure 33 is a vertical cross-sectional diagram illustrating the photocatalytic reactor cell assembly 100 with installed photocatalyst, according to the first example embodiment. The following description of the first example embodiment references features and components shown in one or more of Figures 30-33, where like reference numerals refer to like features and components. As with all figures referenced herein, one or more of Figures 30-33 may omit some features and/or components, as appropriate, to permit better illustration and comprehension.

[0120] As illustrated, the photocatalytic reactor cell assembly 100 includes an outer cell wall 102 comprising a first tube 104 having a first outer diameter 106 and a first inner diameter 108. The photocatalytic reactor cell assembly 100 also includes an inner cell wall 110 comprising a second tube 112 having a second outer diameter 114 and a second inner diameter 116, where the second outer diameter 114 is smaller than the first inner diameter 108. The outer cell wall 102 and the inner cell wall 110 are arranged concentrically about a vertical axis 118 to define an annular volume 120 between the outer cell wall 102 and the inner cell wall 110.

[0121] In the example of Figures 30-33, the first tube 104 and the second tube 112 are cylindrical, with a circular cross section. In other embodiments, the first tube 104 and/or the second tube 112 may have a shape that is non-cylindrical. For example, one or both of the first tube 104 or the second tube 112 may be constructed of tubing having a square, hexagonal, octagonal, or other regular polygonal cross-section. For embodiments utilizing non-circular cross sections for the first tube 104 and/or the second tube 112, the term “diameter” is intended to refer to a perpendicular distance between the vertical axis 118 and a side (or corner) of the first tube 104 and/or the second tube 112, and the term “annular volume” is intended to refer to the regular-shaped volume between the outer cell wall 102 and the inner cell wall 110. Moreover, the first outer diameter 106 and/or the first inner diameter 108 of the first tube 104 may vary over the height (length) of the first tube 104, such as may be the case if a middle portion of the first tube 104 is wider than end portions. Similarly, the second outer diameter 114 and second inner diameter 116 of the second tube 112 may vary over the height (length) of the second tube 112. For example, the first tube 104 and/or the second tube 112 may have two or more cylindrical portions of differing diameters, with each of the cylindrical portions being joined end-to-end via angular connecting portions that serve as size-adapters between the different cylindrical portions.

[0122] For the embodiment illustrated in Figures 30-33, at least portions of both the outer cell wall 102 and the inner cell wall 110 are constructed of a material that is transparent to photons emitted by photon emitters (described in further detail below), such as LEDs. For example, the outer cell wall 102 and the inner cell wall 110 may be constructed of a material that is transparent to photons in the visible light spectrum. As another example, the outer cell wall 102 and the inner cell wall 110 may be constructed of a material that is transparent to photons in the near-infrared (near-IR) spectrum. As such, the outer cell wall 102 and/or the inner cell wall 110 may be constructed of one or more of the following, without limitation: glass, fused quartz glass, borosilicate glass, or a metallic material. As another alternative, the outer cell wall 102 and/or the inner cell wall 110 may be constructed of a transparent ceramic material, such as one of the materials described in Kachaev, A.A., Grashchenkov, D.V., Lebedeva, Y.E. et al. Optically Transparent Ceramic (Review). Glass Ceram 73, 117-123 (2016). https://doi.org/10.1007/s10717-016-9838-3. In an embodiment utilizing heating only (and not photon emissions) adjacent to either or both of the outer cell wall 102 and/or the inner cell wall 110, the outer cell wall 102 and/or the inner cell wall 110 may comprise coated or polished metal (e.g., stainless steel or aluminum).

[0123] As shown in Figures 31 and 33, the annular volume 120 between the outer cell wall 102 and the inner cell wall 110 may include two or more portions along its height (length), including a middle portion 122 and an upper portion 124. The middle portion may be filled with a photocatalyst packed bed 126, as shown in Figure 33, while the upper portion 124 may serve as a headspace 128 to allow for reactant gas mixing. The upper portion 124 may be empty, as shown in Figure 33, or it may be occupied, at least partially, by a gas mixing material, such as quartz wool, SiC, or beads (e.g., alumina beads and/or silica beads). Additionally, the upper portion 124 may be heated, such as via one or more internal heaters and/or external clamp heaters (not shown).

[0124] The photocatalyst packed bed 126 is positioned in the annular volume 120 between the outer cell wall 102 and the inner cell wall 110. The photocatalyst packed bed 126 has a photocatalyst on a support material. For example, the photocatalyst packed bed 126 may include a photocatalyst co-precipitated with a support material. The photocatalyst may comprise antenna-reactor plasmonic nanoparticles, for example. Various antenna-reactor catalysts developed by Rice University are described in U.S. Patent No. 10,766,024. These antenna-reactor catalysts can effectively utilize light energy to perform various chemical reactions. For example, such antenna-reactor catalysts can be used in the reactor cell embodiments described herein to provide high conversion at high space velocity, resulting in a high hydrogen production rate per unit volume of catalyst bed. Depending on the type of chemical reaction to be performed, an appropriate antenna-reactor catalyst can be matched with correspondingly appropriate LEDs to efficiently activate the photocatalyst, thereby resulting in high reaction rates. For example, in the case of Photocatalytic Steam Methane Reformation (PSMR), a high reaction rate equivalent to 270 micromoles/g/s has been achieved using an appropriate photocatalyst in reactor cell embodiments described herein. [0125] In some embodiments, only a portion of the outer cell wall 102 and/or the inner cell wall 110 is transparent to photons. This transparent portion of the outer cell wall 102 and/or the inner cell wall 110 may correspond to the middle portion 122 of the annular volume 120 illustrated in Figures 31 and 33, such that the transparent portion of the outer cell wall 102 and/or the inner cell wall 110 is directly adjacent to the photocatalyst packed bed 126. For example, in one embodiment, at least a first portion of at least one of the outer cell wall 102 and the inner cell wall 110 is constructed of a material that is transparent to the photons emitted by the photon emitters, while at least a second portion of at least one of the outer cell wall 102 and the inner cell wall 110 includes one or more reflective surfaces to reflect any emitted wayward photons into the photocatalyst packed bed 126. In another example embodiment, at least a first portion of at least one of the outer cell wall 102 and the inner cell wall 110 is constructed of a material that is transparent to the photons emitted by the photon emitters, while at least a second portion of at least one of the outer cell wall 102 and the inner cell wall 110 includes one or more scattering surfaces to scatter any emitted wayward photons into the photocatalyst packed bed 126. The “second portion” referenced in each of the previous two described embodiments may correspond to the upper portion 124 of the annular volume 120 illustrated in Figures 31 and 33, such that the second portion is directly adjacent to the headspace 128, and/or to a portion of the annular volume 120 that is below the photocatalyst packed bed 126 (i.e., on the opposite side of the photocatalyst packed bed 126 from the headspace 128). In yet another example embodiment, both reflective and scattering surfaces may be included in the outer cell wall 102 and/or the inner cell wall 110, or in other components of the photocatalytic reactor cell 100.

