Field of the invention

The invention relates to a building constructed for cooling electronic devices such as computer devices in a data center.

Background

A data center houses a large number of computer devices such as servers, usually in many parallel rows with racks of such devices located in a single room. As all these computer devices produce heat, the room requires a cooling capacity that is proportional to the number of computer devices. Conventionally a bank of air conditioning units is used to create a closed air circulation, wherein each air conditioning unit pumps air from the room through its heat exchanger and from there back into the room. In each air conditioning unit heat from the air of the data center is exchanged with outside air, to remove heat from the air of the data center.

Each air conditioning unit provides a maximum cooling capacity in terms of the amount of thermal energy that can be removed per unit time. For example an air conditioning unit may have a cooling capacity of 80 kW. When it is known how much thermal energy is produced by the servers when running at their maximum capacity, this makes it possible to compute the minimum number N of air conditioning units and their corresponding power supply facilities that are needed to cool the data center T. But in practice operation with a“running redundancy” is used wherein the number of air conditioning units is larger. This reduces the overall power

consumption, because the air conditioning units need not operate at maximum capacity, where they are not optimally efficient. Furthermore, use of more than the minimum number of air conditioning units increases robustness in that it ensures that the data center can keep operating during temporary unavailability of a limited number of its air conditioning units. However, this requires that power supply facilities are needed to allow each of the air conditioning units to operate at maximum capacity. This, and the additional investment cost of the overhead air conditioning units contributes to the cost of the data center.

WO2012137692 discloses a building with a computer in data center. A cold aisle and a hot aisle are partitioned within the building. The air of the cold aisle flows trough a computer to the hot aisle. A cooling device cools air from the hot aisle, which is returned to the cold aisle. A second flow path installed inside the hot aisle is used to provide for heat exchange with outside air, to cool the air inside the hot aisle and thereby reduce the output needed from the cooling device.

Summary

Among others it is an object to provide for more cost effective efficient and robust air cooling of a room that contains a large number of heat producing computer devices.

A building according to claim 1 is provided.

By using heat exchange pipes in communication with the collection spaces for warm air from all pains of rows the number of excess fans needed to provide for robustness against failure can be reduced. Less overhead is needed to optimize power efficiency. In an embodiment the first array of fans is located along the first side wall, between the second air collection space and a part of the first room that contains the racks. This provides for the possibility of using a large number of fans. i.e. more than the minimum needed to drive the air flow when the fans operate at maximum capacity. Preferably, the part of the first air collection space extends substantially along all of the second wall. When the racks have distinguishable cold air inlets and heated air outlets on opposite sides, they are preferably all arranged with their outlets downstream from the inlets in direction of the air flow from the second air collection space to the first air collection space.

In an embodiment the heat exchange pipes extend substantially over a length equal to a distance between the first and second wall. The remainder of the length may be taken up by connections between the heat exchange pipes and the air collection spaces. Preferably the distance between the first and second wall is no longer than needed to cool down the air along each heat exchange pipe by ninety percent of the difference between the temperature of the air at the input of the heat exchange pipes on the side of the first air collection space and the outside air supplied to the heat exchange room.

In an embodiment the racks are arranged in rows extending in a length direction of the server room from the first wall of the server room to the second wall of the server room. In an embodiment air flow channels are provided, each from a closed off space between the rows of a respective pair of the rows to the first air collection space, the first air collection space being configured to collect air from all of the flow channels, the circuit running from the second air collection space to the server room outside the intra pair spaces, through the racks into the intra pair spaces and via the air flow channels to the first air collection space.

