WO2010050873A1

WO2010050873A1 - A system in a network node for regulating temperature of electronic equipment

Info

Publication number: WO2010050873A1
Application number: PCT/SE2009/050181
Authority: WO
Inventors: Fredrik Jonsson
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2008-11-03
Filing date: 2009-02-18
Publication date: 2010-05-06
Also published as: WO2010050868A1

Abstract

A system (100) in a radio network (110) node for regulating temperature of electronic equipment (101) within the radio network node (110) is provided. The system (100) comprises a flow regulating device (104) for circulating a refrigerant, a chamber (102) for receiving the refrigerant from the flow regulating device (104). The chamber (102) has an inlet (108) and an outlet (109). Furthermore, the system (100) comprises a heat exchanger unit (105) for exchanging heat with the refrigerant, wherein the heat exchanger unit (105) is connected to the outlet (109) of the chamber (102) and to the flow regulating device (104). Moreover, the chamber (102) and the electronic equipment (101) are arranged such that heat is transferrable between the electronic equipment (101) and the refrigerant, when the refrigerant is received by the chamber (102) via the inlet (108).

Description

A SYSTEM IN A NETWORK NODE FOR REGULATING TEMPERATURE OF ELECTRONIC EQUIPMENT

TECHNICAL FIELD The present invention relates to a system in a network node, more particularly to a system in a radio network node for regulating temperature of electronic equipment within the radio network node.

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 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. According to a first technique for cooling of heat generating equipment, fans are used to circulate air through or over heat generating equipment and through or over one side of an air to air 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 air to air heat exchanger (i.e. an external side). Within the heat exchanger, heat is transferred from air at the internal side within the enclosure to air at the external side.

According to a second technique for cooling of heat generating equipment, fans 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). The heat exchanger comprises a refrigerant that absorbs heat from the 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, by evaporation, 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.

Furthermore, similar to the second technique mentioned above, the evaporator may be connected directly to the heat generating equipment. In this case, there is no need for fans inside the enclosure, since no air need to be circulated within the enclosure.

As a further method for cooling heat generating equipment, it has been proposed to use a cooling machine in combination with air circulation on an internal and an external side of the enclosure as is described in conjunction with the second technique above. The cooling machine is basically a kind of refrigerator. A basic refrigerator comprises a compressor, an expansion valve, an evaporator, a condenser and piping. A closed circuit is formed by the components in series as follows: compressor, condenser, expansion valve and evaporator. The components are connected with metal pipes and/or high pressure hoses. When operating the refrigerator, the compressor compresses a refrigerant in gaseous phase from the evaporator (a so called low pressure side). Then, the refrigerant is lead to the condenser (a so called high pressure side) where it dissipates heat to ambient air. Next, the refrigerant changes phase from gas to liquid. Thereafter, the refrigerant passes through the expansion valve and is directed into the evaporator, where it absorbs heat. As a result, the refrigerant yet again changes phase from liquid to gas, i.e. it is evaporated.

A yet further known technique for cooling of heat generating equipment is based on using ambient air as cooling medium. When using ambient air as a cooling medium, the air is pushed by means of fans into the enclosure in which the heat generating equipment is located. The air flow is directed through and/or over the heat generating equipment, and then the air flow is forced out of the enclosure by means of at least one fan. In order to improve this technique, filters have been arranged at the inlets to the enclosure, thereby avoiding particles, chemicals and dust or alike to enter the enclosure.

The above mentioned techniques suffer from poor effectiveness in transferring heat from the heat generating equipment within the enclosure to air outside of the enclosure.

SUMMARY

It is an object of the present invention to improve efficiency of heat transfer between electronic equipment within a radio network node and a medium for transporting heat.

According to an 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 flow regulating device for circulating a refrigerant, a chamber for receiving the refrigerant from the flow regulating device. The chamber has an inlet and an outlet. Furthermore, the system comprises a heat exchanger unit for exchanging heat with the refrigerant, wherein the heat exchanger unit is connected to the outlet of the chamber and to the flow regulating device. Moreover, the chamber and the electronic equipment are arranged such that heat is transferrable between the electronic equipment and the refrigerant, when the refrigerant is received by the chamber via the inlet.