[0126] The use of reflective and/or scattering surfaces may help to minimize heat losses from the reactor cell assembly 100. Based on multiphysics simulation modeling using COMSOL, it has been determined that heat losses may be minimized using one or more of the following principles: (a) utilizing appropriate materials at different parts of the reactor to minimize or advantageously re-use the radiative heat transferred from the energized catalyst bed to other parts of the reactor; (b) utilizing appropriate insulation materials at different parts of the reactor; (c) minimizing the use of metal in the reactor and instead using materials with lower thermal conductivity (e.g., glass or quartz), thus increasing the resistance to heat transfer from the photocatalytic reactor cell assembly 100 to the environment. The reactor cell embodiments described herein operate at much lower temperatures then conventional thermal reactors, allowing for the use of materials such as quartz, aluminum, and ceramics. This may reduce the loss of energy from reactor cell assembly 100, thus potentially increasing energy efficiency compared to conventional reactors. [0127] As illustrated in Figure 33, a porous base filter 130 may be included in the annular volume 120 between the outer cell wall 102 and the inner cell wall 110 to position the photocatalyst packed bed 126 in the annular volume 120. When the photocatalytic reactor cell assembly 100 is oriented vertically (perpendicular to the ground) with respect to a gravitational or other force (not shown but assumed to be originating from the bottom of Figure 33), the porous base filter 130 is preferably located at an underside (i.e., bottom) of the photocatalyst packed bed 126. The porous base filter 130 has a plurality of openings (pores) having a pore size chosen to be gas-permeable (to allow resultant gaseous product(s) to flow through) but impermeable to the photocatalyst packed bed 126. For example, the pore size is chosen to be impermeable to the micron-sized aggregates of the photocatalyst nanoparticles and support material (e.g., aerogel) in the photocatalyst packed bed 126. The porous base filter 130 is constructed of a gas-permeable structural material, such as one of the following, without limitation: porous metal, stainless steel (SS316), an austenitic nickel-chromium-based alloy, a nickel-chromium-iron-molybdenum alloy, quartz wool, or ceramic. If both the outer cell wall 102 and the inner cell wall 110 are cylindrical, then the porous base filter 130 preferably has an annular shape corresponding to the shape of the annular volume 120.

[0128] Table 2, below, sets forth example physical dimensions for various example reactor cell embodiments set forth herein:

Table 2.

[0129] The photocatalytic reactor cell 100 illustrated in Figures 30-33 includes a light housing comprising an outer portion 132a (e.g., at least one second cooling block 500) and an inner portion 132b (e.g., a first cooling block 300/400). While both an outer portion 132a and an inner portion 132b of the light housing are illustrated, in some embodiments, either of the outer portion 132a or the inner portion 132b may be omitted from the light housing. The outer portion 132a of the light housing is arranged concentrically around the vertical axis 118 outside the outer cell wall 102. The inner portion 132b of the light housing is arranged concentrically around the vertical axis 118 inside the inner cell wall 110. In the example of Figures 30-33, both the outer portion 132a and the inner portion 132b have a circumferential array of photon emitters (e.g., a plurality of LED circuit boards 306 each having a plurality of LEDs) arranged to emit photons incident on the photocatalyst packed bed 126 in a uniform or other predetermined manner. The circumferential array of photon emitters 142a of the outer portion 132a of the light housing is arranged to emit photons toward the photocatalyst packed bed 126 (i.e., toward an interior of the outer portion 132a). The circumferential array of photon emitters 142b of the inner portion 132b of the light housing is arranged to emit photons toward the photocatalyst packed bed 126 (i.e., generally away from an interior of the inner portion 132b). For example, the circumferential array of photon emitters 142a may be arranged on an inner surface (i.e., inward facing) of the outer portion 132a and the circumferential array of photon emitters 142b may be arranged on an outer surface (i.e., outward facing) of the inner portion 132b, in order to uniformly emit photons incident on the photocatalyst packed bed 126. The emission of photons incident on the photocatalyst packed bed 126 activates continuous photo-induced gas-phase reactions as at least one gaseous reactant flows through the photocatalyst packed bed 126, producing at least one resultant gaseous product.

[0130] In some example embodiments, the outer portion 132a of the light housing is of an outwardly opening clamshell design and comprises two (or more) sections (e.g., two halves each corresponding to the cooling block 500) coupled by a hinge (not shown) or other mounting system (see, e.g., Figure 38 and accompanying description) to allow for installation or removal of the outer portion 132a in the photocatalytic reactor cell assembly 100. Similarly, the inner portion 132b of the light housing may be of an inwardly opening clamshell design comprising two (or more) sections coupled by a hinge (not shown) to allow for installation or removal of the inner portion 132b in the photocatalytic reactor cell assembly 100.

[0131] As illustrated in Figures 30-33, both the outer portion 132a and the inner portion 132b of the light housing are cylindrical, with a circular cross section. In other embodiments, the outer portion 132a and/or the inner portion 132b of the light housing may have a shape that is non-cylindrical. For example, the outer portion 132a and/or the inner portion 132b of the light housing may have a square, hexagonal, octagonal, or other regular polygonal cross-section, such as to match a cross-sectional shape of the first tube 104 and/or the second tube 112. Moreover, the cross-sectional widths of the outer portion 132a and/or the inner portion 132b may vary over the height (length) of the outer portion 132a and/or the inner portion 132b, such as may be the case if a middle portion of the outer portion 132a and/or the inner portion 132b is wider than end portions. For example, the outer portion 132a and/or the inner portion 132b may have two or more cylindrical portions having different diameters, with each of the cylindrical portions being joined end-to-end via angular connecting portions that serve as size- adapters between the different cylindrical portions the outer portion 132a and/or the inner portion 132b of the light housing.

[0132] The exterior of the outer portion 132a of the light housing may be shaped differently than the interior of the outer portion 132a. For example, instead of being cylindrically shaped on both its interior and exterior, the outer portion 132a may be cylindrical on its interior, but surrounded by other equipment, components, and/or materials, such as heat management and/or control equipment, components, and/or materials, giving the exterior a non-cylindrical shape. Similarly, the interior of the inner portion 132b of the light housing may be shaped differently than the exterior of the inner portion 132b. For example, instead of being generally hollow as shown in Figures 30-33, the inner portion 132b may instead be solid or filled with other equipment, components, and/or materials.