In an embodiment an air distribution space is provided located underneath a floor of the server room, the air distribution space being in communication with or forming a part of the second air collection space, i.e. the source of cold air, the floor containing openings for allowing air to flow selectively from the air distribution space to closed off spaces between rows in each of the respective pairs, the circuit running from the distribution space to the intra pair spaces and via the racks into the server room. In other words, a building is provide d that contains closed off spaces within a server room horizontally adjacent racks of computer devices. A first air collection space that extends to a side wall of the server room collects air that has flown through the racks. A second air collection space extends from an opposite side wall. A heat exchange room is provided above or below the server room. In the heat exchange room, heat exchange pipes are used to cool air flow from the first air collection space to the second air collection space and said part of the second air collection space. A first array of fans is arranged to drive a first air flow in a circuit from the second air collection space through the racks to the first air collection space and back to the second air collection space via the heat exchange room. A second array of fans drives a second air flow, of air from outside the building through the heat exchange room in counter flow with the first air flow, one of the first and second airflows flowing through the heat exchange pipes and the other flowing through the heat exchange room outside the heat exchange pipes.

Brief description of the drawing

These and other objects and advantageous aspects will become apparent from a description of exemplary embodiments with reference to the following figures.

Figure 1 shows a floor plan of a room containing racks of computer devices

Figure 2 shows a first cross-section including a room containing racks of computer devices

Figure 3 shows a second cross-section of a room containing racks of computer devices

Figure 4 shows a cross-section of an alternative building, with a so called Cold-Aisle containment Detailed description of exemplary embodiments

Figure 1 shows a floor plan of a server room 10 filled with rows of racks 12 of computer devices. On a first side of server room 10 an array of fans 14 is provided, between an air collection space 36 adjacent a first side wall 10b and the part of server room 10 wherein racks 12 are located, for blowing air from a first side wall 10a of server room 10 towards an opposite, second side wall 10b of server room 10 (for blowing the air in the indicated X direction). The array of fans 14 may extend substantially along the full width of server room 10 (along the indicated y direction). As used herein, “substantially extending” over the width refers to extending over at least the part of the width where rows are present. The relative dimensions of the server rooms and the rows are not shown realistically. In practical examples, a server room may be thirty five meters long in the x-direction and twelve to fifteen meters wide in the y-direction.

Within server room 10, closed off spaces 13 are formed between pairs of rows of racks 12. Closed off spaces 13 are closed off from the remainder of server room 10, except for air flowing through the computer devices. Between different pairs of rows there are open spaces, i.e. spaces that are in direct communication with the remainder of server room 10. Closed off spaces 13 promote that, in server room 10, air that has flown through the computer devices does not mix with air that has not yet flown through the computer devices. Although three pairs of rows are shown by way of example, it should be appreciated that in practice many more pairs may be used in the same server room, for example seven pairs of rows, with fifteen racks 12 in each row. Air flow from fans between rows of different pairs is possible. Racks 12 are permeable to air flow through the racks that cools the computer devices. Direct air flow from fans 14 into the intra pair spaces between rows of racks 12 is blocked by air flow closures for each respective pair of rows of racks 12. Some types of racks 12 may have distinguishable cold air inlets and heated air outlets on opposite sides for racks 12, e.g. in racks 12 wherein fans (shown) are provided within racks 12. When such a type of rack 12 is used, racks 12 in both rows of a pair rack 12 have their outlets discharging into the closed of space 13 between the rows and inlets taking up air from outside the pair.

Figure 2 shows a cross-section in a plane parallel to the first and second side walls 10a, b of server room 10 (i.e. in the YZ plane, where the z direction is the vertical direction, as indicated). The cross-section includes a cross-section of server room 10, a cross-section of a first air collection space 22 above server room 10 and a cross-section of a heat exchange room 20 above first air collection space 22. Air flow channels 24 (“chimneys 24”) are provided, each from the closed off space 13 between rows of racks 12 of a respective pair of rows of racks 12 in server room 10 to first air collection space 22, closed off from air in the remainder of server room 10, except for flow from the closed off space 13 between the pair of rows of racks 12. A plurality of heat exchange pipes 32 is provided in heat exchange room 20, preferably in a plurality of layers of heat exchange pipes 32, the layers containing heat exchange pipes 32 substantially over the whole width of heat exchange room 20. Between heat exchange pipes 32 there is space for flow of external air.

