TECHNICAL FIELD

The present invention relates to a system in a radio network node, more particularly, to a system in a radio network node for regulating temperature of electronic equipment within the radio network node. Moreover, the present invention relates to an arrangement for restricting flow in a heat exchanger unit.

BACKGROUND

Generally, a radio communication system of today comprises a radio access network and a number of communication devices. The radio access network is built up of several nodes, in particular, radio base stations. The primary task of a radio base station is to send and receive information to/from the communication devices within a cell served by the radio base station. In many cases, the base station is run 24 hours a day. Therefore, it is of particular interest and importance to ensure that the base station is operable predictably and reliably. The radio base station further comprises a cabinet, which comprises an enclosure for housing circuitry, or electronic equipment, for performing different tasks of the radio base station. For example, the circuitry may comprise a power control unit, a radio unit, comprising a radio amplifier, and a filtering unit for performing corresponding tasks.

Due to low efficiency in the radio amplifier of the radio base station, heat generated in the circuitry of the base station, in particular the radio unit, may not always dissipate naturally to a sufficiently high degree. Instead, heat is accumulated in the circuitry and temperature of the circuitry increases. The increased temperature of the circuitry may decrease the performance of circuitry within the radio base station, e.g. the circuitry within the radio base station may fail. Consequently, unpredicted interruptions in operation of the base station may occur. This is clearly not desired. Hence, as is known in the art, systems for cooling of heat generating equipment within a radio base station have been developed. These systems are sometimes referred to as climate systems or climate control systems for radio base stations.

An example of such a system for cooling of heat generating equipment is described below. The system comprises fans, which are used to circulate air through or over the heat generating equipment and through or over one side of a heat exchanger, i.e. an internal side within the enclosure. Moreover, further fans are used to force ambient air through or over the other side of the heat exchanger, i.e. an external side within the cabinet. The heat exchanger comprises a refrigerant that absorbs heat from air, heated by the electronic equipment, at the internal side within the enclosure. As a result, a transition from liquid phase to gas phase of the refrigerant occurs. The portion of the heat exchanger that is located at the internal side within the enclosure is called evaporator. The gas is forced to the external side of the heat exchanger, where it dissipates heat to ambient air. As a result, a transition from gas phase to liquid phase of the refrigerant occurs in the external side of the heat exchanger. The portion of the heat exchanger that is located on the external side is called condenser. At this stage, gravity forces the liquid to flow towards the evaporator. This kind of heat exchanger is generally denoted a thermosiphon.

A disadvantage with this kind of system, which comprises a thermosiphon, is that the electronic equipment may become unnecessary cold during, for example, cold weather conditions. As a result, performance of the electronic equipment is impaired.

SUMMARY

It is an object of the present invention to provide a system with a more reliable temperature regulation of the electronic equipment.

According to a first aspect of the invention, the object is achieved by a system in a radio network node for regulating temperature of electronic equipment within the radio network node. The system comprises a closed space comprising a flow generating device and the electronic equipment, wherein the flow generating device is arranged to circulate a first fluid within the closed space such that heat is transferrable between the electronic equipment and the first fluid. The system further comprises a heat exchanger unit, comprising an evaporator unit, a condenser unit, and a first and a second pipe. The evaporator unit is at least partly located within the closed space and the condenser unit is at least partly located outside the closed space. The first and second pipes are arranged to connect the evaporator unit and the condenser unit, whereby a loop is formed. A second fluid is flowable from the condenser unit to the evaporator unit in the first pipe and from the evaporator unit to the condenser unit in the second pipe. Furthermore, the system comprises a heater unit arranged at the first pipe and arranged to heat the second fluid in the first pipe such that flow in the first pipe is restricted, whereby temperature of the electronic equipment is regulated.

According to a second aspect of the present invention, the object is achieved by an arrangement for restricting flow in a heat exchanger unit. The heat exchanger unit comprises an evaporator unit, a condenser unit, and a first and a second pipe. The first and second pipes are arranged to connect the evaporator unit and the condenser unit, whereby a loop is formed. A second fluid is flowable from the condenser unit to the evaporator unit in the first pipe and from the evaporator unit to the condenser unit in the second pipe. Furthermore, the system comprises a heater unit arranged at the first pipe and arranged to heat the second fluid in the first pipe such that flow in the first pipe is restricted.