[0133] Some or all of the photon emitters in the circumferential array of photon emitters on the outer portion 132a and/or the inner portion 132b may be LEDs mounted on LED circuit boards (e.g., like the LED circuit board 306) or in other configurations, as is illustrated in Figures 30-33 and several other figures herein. For example, the circumferential array of photon emitters on the outer portion 132a and/or the inner portion 132b may include a plurality of LED circuit boards adjacent to one another, mounted on LED mounting surfaces with each LED circuit board comprising a plurality of LEDs. The LEDs may be selected to emit photons in the visible light spectrum (i.e., from about 380 nm to about 750 nm), for example. Other embodiments may include other types of photon emitters, both artificial (e.g., IR bulbs, ultraviolet (UV) lamps and voltaic arc lamps) and natural (e.g., utilizing solar radiation). In general, to promote efficient operation for the photocatalytic reactor cell assembly 100, the photon emitters are selected to emit photons having a sufficient energy and wavelength to activate desired photo-induced gas-phase reactions.

[0134] The photocatalytic reactor cell assembly 100 may also include integrated control electronics to control the photon emitters, as well as drivers to drive the photon emitters. For example, LED drivers may be selected to operate at 50% or greater power load during operation of the photocatalytic reactor cell assembly 100, in order to improve driver efficiency. A system of several or many photocatalytic reactor cell assemblies 100 may share at least some common electronics, for example. In addition to operating the LED drivers at a 50% or greater power load during operation, another design consideration for efficient light delivery is to alter operating current to allow the LEDs to operate at maximum efficiency. In addition, the LEDs themselves may be chosen to have high photon efficiency in the same spectrum range (e.g., same visible spectrum range) as the photocatalyst. Diodes of different semiconductor materials are available with different specified electrical-to-photon energy efficiency. By choosing diodes with high photon efficiency in the same range as the photocatalyst, absorption of light by the catalyst can be increased.

[0135] The outer portion 132a of the light housing may be attached (e.g., via epoxy, adhesive, or mechanical fasteners) to the outer cell wall 102. The inner portion 132b of the light housing may be attached (e.g., via epoxy, adhesive, or mechanical fasteners) to the inner cell wall 110. Alternatively, the outer portion 132a and/or the inner portion 132b of the light housing may simply be positioned adjacent and in close proximity to the outer cell wall 102 and the inner cell wall 110, respectively, without being physically attached. As yet another alternative, a respective separation distance between (a) the outer portion 132a and/or the inner portion 132b of the light housing and (b) the outer cell wall 102 and the inner cell wall 110 may be chosen to realize desired lighting geometries. For example, either or both of the outer portion 132a and the inner portion 132b may have a small separation between itself and the outer cell wall 102 and the inner cell wall 110, respectively. As another example, either the outer portion 132a or the inner portion 132b may have a small separation to the outer cell wall 102 or the inner cell wall 110, while the other has a relatively larger separation. Separation 208 is illustrated as an example separation between the inner cell wall 110 and the inner portion 132b of the light housing. Alternatively or additionally, the outer portion 132a and/or the inner portion 132b of the light housing may include a frame or other structure, such as a unitary cooling block having LED mounting surfaces, upon which the circumferential array of photon emitters is mounted, and which may or may not be attached directly to the outer cell wall 102 and/or the inner cell wall 110. For example, such frame or other structure may be constructed of aluminum, stainless steel (SS316), or some other material. The outer portion 132a and/or the inner portion 132b of the light housing may have a single, unitary frame or structure or may have multiple frames or structures, such as one frame or structure for the outer portion 132a of the light housing and another frame or structure for the inner portion 132b of the light housing. In some embodiments, the mounting frame(s) or structure(s) for the circumferential array(s) of photon emitters may serve as cooling structures, in the form of cooling blocks, cooling jackets, heat sinks, or other heat-dissipation mechanisms.

[0136] The embodiment illustrated in Figures 30-33 includes a cooling structure in the form of an outer cooling block 134 and an inner cooling block 138. The outer cooling block 134 is associated with the outer portion 132a of the light housing, while the inner cooling block 138 is associated with the inner portion 132b of the light housing. As shown, the outer cooling block 134 has a plurality of outer coolant passages 136 (only the coolant inlets/outlets are visible), and the inner cooling block 138 has a plurality of inner coolant passages 140 (only the coolant inlets/outlets are visible). While multiple coolant passages are illustrated in the examples of Figures 30-33, the outer cooling block 134 and/or the inner cooling block 138 may alternatively or additionally include a hollow, walled reservoir through which cooling fluid is circulated throughout its entirety or a portion thereof. For example, the outer cooling block 134 and/or the inner cooling block 138 may comprise walls (e.g., walls made of aluminum, which may be a cost-effective embodiment) defining a receptacle through which the cooling fluid is passed at a predetermined flow rate. In one example embodiment, the outer cooling block 134 and/or the inner cooling block 138 simply acts as a heat sink and does not utilize cooling fluid. In the case of LEDs being used as photon emitters, the cooling structure may maintain a surface on which the photon emitters are mounted at a temperature not exceeding 150 degrees Celsius, for example. In one example embodiment, the outer cooling block 134 includes an inlet, an outlet, a coolant passage coupling the inlet to the outlet, and LED mounting surfaces, as described above with respect to the second cooling block 500. In addition, the inner cooling block 138 may, for example, include an inlet, an outlet, a coolant passage coupling the inlet to the outlet, and LED mounting surfaces, as described above with respect to the first cooling blocks 300 and 400.

[0137] Generally, the outer portion 132a of the light housing may comprise an outer cooling block 134 and the inner portion 132b of the light housing may comprise an inner cooling block 138. The outer cooling block 134 and/or the inner cooling block 138 may be configured to assist in cooling the photon emitters and/or associated electronics, such as LED drivers. For example, the circumferential array of photon emitters may include a plurality of LEDs (on LED circuit boards) mounted on LED mounting surfaces on at least one of the walls (e.g., aluminum walls) of the cooling block(s) 134 and/or 138, so that cooling fluid passing through each cooling block’s coolant passage(s) and/or receptacle(s) assists in cooling the plurality of LED boards. Coolant may be introduced to and removed from the cooling block(s) 134 and/or 138 via one or more coolant lines interfaced with the outer coolant passages 136 and/or the inner coolant passages 140. Such coolant lines (not illustrated) may recirculate/recycle coolant (after appropriate heat removal or dissipation) and/or may introduce new coolant and remove old coolant, with no recirculation.