Figure 3 shows a cross-section in a plane perpendicular to the first and second side walls 10a, b of server room 10. For the sake of illustration the figure shows both a row of racks 12 and a cross-section of a chimney 24, although of course these are not intersected by a single plane, since chimney 24 is located above the space between a pair of rows of racks 12. Like figure 2, the cross-section includes a cross-section of server room 10, a cross-section of a first air collection space 22 above server room 10 and a cross-section of a heat exchange room 20 above first air collection space 22. First air collection space 22 has a part adjacent second side wall, and may extend in the X direction over substantially the entire length of server room 10 (as used herein substantially extending over the length refers to extension over at least 80%). Adjacent second side wall 10b a first opening 30 through the floor of heat exchange room 20 is provided, which allows air to flow from first air collection space 22 to heat exchange room 20. First opening 30 extends in the x direction only over a fraction of the length of server room 10 (e.g. no more than ten percent). Heat exchange room 20 contains heat exchange pipes 32 in air communication with first opening 30. As shown heat exchange pipes 32 may have a circular cross-section.

Alternatively, pipes with other cross-sections may be used e.g. polygonal cross sections like rectangular or triangular cross-section. The space in heat exchange room 20 between heat exchange pipes 32 is closed off from first opening 30. For the sake of illustration the closing off is symbolized by rounded heat exchange pipes 32 that extend to first opening 30, where they may be connected to a plate that closes off the space in heat exchange room 20 between heat exchange pipes 32, and with holes in the plate that pass air from first opening 30 to heat exchange pipes 32. Instead of holes in a plate, holes in the floor of heat exchange room 20 may be used. But preferably, heat excharge pipes 32 are just straight pipes, attached to a vertical plate with the same function. Alternatively flexible tubes may be used to connect straight heat exchange pipes 32 to such a plate in first opening 30. Any other type of connections may be used. For example, an air distribution box may be located at an end of in heat exchange room 20. In this embodiment, the air distribution box is in communication with first air collection space 22 via first opening or openings.

Adjacent first side wall 10a a connection between heat exchange pipes and a second opening 34 or openings 34 through the floor of heat exchange room 20 is provided, which allows air to flow from heat exchange pipes 32 to a second air collection space 36 between first side wall 10a and fans 14. Second air collection space 36 is closed off from the space in heat exchange room 20 between heat exchange pipes 32. The heat exchange pipes 32 may be connected to a second opening 34 or openings 34 in any of the ways described for the second end.

An array of further fans 38 is arranged between an inlet 39a for outside air at first side wall 10a and the space in heat exchange room 20 between heat exchange pipes 32. The array of further fans 38 may extend substantially along the full width of server room 10. An outlet 39b is provided at second side wall 10b, from the space in heat exchange room 20 between heat exchange pipes 32.

In operation separate internal and external air flows are created. The internal air flow is driven by fans 14. Fans 14 blow the internal air flow into server room 10, from where the internal air flow flows to first air collection space 22 through racks 12 and chimneys 24. From first air collection space 22 the internal air flow flows back to fans 14 through first opening 30, heat exchange pipes 32, second opening 34 and second air collection space 36 between first side wall 10a and fans 14.

The external air flow is driven by further fans 38 and flows from outside through inlet 39a, the space in heat exchange room 20 between heat exchange pipes 32 and outlet 39b. As may be noted the internal and external air flows flow in opposite directions in heat exchange room 20. As a result, counterflow heat exchange occurs between the internal air flow in heat exchange pipes 32 and the external air flow in the space in heat exchange room 20 between heat exchange pipes 32. As a result, when the air in the internal air flow that enters heat exchange room 20 is warmer than air in the external air flow that enters heat exchange room 20, the

counterflow heat exchange cools the internal heat flow.