An idea of the invention is to reduce flow in the heat exchanger unit, whereby heat transportation to and/or from the electronic equipment via the first and second fluid is reduced. This is achieved by the system according to appended independent claim 1 and by the arrangement according to appended independent claim 5 by means of arranging a heater unit at the first pipe. In this manner, the system and the arrangement provide regulation of temperature of the electronic equipment without addition of any movable mechanical parts, such as valves or the like. As a result, a reliable system and a reliable arrangement are provided.

Advantageously, the heater unit provides for flow regulation of the second fluid while maintaining the same level of risk for leakage as before introduction of the heater unit. Moreover, the heater unit maintains the same level of flow resistance in the heat exchanger as before introduction of the heater unit. In other words, the heater unit does not introduce any pressure drop between the condenser unit and the evaporator unit.

A further advantage with the proposed solution is that heater units are readily and commercially available at low costs.

It is to be understood that the network node may be a radio base station or any other kind of node in a (radio) communication system, which node comprises heat generating electronic equipment. Examples of other kinds of nodes are transmission nodes, remote subscriber switches (RSS) and nodes with similar functionality.

Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. Those skilled in the art realize that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention, as defined by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The various aspects of the invention, including its particular features and advantages, will be readily understood from the following detailed description and the accompanying drawings, in which:

Fig. 1 shows a schematic block diagram of a system according to embodiments of the present invention, and

Fig. 2 shows a schematic block diagram of an arrangement comprising the heat exchanger unit in the system of Fig. 1.

DETAILED DESCRIPTION

Throughout the following description similar reference numerals have been used to denote similar elements, parts, items or features, when applicable. Fig. 1. shows a cross sectional, side view of a system 100 according to embodiments of the present invention. The system 100 in a radio network node 110 for regulating temperature of electronic equipment 120 within the radio network node 110 comprises a closed space 130, comprising a flow generating device 140 and the electronic equipment 120. The flow generating device 140 is arranged to circulate, as indicated by arrows 141 , 142, 143, 144, a first fluid within the closed space 130 such that heat is transferrable between the electronic equipment 120 and the first fluid. The arrow 144, in the vicinity of the electronic equipment 120, is dashed to indicate that the flow of the first fluid may pass through or over the electronic equipment 120. The arrow 142, at the flow generating device 140, is dashed to indicate that the flow is passed through the flow generating device 140. The system 100 further comprises a heat exchanger unit 200 arranged to transfer heat from the first fluid within the closed space 130 to ambient air outside the closed space 130. Optionally, a flow generating device 150 may be arranged to push or to direct ambient air through or over, as indicated by arrow 149, a portion of the heat exchanger 200 that is located outside the closed space 130. In this manner, excess heat from the electronic equipment 120 may be transported from the electronic equipment 120 to the first fluid within the closed space 130, from the first fluid to a second fluid comprised in and circulated within, as indicated by arrows 146, 147, the heat exchanger 200, and from the second fluid to, for example, ambient air.

Now with reference to Fig. 2, there is illustrated a block diagram of an arrangement 160 comprising the heat exchanger unit 200 in the system 100 according to Fig. 1. The heat exchanger unit 200 comprises an evaporator unit 202, a condenser unit 203, and a first and a second pipe 204, 205. The evaporator unit 202 is at least partly located within the closed space and the condenser unit 203 is at least partly located outside the closed space. The first and second pipes 204, 205 are arranged to connect the evaporator unit 202 and the condenser unit 203, whereby a loop is formed. A second fluid, such as a refrigerant fluid or a coolant, is flowable from the condenser unit 203 to the evaporator unit 202 in the first pipe 204 and from the evaporator unit 202 to the condenser unit 203 in the second pipe 205. The arrangement 160 comprises a heater unit 201 arranged at the first pipe 204 and arranged to heat the second fluid in the first pipe 204 such that flow in the first pipe 204 is restricted. By restricting the flow in the first pipe 204 performance of the heat exchanger unit 200 is decreased. As a consequence, the temperature of the first fluid within the closed space 130 is increased. Hence, also temperature of the electronic equipment 120 is increased, i.e. temperature of the electronic equipment 120 is regulated. Since the second fluid in the first pipe 204 has a temperature that is close to saturation point (boiling point) of the second fluid, only a small amount of heat is needed in order to evaporate the second fluid. The evaporated second fluid, in gaseous phase, causes a flow in the opposite direction to the flow of condensed second fluid, in liquid phase, in the first pipe 204. Consequently, due to the counteracting flows in gaseous and liquid phase, respectively, speed of flow in the loop is decreased or even completely shut off.