[0138] Figure 34 is an isometric diagram illustrating the photocatalytic reactor cell assembly 100, according to an example embodiment. Figure 35 is a vertical cross-sectional diagram illustrating the photocatalytic reactor cell assembly, according to an example embodiment. Figures 34 and 35 utilize the same reference numerals as in Figures 30-33 to refer to the same or similar features and/or components. Either or both of Figures 34 and 35 may omit some features and/or components from what is shown in Figures 30-33 (or each other), as appropriate, to permit better illustration and comprehension. For example, Figures 34 and 35 omit at least the outer cooling block 134, inner cooling block 138, details of the outer portion 132a and inner portion 132b of the light housing, photocatalyst packed bed 126, and porous base filter 130. Figures 34 and 35 are presented primarily to illustrate top and bottom endcap fittings of the photocatalytic reactor cell assembly 100, along with various features and components and features associated with the top and bottom endcap fittings. The components and features include mounting structures that may be utilized to mount the photocatalytic reactor cell assembly 100 relative to one or more cooling blocks, as described with respect to Figures 1-23 and 43.

[0139] As shown, the photocatalytic reactor cell assembly 100 includes a top compression endcap fitting 144 having an annular shape. The top compression endcap fitting 144 includes one or more (e.g., four) reactant gas inlets 146 for receiving a continuous flow of input gaseous reactant feedstock, which may include one or more constituent reactant gases. The top compression endcap fitting 144 may have a first outer circumferential flange 148 to fit around a top portion 150 of the outer cell wall 102, a first inner circumferential flange 152 to fit inside or outside a top portion 154 of the inner cell wall 110, or both the first outer circumferential flange 148 and first inner circumferential flange 152. While the above discussion and Figures 34 and 35 illustrate a cylindrical (annular) shape for the top compression endcap fitting 144, a circular shape may alternatively be used. As yet another alternative, non-cylindrical (nonannular) shapes may be suitable for a first tube 104 having a non-circular cross-section. For example, the top compression endcap fitting 144 may have a cross section that matched a regular polygonal cross section of the first tube 104. In addition, either or both of the first outer circumferential flange 148 and the first inner circumferential flange 152 may be omitted, in some embodiments.

[0140] Also as shown, the photocatalytic reactor cell assembly 100 includes a bottom compression endcap fitting 156 having an annular shape. The bottom compression endcap fitting 156 one or more (e.g., four) product gas outlets 158 for outputting a continuous flow of gaseous product, which may include one or more constituent product gases. The bottom compression endcap fitting 156 has a second outer circumferential flange 160 to fit around a bottom portion 162 of the outer cell wall 102, a second inner circumferential flange 164 to fit inside or outside a bottom portion 166 of the inner cell wall 110, or both the second outer circumferential flange 160 and the second inner circumferential flange 164. While the above discussion and Figures 34 and 35 illustrate a cylindrical (annular) shape for the bottom compression endcap fitting 156, a circular shape may alternatively be used. As yet another alternative, non-cylindrical (non-annular) shapes may be suitable for a first tube 104 having a non-circular cross-section. For example, the bottom compression endcap fitting 156 may have a cross section that matched a regular polygonal cross section of the first tube 104. In addition, either or both of the second outer circumferential flange 160 and the second inner circumferential flange 164 may be omitted, in some embodiments.

[0141] The top compression endcap fitting 144 and the bottom compression endcap fitting 156 may be constructed of stainless steel (SS316), an austenitic nickel-chromium-based alloy, a nickel-chromium-iron-molybdenum alloy, or aluminum, for example. The top compression endcap fitting 144 and the bottom compression endcap fitting 156 alternatively or additionally may be constructed of other materials, such as those having a low coefficient of thermal expansion. Moreover, a portion (i.e., an inside-facing portion) of at least one of the top compression endcap fitting 144 and the bottom compression endcap fitting 156 facing the photocatalyst packed bed 126 may be polished to reflect emitted photons into the photocatalyst packed bed 126. Alternatively, a reflective coating (not shown) may be deposited or adhered to the top compression endcap fitting 144 and/or the bottom compression endcap fitting 156 facing the photocatalyst packed bed 126 to accomplish a similar purpose.

[0142] The top compression endcap fitting 144 and the bottom compression endcap fitting 156 respectively form a top seal 168 and a bottom seal 170 with the outer cell wall 102 and the inner cell wall 110. Either or both of the top seal 168 and the bottom seal 170 may be formed via pressure, such as by a compression force applied to a top surface of the top compression endcap fitting 144 and/or a compression force applied to a bottom surface of the bottom compression endcap fitting 156. Such a compression force presses the top and bottom compression endcap fittings 144 and 156 toward each other, vertically sandwiching or squeezing the outer cell wall 102 and the inner cell wall 110 when the photocatalytic reactor cell is oriented vertically (perpendicular to the ground). The top seal 168 and/or the bottom seal 170 may further include one or more gaskets or O-rings, such as an elastomeric gasket and/or O-ring, to create a relatively gas-tight (i.e., gas-impermeable) seal (e.g., a gasket face seal and/or an O-ring seal) between the top compression endcap fitting 144 and/or the bottom compression endcap fitting 156 and the outer cell wall 102 and/or the inner cell wall 110. A combination of gaskets and O-rings may be used to create gas-tight seals, in some embodiments. In some embodiments, the outer cell wall 102 and the inner cell wall 110 may be of different heights (lengths) to accommodate sealing with a gasket as opposed to an O- ring. For example, the inner cell wall 102 may be longer than the outer cell wall 110 to assist in coupling with the top compression endcap fitting 144 and the bottom compression endcap fitting 156. In such a case, it may be beneficial to use a gasket face seal for the inner cell wall 110 and an O-ring seal for the outer cell wall 102. The top seal 168 and/or the bottom seal 170 may include a gasket and/or O-ring located at an end/edge of the outer cell wall 102 or inner cell wall 110 or along a side of the inner cell wall 102 or inner cell wall 110, depending on the configuration of the top compression endcap fitting 144 and/or the bottom compression endcap fitting 156. In other embodiments, no gaskets or O-rings may be necessary, with adequate seals being created through compression force(s). Additionally or alternatively, the top and bottom compression endcap fittings 144 and 156 and/or the first tube 104 and second tube 112 may be constructed of material(s), such as certain plastics, elastomers, or other polymers, that promote a seal when interfaced.