It has been found that it is possible to realize the required amount of cooling with a practically feasible air flow speed and height of heat exchange room 20. When the length of heat exchange room 20 is sufficient to cool the internal air flow to near ambient temperature (e.g. more than ten meters), the cooling capacity of heat exchange room 20 is proportional to the product of its width, its height and the internal air flow volume. On the other hand, the heat production by the racks is proportional to the width of server room 10, which is substantially the same as the width of heat exchange room 20. Therefore, for a given density of rows of racks, the cooling capacity can be matched to the heat production only by selection of the height and the internal air flow volume of heat exchange room 20.

It has been found that feasible height values and internal air flow volume values suffice to realize the required cooling capacity. In an illustrative example, about every five and half meter width of the data center contains one pair of racks. Current racks produce about five kilo Watt heat per rack. For a length of server room 10 that corresponds to a length of heat exchange pipes 32 that is sufficient to enable cooling the internal air flow to near ambient temperature , a row may contain fifteen racks for example, so that a hundred fifty kilo Watt of heat is produced in every five and a half meter of the width (i.e. about twenty five kW per meter width). A typical minimum value of the air temperature decrease form the input to the output of the heat exchanger is about nine degrees. The amount of heat that can be removed from the air, with such a temperature change is about eleven kilo Joule/m3. This means that an air flow volume of about two and a half cubic meters air from the data center per second is needed per meter width of heat exchange room 20. This can easily be realized when heat exchange room 20 is about one meter high. When heat exchange pipes 32 of eighty millimeter diameter used, about a hundred heat exchange pipes 32 can be user per meter width, when heat exchange room 20 is one meter high. In this case, an air flow of about 0.025 cubic meters per second is needed per pipe. With such heat exchange pipes 32 an air flow of about five meter per second is sufficient to achieve this volume. This air flow speed can be realized with a pressure drop of about sixty Pascal along the heat exchanger, which can easily be realized using fans 14.

The arrangement of first air collection space 22 and heat exchange pipes 32 is configured so that the internal air flow from each of chimneys 24 can reach each of heat exchange pipes 32 directly on the side of second side wall 10b (directly in the sense that the air can reach each heat exchange pipe 32 without having to flow through any other of the heat exchange pipes 32). Similarly, the arrangement of heat exchange pipes 32 and fans 14 is configured so that the part of the internal air flow through each of heat exchange pipes 32 can directly reach any of fans 14.

As a result all heat exchange pipes 32 will contribute to cooling when any individual fan 14 fails. The cooling can be made robust against fan failure by using more fans 14 than strictly needed for cooling aB racks 12. As the passive heat exchange pipes 32 are less prone to failure, no significant excess capacity of heat exchange pipes 32 is needed for

robustness. Rather, the choice of the number of pipes affects the pressure drop over the heat exchanger, and hence the required fan power. In an embodiment, a redundant control system and a redundant power supply system are provided for driving the fans. The redundant control system comprises a plurality of control circuits, configured so that any one of the fans can be controlled by a plurality of the control circuits. Similarly, the redundant power supply system comprises a plurality of power supply circuits, configured so that any one of the fans can receive power from a plurality power supply circuits. This ensures that cooling operation will not fail when a single control circuit or power supply circuit fails.

Power input is needed to realize the cooling because fans 14 and further fans 38 need to be driven, usually by means of electric current. The amount of needed power input depends on the air pressure drop that needs to be overcome, mainly in the internal air flow. In turn, this pressure drop is affected by the pressure drop over heat exchange pipes 32. Because these heat exchange pipes 32 are located in a separate heat exchange room 20 above server room 10, that has the same width and length, the number and/or diameter of heat exchange pipes 32 can be made large, so as to decrease the pressure drop over heat exchange pipes 32 for a given volume of flow of the internal air flow. This reduces the input power needed for cooling. In the preceding illustrative example an air flow volume of about two and a half cubic meters air from the data center per second is used per meter width of heat exchange room 20, caused by a pressure drop of about sixty Pascal along the heat exchanger. Such a pressure drop can be realized by means of about 0.5 kW fan power per meter width. The fan power needed for the outside air is about 0.9 kW per meter width. Thus, about 1.4 kW per meter to remove about twenty five kW of heat per meter width.