When operating the system 100 of Fig. 1 the following steps are performed simultaneously or as a sequence, starting with any of the steps described below. As a first step, as indicated by arrow 211, the evaporator unit 202 evaporates the second fluid. As a result, a first flow, as indicated by arrow 212, of the second fluid from the evaporator unit 202 to the condenser unit 203 is generated. Next, the condenser unit 203 condenses, as indicated by arrow 213, the second fluid. Thereby, a second flow, as indicated by arrow 214, of the second fluid from the condenser unit 203 to the evaporator unit 202 is generated. The second flow is enhanced by gravitation. In a further step, the heater unit 201 heats the second fluid in the first pipe 204. Since the temperature of the second fluid is close to saturation point of the second fluid, only a small amount of heat transferred to the second fluid causes the second fluid to evaporate. As a result, a third flow, as indicated by arrow 215, of the second fluid is generated. In this manner, the third flow, which is directed in the opposite direction compared to the flow of the second fluid in liquid phase from the condenser unit 203 to the evaporator unit 202, reduces the overall flow of the second fluid in the loop. Consequently, the reduced overall flow of the second fluid in the loop reduces the amount of heat transferred between the electronic equipment and the second fluid. Hence, for example, cooling of the electronic equipment is reduced.

It may be noted that the heater unit may, alternatively or additionally, be arranged to heat the first pipe, which in turn heats the second fluid therein.

As mentioned above, the flow of the second fluid in the heat exchanger unit 200 indirectly affects the amount of heat transferred to and/or from the electronic equipment. Thus, in a still further step, the heater may, optionally, be controlled by a controller (not shown), whereby temperature of electronic equipment comprised in the radio network node may be controlled.

Moreover, in some embodiments of the system according to the present invention, the heat exchanger unit 200 comprises a thermosiphon. It is preferred that resistance of or air pressure difference over the thermosiphon is low. Advantageously, the flow generating device 140 may be operated at low power, i.e. the system may be energy efficient. However, sometimes undesired flows of ambient air through the heat exchanger (see arrow 149) may cause the heat exchanger to cool the electronic equipment 120 more than desired. The undesired flows of ambient air are generated by and dependent on external weather conditions. For example, a windy day may cause undesired cooling of the electronic equipment 120. The provision of a heater unit 201, as described above, allows for a reduction of (or possibly complete shut off of) the amount of heat transferred from the electronic equipment 120, thereby securing that operation of the electronic equipment 120 is not impaired.

In embodiments of the system according to the present invention, the condenser unit 203 is located at least partly above the evaporator unit 202. Expressed differently, the evaporator unit 202 and the condenser unit 203 are arranged in relation to each other such that the fluid thanks to gravity is passed from the condenser unit 203 to the evaporator unit 202. As a result, fluid evaporated in the evaporator unit 202 is allowed to pass upwards and fluid condensed in the condenser unit 203 is allowed to pass downwards, in accordance with commonly known principles of fluid dynamics.

In an example of the system according to embodiments of the present invention, the electronic equipment 120 and the flow generating device 140 are arranged such that heat is transferrable between the electronic equipment 120 and the first fluid, wherein the flow generating device 140 is arranged to circulate the first fluid within the closed space 130. More specifically, not shown in a Figure, the flow generating device 140 may be arranged next to and at the same level from ground as the heat exchanger unit 200 in an upper portion of the enclosed space 130. Alternatively, the flow generating device 140 may be arranged next to and at the same level from ground as the electronic equipment 120 in a lower portion of the enclosed space 130, while the heat exchanger unit 200 still is located in an upper portion of the enclosed space 130. A man skilled in the art may find other alternatives for arranging the electronic equipment 120 and the flow generating device 140 such that heat is transferable between the electronic equipment 120 and the first fluid.

Even though the invention has been described with reference to specific exemplifying embodiments thereof, many different alterations, modifications and the like will become apparent for those skilled in the art. The described embodiments are therefore not intended to limit the scope of the invention, which is defined by the appended claims.