[0143] In the embodiments of Figures 34 and 35, the photocatalytic reactor cell assembly 100 further includes at least one tension rod 174 for imparting a compressive force to the top compression endcap fitting 144 and/or the bottom compression endcap fitting 156. For example, as best illustrated in Figure 35, the tension rod 174 is coupled to both the top compression endcap fitting 144 and the bottom compression endcap fitting 156 to exert a compression force sufficient to cause the top seal 168 and the bottom seal 170 to be formed. The tension rod 174 may also couple with the inner cooling block 138, to mount the inner cooling block 138 adjacent to the photocatalytic reactor cell assembly 100. The tension rod 174 is arranged to be co-linear with the vertical axis 118 about which the outer cell wall 102 and the inner cell wall 110 are concentrically arranged. Where more than one tension rod 174 provides the compression force, a plurality of such tension rods 174 may each be spaced a common distance from and around the vertical axis 118 relative to one another, to apply the compression force relatively evenly around the circumference or perimeter of the top compression endcap fitting 144 and/or the bottom compression endcap fitting 156. The tension rod(s) 174 may be located inside and/or outside the outer cell wall 102, the inner cell wall 110, and/or the light housing (e.g., with cooling block). The tension rod(s) 174 may be constructed of stainless steel (SS316), an austenitic nickel-chromium-based alloy, a nickel-chromium-iron- molybdenum alloy, or aluminum, for example. The tension rod(s) 174 alternatively or additionally may be constructed of another material. In a further embodiment, the tension rod(s) 174 may serve as a mounting structure for mounting the photocatalytic reactor cell 100 to another structure, such as a multi-cell system of sliding mounts and rails that forms part of a larger reactor system. In some embodiments, the inner portion 132b and/or the outer portion 132a (and/or associated inner and/or outer cooling blocks 138/134) of the light housing fastens to the tension rod(s) 174.

[0144] The tension rod(s) 174 may include threads cooperating with at least one threaded fastener 176 to facilitate tightening of the top compression endcap fitting 144 and/or the bottom compression endcap fitting 156 onto the outer cell wall 102 and the inner cell wall 110. The top compression endcap fitting 144 and/or the bottom compression endcap fitting 156 may each include a support 172 through which the tension rod 174 exerts the compression force. The support(s) 172 may be threaded or non-threaded to interact with the tension rod(s) 174 and/or with threaded fastener(s) 176. As an alternative to threads, springs, clamps, air pressure, and/or other mechanisms may be used to apply the compression force. The support(s) 172 may be constructed of stainless steel (SS316), an austenitic nickel-chromium- based alloy, a nickel-chromium-iron-molybdenum alloy, or aluminum, for example. The support(s) 172 alternatively or additionally may be constructed of another material. In the example embodiments shown in Figures 34 and 35, the support 172 generally has a conical shape, with the top compression endcap fitting 144 and the bottom compression endcap fitting 156 serving as a respective base for each of the conical supports 172 and the tension rod tightening on to the respective apex of each of the conical supports 172. Alternatively, the support(s) 172 may have other shapes. In yet other embodiments, the tension rod 172 physically interfaces directly with the top compression endcap fitting 144 and/or the bottom compression endcap fitting 156, as may be the case for a top compression endcap fitting 144 and/or bottom compression endcap fitting 156 having a disk shape (instead of an annulus shape) or other shape without a center void. As mentioned, a plurality of tension rods 174 may be coupled to each of the top compression endcap fitting 144 and the bottom compression endcap fitting 156 to exert a collective compression force sufficient to cause the top seal and the bottom seal to be formed. Potential advantages imparted by the use of one or more tension rods 174 include: (a) little to no interference with photons, thus improving overall efficiency of the photoreactor, (b) less exposure to high temperatures compared to other sealing mechanisms, thereby limiting thermal expansion, (c) improved force distribution on the sealing surfaces compared to a multi-bolt flange system, and (d) concentrated compression force between the concentric quartz tubes to limit deformation of the compression end caps without the use of hardware that penetrates the catalyst bed, which accordingly limits potential energy losses from the catalyst to the hardware that would otherwise penetrate the catalyst bed, among others.

[0145] Referring back to Figure 33, when the photocatalytic reactor cell assembly 100 is oriented vertically (perpendicular to the ground) with respect to a gravitational force (not shown, but assumed to originate from the bottom of Figure 33), the porous base filter 130 is preferably located at an underside (i.e. , bottom) of the photocatalyst packed bed 126 closer to the bottom compression endcap fitting 156 than to the top compression endcap fitting 144. The photocatalyst packed bed 126 is positioned vertically in a middle portion 122 of the annular volume 120. The upper portion 124 of the annular volume 120 closest to the top compression endcap fitting 144 is devoid of the photocatalyst packed bed 126 to provide the sufficient headspace 128 for reactant gas mixing. The emission (by the plurality of photon emitters 142a and 142b) of photons incident on the photocatalyst packed bed 126 activates continuous photo-induced gas-phase reactions as at least one gaseous reactant introduced via the gas inlet 146 flows through the photocatalyst packed bed 126 and at least one resultant product gas exits via the gas outlet 158.

[0146] Figure 36 is an isometric diagram and Figure 37 is an elevational diagram illustrating the photocatalytic reactor cell assembly 100, according to another example embodiment. Figures 36 and 37 utilize the same reference numerals as in Figures 30-35 to refer to the same or similar features and/or components. Either or both of Figures 36 and 37 may omit some features and/or components from what is shown in Figures 30-35 (or each other), as appropriate, to permit better illustration and comprehension. For example, Figures 36 and 37 omit (but the described example embodiment may include) at least the outer cooling block 134, inner cooling block 138, details of the outer portion 132a and inner portion 132b of the light housing, photocatalyst packed bed 126, and porous base filter 130. Figures 36 and 37 are presented primarily to illustrate a variation (i.e. , without supports 172 and tension rod 174) of the top and bottom endcap fittings 144 and 156 of the photocatalytic reactor cell assembly 100 shown in Figures 34 and 35. As such, the photocatalytic reactor cell assembly 100 of Figures 36 and 37 is of simpler construction than the photocatalytic reactor cell assembly 100 of Figures 34 and 35.