As noted, the length of heat exchange room 20 (i.e. the length of server room 10) is preferably chosen so that the internal air will be cooled substantially to ambient temperature in heat exchange room 20, e.g. at least ten meters. The optimal length may depend on the flow speed and the diameter of heat exchange pipes 32 that are used. But if the length is smaller the heat production per meter with is also smaller, because fewer racks can be used per row, so that the smaller length may suffice. Moreover, a smaller pressure drop will be needed, so that the number of fans can be reduced. Preferably the distance between the first and second wall is no longer than needed to cool down the air along each heat exchange pipe by ninety percent of the difference between the temperature of the air at the input of the heat exchange pipes on the side of the first air collection space and the outside air supplied to the heat exchange room.

On the other hand, when the length of server room 10 is much larger, the rows may be longer, an d the heat production per meter width increases in proportion to the length. In this case, the cooling capacity of heat exchange room 20 cannot be scaled in proportion. Therefore, it is preferred to avoid making server room 10 much longer than the length over which the internal air will be cooled substantially to ambient temperature. The length of server room 10 may be divided into separated sections, each with its own heat exchange system, to ensure that the length of each section is not so larger that the cooling capacity is exceeded.

Overall, it is possible to avoid bottlenecks that could make it necessary to increase the required pressure drop. The openings 30, 34 to and from heat exchange room 20 may extend over substantially the full width of server room 10, i.e. in proportion to the number of rows of racks 12.

In the described embodiment server room 10 and heat exchange room 20 are rooms that are vertically aligned, i.e. their vertical projections on a horizontal plane substantially coincide, so that they have substantially the same width and length and are substantially co-extensive in horizontal cross-sections. The walls of the server room 10 and heat exchange room 20 may be vertically aligned. This facilitates building. The rooms may be constructed first and the heat exchanger in the heat exchange room 20 may be assembled later in situ in the heat exchange room 20, using generally available straight pipes.

An embodiment has been described wherein first air collection space 22 is located above server room 10 and heat exchange room 20 is located above first air collection space 22. This has the advantage that the hot internal air flow naturally tends to flow upward from the closed off space 13 between rows in pairs of rows of racks 12 through chimneys 24 to first air collection space 22, so that a sufficient pressure drop can be create by fans 14 using a minimum of input power. But alternatively, server room 10, first air collection space 22 and heat exchange room 20 may be arranged in any order. Also, although only first air collection space 22 is shown between the aligned server room 10 and heat exchange room 20, it should be appreciated that other spaces, such as spaces for supporting equipment, storage etc. may be located between the aligned server room 10 and heat exchange room 20. Although an embodiment has been shown wherein cold air is blown into the part of the server room outside the pairs of rows and heated air is collected from the spaces between the rows in the pairs, the role of part of the server room outside the pairs and the spaces between the rows in the pairs could be reversed, cold air being blown into the spaces between the pairs and heated air being collected from the part of the server room outside the pairs.

Figure 4 shows an embodiment wherein cold air is introduced between the rows of each pair from an air distribution space 40 below the floor of server room 10, though openings in the floor of server room 10 between rows in each pair of rows. Flow of air from between the rows in the pair that circumvents the racks is blocked. The air flows through the racks into the room. In this embodiment, the part of room 10 outside the pairs of rows acts as the first air collection space. The air flows from this space to heat exchange room 20 at the second end of the server room through an opening (not shown) located like opening 30 of figure 3. Air that has flown through heat exchange room 20 flows down past server room 10 to air distribution space 40 through a passage (not shown) at the first end of server room 10, at a position like that of second air collection space 36 of figure 3. Air distribution space 40 may be used as second air collection space together with, or instead of, space 36. When a type of racks 12 with distinguishable cold air inlets and heated air outlets is used, racks 12 in both rows of a pair rack 12 have their inlets taking up air from the closed of space between the rows and outlets discharging air outside the pair.