An idea of the invention is to provide an improved system for regulating temperature of electronic equipment by using a chamber that is arranged to receive a refrigerant and that is arranged such that the refrigerant may transfer heat from or to the electronic equipment. Within the system, the chamber and the electronic equipment are arranged such that heat is transferrable between the electronic equipment and the refrigerant, when the refrigerant is directed into the chamber. In this manner, the temperature of the electronic equipment may be regulated and efficient heat transfer to and/or from the electronic equipment is provided. Furthermore, an advantage with the system according to the present invention is that the need for use of large and heavy cooling fins (or flanges), arranged at the electronic equipment, is eliminated or at least reduced, since the refrigerant provides for a more efficient heat transfer to/from the electronic equipment than prior art systems. As a result, the heat transfer capacity per unit of weight and/or volume is improved as compared to most prior art systems. In addition, an advantage compared to prior art systems using an evaporation unit of a thermosiphon in contact with the electronic equipment is that the proposed solution has superior heat transferring capability. For example, in such a prior art system the heat transfer coefficient is approximately 200 - 40 000 WAn²K, whereas the heat transfer coefficient for a system according to the proposed solution is approximately 20 000 - 10 000 000 WAn²K.

It is to be noted that the refrigerant may be any liquid suitable for transferring heat between the electronic equipment and the liquid.

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 Mobility Management Entities (MME), Operation and Support Systems (OSS), Remote Subscriber Switches (RSS) and nodes with similar functionality. The electronic equipment may be configured to handle filtering functions in the radio network node. The flow regulating device may, for example, be a pump or a compressor. It may be preferred that the flow regulating device is able to create a pressure that allows the refrigerant to form a spray, when injected into the chamber.

The electronic equipment may be enclosed by the chamber. In this manner the refrigerant may be directed or sprayed onto the electronic equipment via the inlet. Alternatively, the electronic equipment may be located outside the chamber. Any problems with the refrigerant penetrating into the electronic equipment may be avoided while heat exchange with the refrigerant inside the chamber may still take place.

The system may further comprise an injecting device arranged at the inlet of the chamber and arranged to inject the refrigerant such that heat is transferrable between the electronic equipment and the refrigerant. The injecting device may be a nozzle. A nozzle may be advantageous in shaping and directing the refrigerant to reach desired locations inside the chamber.

The injecting device may be arranged to spray the refrigerant into the chamber. By spraying the refrigerant a high heat transfer from the electronic equipment to the refrigerant can be achieved. Alternatively, the inlet may be arranged to direct the liquid into the chamber to permit the liquid to flow though the chamber in an essentially continuous flow or an intermittent flow. An advantage of letting the refrigerant flow through the chamber is that it is can easily be administered into and through the chamber while good heat transfer between the electronic equipment and the refrigerant takes place.

The inlet of the chamber may be arranged at a same level as or at a higher level than the outlet to allow gravity induced flow of liquid through the chamber. The refrigerant will thus naturally be lead to a heat exchanger unit arranged at a level lower than at least part of the chamber.

The heat exchanger unit may be arranged for heat exchange between the refrigerant and air. For instance, outside air may be a suitable cooling fluid for cooling the refrigerant inside the heat exchanger by passing through or over the heat exchanger. The air may be passed through or over the heat exchanger by a fan constituting a flow regulating device for the air.

In the system the network node may comprise an enclosed space, in which the electronic equipment is arranged, and wherein at least the chamber of the system is arranged inside the enclosed space and at least the heat exchanger unit of the system is arranged outside the enclosed space. With this arrangement the heat exchanger unit suitably is arranged for heat exchange with air ambient of the enclosed space, e.g. outside air.

The system may comprise a refrigerant collection vessel arranged in a part of a refrigerant circuit of the system including the chamber, the heat exchanger unit and the flow regulating device, wherein the refrigerant collection vessel is adapted to act as a buffer for liquid refrigerant. It is thus ensured that there is a sufficient amount of refrigerant in the system to ensure cooling of the electronic equipment in all situations.