[0147] As shown in Figures 36 and 37, the photocatalytic reactor cell assembly 100 includes an outer cell wall 102 and an inner cell wall 110 on which a top compression endcap fitting 144 and a bottom compression endcap fitting 156 are mounted on respective top and bottom portions of the outer cell wall 102 and the inner cell wall 110. The top compression endcap fitting 144 includes a reactant gas inlet 146, a first outer circumferential flange 148 to fit around the top portion 150 of the outer cell wall 102, and a first inner circumferential flange 152 to fit inside the top portion of the inner cell wall 110. Similarly, the bottom compression endcap fitting 156 includes a product gas outlet 158, a second outer circumferential flange 160 to fit around the bottom portion 162 of the outer cell wall 102, and a second inner circumferential flange (not illustrated) to fit inside the bottom portion of the inner cell wall 110. In some example embodiments, the top compression endcap fitting 144 and the bottom compression endcap fitting 156 are press-fit onto the outer cell wall 102 and an inner cell wall 110. Alternatively, the top compression endcap fitting 144 and the bottom compression endcap fitting 156 are press- fit onto a light housing surrounding at least a portion (e.g., the outside and the inside, respectively) of the outer cell wall 102 and an inner cell wall 110. Other attachment configurations and/or mechanisms may also be used. F. Design Considerations for Additively Manufactured Cooling Blocks

[0148] The inventors have found that fluid flow and heat transfer are the most important features of the cooling passages for the cooling blocks set forth herein. Determining an optimal geometry of the cooling passages involves the use of the Navier-Stokes equations to solve for the velocity and pressure fields. The equations are a result of differential momentum and mass balances:

V(p • u) = 0 Equation 4. p(u ■ V)u = V • [— p + T] + F Equation 5.

Where: p - Density of fluid (kg/m ³ ) u - Velocity of fluid (m/s) p - Pressure of fluid (Pa)

T - Viscous stress tensor (Pa)

F - Volume force (N/m ³ )

[0149] From an energy balance, considering conduction and convection, the fowllowing heat transfer equation results: pCpU • VT + V • q = Q Equation 6. q = —kVT Equation 7.

Where:

C _p - Heat capacity of material (J/(kg*K))

T - Temperature field (K) k - Thermal conductivity of material (W/m ² )

Q - General heat source (W/m ³ )

[0150] To determine the effectiveness of a particular cooling block design, Equations 4-7 need to be solved. Since the properties are temperature dependent, these four equations need to be solved simultaneously using the finite element method. This is done using COMSOL Multi physics simulation software, for example, where the geometry and physics can be set up. With the inlet temperature of cooling fluid (coolant), flowrate of the fluid, and energy deposited on the LED board surface, Equations 4-7 can be solved. The overall heat transfer coefficient can be used to evaluate the particular cooling block: Equation 8.

Where: q - The heat deposited on the boards (W)

- Surface area of heat transfer (m ² )

AT _LM - Delta log mean temperature difference [0151] To validate the fluid flow part of the model, the pressure drop of the cooling block at different flowrates was measured. Equations 4 and 5 were solved given the inlet flowrates. Figure 40 is a plot 900 illustrating simulated results and experimental results for the pressure drop of the 3D-printed (i.e., additively manufactured) cooling block at different flowrates.

[0152] The discrepancies between the simulated and experimental pressure drop can be explained by the surface roughness on the interior walls of the coolant flow passage. The simulation assumes a smooth surface, so the turbulence that is caused by the surface roughness of the additively manufactured material is not accounted for. A friction factor is applied through a volume force to account for the roughness: Equation 9.

Where: f _D - Is the friction factor

D _H - Is the hydraulic diameter

[0153] For a circular flow cross section, the hydraulic diameter is just the diameter of the circle comprising the cross section, but in general, it can be expressed as four times the cross sectional area divided by the perimeter. The friction factor can be found from any of many experimental correlations (the Churchill equations were used in this case) and is a function of the surface roughness.

[0154] A surface roughness of 0.033 mm fits the pressure drop data the best, as illustrated in the plot 902 shown in Figure 41. A full heat transfer model utilizing this determined surface roughness was then simulated with various inlet coolant flowrates and 2200 W of energy deposited onto the LED circuit boards mounted on the cooling block.

[0155] The resulting heat transfer coefficient and maximum board temperatures are illustrated in the plot 904 of Figure 42. The results show a relatively good heat transfer between the LED circuit boards and the coolant.

[0156] In conducting simulations and experiments, the inventors have identified a number of manufacturing considerations for cooling passage geometry. For inner cooling blocks (e.g., the cooling blocks 300 and 400), the use of helical passages allows for the elimination of sharp 180-degree turns, which results in lower pressure drop. The rounded rhombus (i.e., diamond) shape enables additive manufacturing of helical passages with minimal deformation that might otherwise result from unsupported surfaces. For outer cooling blocks (e.g., the cooling block 500) that make up half of an outer cooling block assembly, the passages only cover 180 degrees. Since a helical arrangement is impractical for passages that only cover 180 degrees, the manufacturing process will yield poor results with long, horizontal passages. In the vertical orientation a cooling passage with a smaller diameter can be used to facilitate manufacturing. The pressure drop is much higher in this style of cooling block.

[0157] In various embodiments, the current invention includes a photoreactor cooling system. For example, in one embodiment, the photoreactor cooling system includes a first unitary cooling block having a first inlet to receive a first coolant via a first coolant inlet source, a first outlet to discharge the first coolant via a first coolant outlet drain and a first coolant flow passage formed in an interior volume of the first unitary cooling block and coupling the first inlet to the first outlet, and a first LED mounting surface formed on an exterior of the first unitary cooling block for mounting a first LED circuit board proximate to the first coolant flow passage, the first LED circuit board comprising a first plurality of LEDs to be cooled by the photoreactor cooling system. The photoreactor system of the current example further includes a mounting structure for mounting the first unitary cooling block adjacent to a photocatalyst packed bed such that, in operation, when the first LEDS circuit board is mounted on the first LED mounting surface, the first plurality of LEDs imparts light to the photocatalyst packed bed. The coupling mechanism included in the photoreactor cooling system may be spring loaded in accordance with one or more embodiments.

[0158] In some example embodiments, the first coolant flow passage has at least one internal wall with a surface roughness sufficient to create turbulence for improved heat transfer as the first coolant flows through the first coolant flow passage from the first inlet to the first outlet. The surface roughness in the at least one internal wall of the first coolant flow passage may be formed via a chemical surface treatment or by a mechanical surface treatment. In some example embodiments, the chemical surface treatment may be a post-processing selective etching treatment.

[0159] In some example embodiments, the first unitary cooling block is formed using an additive manufacturing process that inherently results in the surface roughness in the at least one internal wall of the first coolant from passage. In some example embodiments, the additive manufacturing process includes a powder bed fusion process, while in other example embodiments, the additive manufacturing process may also include a Direct Metal Laser Melting (DMLM) process, an Electron Beam Melting (EBM) process, a Selective Laser Sintering (SLS) process, a Selective Heat Sintering (SHS) process, a Direct Metal Laser Sintering (DMLS) process, or a multi jet fusion process. The first unitary cooling black in some example embodiments includes a tube-shaped portion having an inner radius, an outer radius, and a height. The inner and outer radius of this example embodiment define a block thickness sufficiently large to accommodate at least a portion of the first coolant flow passage in the interior volume of the first unitary cooling block.