An embodiment has been described wherein first air collection space 22 extends over substantially the full width and length of server room 10 without internal separation. This too helps to reduce the required input power. But alternatively, the first air collection space 22 per se may be located only adjacent the second side wall 10b extending over only a fraction of the length of server room 10, with separated sub- collection spaces, along different pairs of rows of racks 12, discharging into the first air collection space per se. Thus first air collection space 22 is still configured so that the internal air flow from each of chimneys 24 can reach each of heat exchange pipes 32 directly. In yet another embodiment the first air collection space may be located in the heat exchange room, between the second side wall and the heat exchange pipes. In this case the separated sub-collection spaces may extend to the first opening 30.

Similarly, although an embodiment has been shown wherein chimneys 24 extend over substantially the full length of server room 10, alternatively separate chimneys 24 may be used for respective parts of a pair of rows of racks 12. Also similarly, although space 36 between first side wall 10a and fans 14 preferably extends substantially over the full width of server room 10, alternatively separations may be present in part of this space.

Although an embodiment has been shown wherein the array of fans 14 is located adjacent the first side wall of server room 10, alternatively fans 14 may located elsewhere in the flow circuit of the internal air flow, or at a plurality of locations in this circuit. Similarly, although an embodiment has been shown wherein the array of further fans 38 is located at the front of the flow circuit of the external air flow, further fans 38 may be located elsewhere in that flow circuit, or at a plurality of locations in this circuit.

Although an embodiment has been shown wherein the internal air flow flows through heat exchange pipes 32 and the external air flow flows through the surrounding of heat exchange pipes 32, it should be appreciated that alternatively the internal air flow may flow through the surrounding of heat exchange pipes 32 and the external air flow flows through heat exchange pipes 32. Use of an internal air flow through heat exchange pipes 32 makes it easier to supply the external air flow separated from the internal air flow.

Embodiments have been described wherein the racks are arranged in rows along the direction of air flow in server room 10 (the x-direction), with closed off spaces 13 between pairs of rows and air flow through the computer devices transverse to the x-direction (e.g. perpendicular to the x- direction and in any case not parallel). Preferably, the longest horizontal direction of the racks 12 is in the the x-direction as well. This minimizes unnecessary obstruction of the air flow. However, alternatively the racks may fill server room 10 in other ways, e.g. in a periodic grid of positions of isolated racks with shields to form the closed-off spaces next to the isolated racks, in isolated pairs of racks with closed-off spaces in between, or in groups of racks that enclose common closed off inner spaces (e.g. squares or other polygonal spaces).

In each case the racks fill the server room in the sense that the number of racks increases in proportion with the surface area of the server room to create a substantially predetermined density of racks. The density is defined as a ratio between the combined footprint of the racks (the sum of their areas in cross-section with a horizontal plane) and the overall floor area of server room 10. A typical minimum density at which the server room is filled with racks allows for the footprint and areas with the same size as the footprint on both sides of the rack, i.e. a density of at least 1/3.

In a further embodiment optionally an adiabatic humidifier may be included upstream from the heat exchange room in the flow of outside air to humidify the external air flow before it flows to the heat exchange pipes (an adiabatic humidifier ensures that the initial dry bulb temperature of the outside air in the heat exchange room is lowered). This increases the amount of heat that can be removed from the internal air flow. Optionally, a temperature and/or enthalpysensor arranged to sense the temperature and/or enthalpy of the outside air is used to control humidifying the outside air only if its temperature exceeds a preset threshold. It has been found that the heat exchange is so efficient that at the most frequent outside

temperatures is not needed for current server hardware. So for buildings in sufficiently cool environments adiabatic humidification may be omitted.