[0160] In some example embodiments, the first inlet and the first outlet of the photoreactor cooling system extends beyond one end of the tube-shaped portion and are closer than the inner radius to a central axis of the tube-shaped portion. The first inlet in some example embodiments may include a first inlet coupler and the first outlet includes a first outlet coupler. In some example embodiments, the first inlet includes a first inlet cavity, and the first inlet cavity may be internally threaded to interface with an externally threaded first coolant inlet tube coupled to the first coolant inlet source. In some example embodiments, the first outlet includes a first outlet cavity and the first outlet cavity may be internally threaded to interface with an externally threaded first coolant outlet tube coupled to the first coolant outlet drain. The first inlet cavity and the first outlet cavity may each include internal threads machined in the first unitary cooling block. In some example embodiments, the first inlet may include a first inlet protuberance and the first outlet may include a first outlet protuberance. The first inlet protuberance may be externally threaded to interface with an internally threaded first coolant inlet tube coupled to the first coolant inlet source and the first outlet protuberance may be externally threaded to interface with an internally threaded first coolant outlet tube coupled to the first coolant outlet drain. In some example embodiments, the first inlet and the first outlet may respectively couple with the first coolant inlet source and the first coolant outlet drain via a coupling mechanism including threads, detents, friction, ridges, or grooves.

[0161] In some example embodiments, the photocatalyst packed bed included in the photoreactor cooling system may be contained in a tube-shaped portion of a photoreactor cell that concentrically surrounds the tube-shaped portion of the first unitary cooling block. In one example embodiment, the photocatalyst packed bed may be contained in a tube-shaped portion of a photoreactor cell that is concentrically surrounded by the tube-shaped portion of the first unitary cooling block. In other example embodiments, the photocatalyst packed bed may be contained in a cylindrical portion of a photoreactor cell that is centrically surrounded by the tube-shaped portion of the first unitary cooling block. The first unitary cooling block may comprise a metal or metal alloy in some example embodiments, in other example embodiments, the first unitary cooling block may comprise aluminum.

[0162] In some example embodiments, the first coolant flow passage is arranged in a serpentine pattern in the interior volume of the first unitary cooling block between the first inlet and the first outlet. In other example embodiments, the first coolant flow passage is arranged in a helical pattern in the interior volume of the first unitary cooling block between the first inlet and the first outlet. In some example embodiments, the first coolant flow passage includes a plurality of subpassages. In some example embodiments, the first coolant flow passage has a cross section shape that may include being elliptical, oval, ovoid, rounded rhombus, triangular, trapezoidal, polygonal, regular polygonal, parabolic, double-teardrop, or circular. While some example embodiments have described various cross section shapes from the first coolant flow passage, it should be understood that the cross section shape may also be any shape, including those not explicitly stated without deviating from the scope of this disclosure.

[0163] In various example embodiments, the photoreactor cooling system includes a first LED mounting surface. In one example embodiment, the first LED mounting surface includes a planar surface. In other example embodiments, the first LED mounting surface is one of a plurality of LED mounting surfaces for moutnign a respective plurality of LED circuit boards each having a plurality of LEDs.

[0164] In various example embodiments, the photoreactor cooling system includes a first unitary cooling block. In some example embodiments, the first unitary cooling block is tubeshaped and the plurality of LED mounting surfaces includes a plurality of adjacently aligned planar surfaces spanning an exterior circumference of first unitary cooling block. In another example embodiment, the first unitary cooling block is cylinder-shaped and the plurality of LED mounting surfaces may include a plurality of adjacently aligned planar surfaces spanning an exterior circumference of the first unitary cooling block. In another example embodiment, the first unitary cooling block may be tube-shaped, and the plurality of LED mounting surfaces may include a plurality of adjacently aligned planar surfaces spanning an interior circumference of the first unitary cooling block.

[0165] In various embodiments, the photoreactor cooling system may include a second unitary cooling block having a second inlet to receive a second coolant via a second coolant inlet source, a second outlet to discharge the second coolant via a second coolant outlet drain, a second coolant flow passage formed in an interior volume of the second unitary cooling block and coupling the second inlet to the second outlet, and a second LED mounting surface formed on an exterior of the second unitary cooling block for mounting a second LED circuit board proximate to the second coolant flow passage, where the second LED circuit board may include a second plurality of LEDs to be cooled by the photoreactor cooling system. In some example embodiments, the mounting structure for mounting the first unitary cooling block adjacent to the photocatalyst packed bed may also mount the second unitary cooling block adjacent to the photocatalyst packed bed such that, in operation, when the second LED circuit board is mounted on the second LED mounting surface, the second plurality of LEDs may impart light to the photocatalyst packed bed. The some example embodiments, the second coolant inlet source may be coupled to the first coolant inlet source and the second coolant outlet drain may be coupled to the first coolant outlet drain.

[0166] In various embodiments, the photoreactor cooling system may also include a third unitary cooling block. The third unitary cooling block may include a third inlet to receive a third coolant via a third coolant inlet source, a third outlet to discharge the third coolant via a third coolant outlet drain, a third coolant flow passage formed in an interior volume of the third unitary cooling block and coupling the third inlet to the third outlet, and a third LED mounting surface formed on an exterior of the third unitary cooling block for mounting a third LED circuit board proximate to the third coolant flow passage, where the third LED circuit board may have a third plurality of LEDs to be cooled by the photoreactor cooling system. In some example embodiments, the mounting structure for mounting the first and second unitary cooling blocks adjacent to the photocatalyst packed bed also mounts the third unitary cooling block adjacent to the photocatalyst packed bed such that, in operation, when the third LED circuit board is mounted on the third LED mounting surface, the third plurality of LEDs may impart light to the photocatalyst packed bed.

[0167] In some example embodiments, the first, second, and third coolant inlet sources may be coupled to one another, and the first, second, and third coolant outlet drains may be coupled to one another. In some example embodiments, the photocatalyst packed bed may be positioned in an annular photoreactor cell, where the first unitary cooling block is an inner cooling block, where the second unitary cooling block is a first half of an outer cooling block assembly, and where the third unitary cooling block is a second half of the outer cooling block assembly. In some example embodiments, the photoreactor cooling system may also include a pump and a chiller for coolant re-circulation.

[0168] In various embodiments, the current invention also discloses a method for manufacturing a cooling block for a photoreactor. In some embodiments, this method may include forming via an additive manufacturing process, a unitary cooling block having a first inlet, a first outlet, and a first coolant flow passage coupling the first inlet to the first outlet. In some embodiments, the first coolant flow passage may be formed in an interior volume of the unitary cooling block. In some example embodiments, the additive manufacturing process is selected to impart a predetermined surface roughness to at least one internal wall of the first coolant flow passage.

[0169] In some example embodiments, the method may further include forming, via the additive manufacturing process, a plurality of LED mounting surfaces on an exterior of the unitary cooling block, where the plurality of LED mounting surfaces for mounting a plurality of LED circuit boards each include a plurality of LEDs. In some example embodiments, the method may further include forming a plurality of mounting holes in the unitary cooling block for mounting the plurality of LED circuit boards to the plurality of LED mounting surfaces on the exterior of the unitary cooling block, where each of the plurality of LED circuit boards includes at least one respective mounting hole through which a respective mounting fastener can mount that LED circuit board to a respective one of the plurality of LED mounting surfaces. In some example embodiments, the plurality of mounting holes may be formed in the unitary cooling block via the additive manufacturing process, and the method may further include providing mounting threads in each of the plurality of mounting holes in the unitary cooling block via post-processing, where the threads in each of the plurality of mounting holes for cooperatively engaging with corresponding threads on each of a plurality of externally threaded mounting fasteners to mount the plurality of LED circuit boards to the plurality of LED mounting surfaces.

[0170] In some example embodiments, the method may further include applying a thermally conductive substance between each of the plurality of LED circuit boards and each of the plurality of LED mounting surfaces when mounting the plurality of LED circuit boards on the plurality of LED mounting surfaces. In some embodiments, the thermally conductive substance includes thermal paste. In some example embodiments, the method may further include forming, via the additive manufacturing process, a mounting structure for mounting the unitary cooling block adjacent to a photocatalyst packed bed in a photocatalytic reactor cell assembly. In some example embodiments, the method may further include providing a mounting structure for mounting the unitary cooling block adjacent to a photocatalyst packed bed so that the plurality of LEDs impart light onto the photocatalyst packed bed to catalyze at least one chemical reaction. In some example embodiments, the method may further include forming, via the additive manufacturing process, a wiring/coolant line management system for positioning at least one of wiring or a coolant line proximate a central vertical axis of the unitary cooling block. In some embodiments, the wiring/coolant line management system may be formed as a double-helix or triple-helix structure and may also include at least one retention mechanism selected from the group consisting of ties, binders, or loops.

[0171] In various embodiments, the current invention also discloses a photocatalytic cell assembly. In some example embodiments, the photocatalytic reactor cell may include an outer cell wall comprising a first tube having a first outer diameter and a first inner diameter, an inner cell wall with a second tube having a second outer diameter and a second inner diameter, where the second outer diameter is smaller than the first inner diameter, and where the outer cell wall and the inner cell wall are arranged concentrically about a vertical axis to define an annular volume between the outer cell wall and the inner cell wall. The photocatalytic cell in some example embodiments may also include a top compression endcap fitting having an annular shape and comprising a reactant gas inlet, a bottom compression endcap fitting having an annular shape and including a product gas outlet, where the top compression endcap fitting and the bottom compression endcap fittings respectively form a top seal and a bottom seal with the outer cell wall and the inner cell wall, a photocatalyst packed bed positioned in the annular volume between the outer cell wall and the inner cell wall, where the photocatalyst packed bed comprises a photocatalyst, and a light housing comprising an inner cooling block and an outer cooling block.

[0172] The inner cooling block in some embodiments, may be arranged concentrically around the vertical axis inside the inner cell wall and may include a first inlet to receive a first coolant via a first coolant inlet source, a first outlet to discharge the first coolant via a first coolant outlet drain, a first coolant flow passage formed in an interior volume of the inner cooling block and coupling the first inlet to the first outlet, and a first LED mounting surface formed on an exterior of the inner cooling block for mounting a first LED circuit board proximate to the first coolant flow passage, the first LED circuit board having a first plurality of LEDs to be cooled by the first coolant flowing through the first coolant flow passage. The outer cooling block may be arranged concentrically around the vertical axis outside the outer cell wall in some embodiments, and may also include a second inlet to receive a second coolant via a second coolant inlet source, a second outlet to discharge the second coolant via a second coolant outlet drain, a second coolant flow passage formed in an interior volume of the outer cooling block and coupling the second inlet to the second outlet, and a second LED mounting surface formed on an exterior of the outer cooling block for mounting a second LED circuit board proximate to the second coolant flow passage, the second LED circuit board may include a second plurality of LEDs to be cooled by the second coolant flowing through the second coolant flow passage. The first and second pluralities of LEDs may emit photons incident on the photocatalyst packed bed to activate continuous photo-induced gas-phase reactions as at least one gaseous reactant introduced via the reactant gas inlet flows through the photocatalyst packed bed and at least one resultant gaseous product exits via the product gas outlet.

[0173] In some example embodiments of the photocatalytic reactor cell assembly, the first coolant flow passage and the second coolant flow passage each may have at least one internal wall with a surface roughness sufficient to create turbulence for improved heat transfer as the first and second coolants flow through the first and second coolant flow passages. In some example embodiments of the photocatalytic reactor cell assembly, the inner and outer cooling blocks may be formed using an additive manufacturing process that inherently results in the surface roughness. In some example embodiments of the photocatalytic reactor cell, the additive manufacturing process may include a powder bed fusion process, a Direct Metal Laser Melting (DMLM) process, an Electron Beam Melting (EBM) process, a Selective Laser Sintering (SLS) process, a Selective Heat Sintering (SHS) process, a Direct Metal Laser Sintering (DMLS) process, or a multi jet fusion process.

III. Conclusion

[0174] The above detailed description sets forth various features and operations of the disclosed systems, apparatus, devices, and/or methods with reference to the accompanying figures. The example embodiments described herein and in the figures are not meant to be limiting, with the true scope being indicated by the following claims. Many modifications and variations can be made without departing from its scope, as will be apparent to those skilled in the art. Functionally equivalent systems, apparatus, devices, and/or methods within the scope of the disclosure, in addition to those described herein, will be apparent to those skilled in the art from the foregoing descriptions. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations. Such modifications and variations are intended to fall within the scope of the appended claims. Finally, all publications, patents, and patent applications cited herein are hereby incorporated by reference for all purposes.