The system may further comprise a control unit, connected to flow regulating devices for controlling flow of the refrigerant and/or a cooling fluid passing through or over the heat exchanger unit, wherein the control unit is arranged and configured to control flow of the refrigerant and/or the cooling fluid based on

- temperature of the electronic equipment, temperature of a wall of the chamber, temperature of the refrigerant in vapor phase,

- temperature of the refrigerant in liquid phase, - temperature of a point at a pipe circuit, wherein the pipe circuit is arranged to connect the flow regulating device, the chamber and the heat exchanger unit, pressure in a pipe circuit, wherein the pipe circuit is arranged to connect the flow regulating device, the chamber and the heat exchanger unit, temperature of the heat exchanger, temperature of the cooling fluid that is to be passed through and/or over the heat exchanger, wherein the heat exchanger is arranged to transfer heat between the cooling fluid and the refrigerant, and a pipe circuit is arranged to connect the flow regulating device, the chamber and the heat exchanger unit,

- the temperature of the cooling fluid that has passed through and/or over the heat exchanger, wherein the heat exchanger is arranged to transfer heat between the cooling fluid and the refrigerant, and a pipe circuit is arranged to connect the flow regulating device, the chamber and the heat exchanger unit, the temperature of a cooling fluid, being in non-contact with the heat exchanger, wherein the heat exchanger is arranged to transfer heat between the cooling fluid and the refrigerant, and a pipe circuit is arranged to connect the flow regulating device, the chamber and the heat exchanger unit, temperature of any item inside an enclosed space, wherein the radio network node comprises the enclosed space, and wherein the enclosed space comprises the electronic equipment and the system, or

- temperature of air inside an enclosed space, wherein the radio network node comprises the enclosed space, and wherein the enclosed space comprises the electronic equipment and the system, or

- a combination thereof.

A reliable regulation of the temperature of the electronic equipment may be achieved by utilizing the control unit to control the system based on any one or combinations of these parameters.

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 block diagram of a radio network node, comprising the system according to embodiments of the present invention,

Fig, 2 shows a schematic layout of a portion of the system according to some embodiments of the present invention, wherein the layout illustrates a chamber and electronic equipment located outside the chamber,

Fig. 3 shows a schematic layout of a portion of the system according to further embodiments of the present invention,

Fig. 4 shows a schematic layout of a portion of the system according to still further embodiments of the present invention, wherein the chamber at least partly surrounds the electronic equipment

Fig. 5 shows a partial block diagram of a radio network node, comprising the system according to embodiments of the present invention, and

Figs. 6 and 7 show schematic layout of a portion of the system according to further embodiments of the present invention.

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 system 100 in a radio network node 1 10 for regulating temperature of electronic equipment 101 within the radio network node 110. The system comprises a chamber 102 for receiving the refrigerant from the flow regulating device 104, a flow regulating device 104 for circulating a refrigerant. Furthermore, the system 100 comprises a heat exchanger unit 105 for exchanging heat with the refrigerant, the heat exchanger unit 105 being connected to an outlet 109 of the chamber 102 and to the flow regulating device 104. The chamber 102 has an inlet 108 and an outlet 109. Optionally, the system 100 may comprise a collection vessel 106 for collecting the refrigerant in the system 100. The use of the collection vessel 106 ensures that the flow regulating device 104 is fed with refrigerant in liquid phase, in contrast to refrigerant in gaseous phase. The collection vessel 106 may act as a buffer for liquid refrigerant. In Fig. 1 , the collection vessel 106 is located between the flow generating device 104 and the heat exchanger 105. Alternatively, the collection vessel 106 may be located between the chamber 102 and the heat exchanger 105. From the Figure, it may be seen that the chamber 102 and the electronic equipment 101 are arranged such that heat is transferrable between the electronic equipment 101 and the refrigerant, when the refrigerant is received by the chamber 102 via the inlet 108. Furthermore, in embodiments of the present system, the heat exchanger is arranged to be able to exchange heat with external fluid, such as (ambient) air.

With reference to Fig. 5, there is illustrated a radio network node 110 comprising an enclosed space 111 for holding and protecting the electronic equipment 101. A chamber 102, in which heat transfer between the electronic equipment 101 and the refrigerant directed into the chamber 102 takes place, is also arranged inside the enclosed space 111. Outside the enclosed space 111 the heat exchanger unit 105 is arranged. The heat exchanger unit 105 is thus arranged to exchange heat with air of an ambient environment of the enclosed space 111 , i.e. the refrigerant inside the heat exchanger unit 105 is cooled by ambient air. Remaining parts of the system for regulating temperature may be arranged inside or outside the enclosed space 111. Parts sensitive to environmental influences are suitably arranged inside the enclosed space 111. What parts are arranged inside or outside the enclosed space 111 may depend on what kind of refrigerant is being used and/or in what environment the radio network node 110 is installed. The refrigerant may for instance be water, to which an anti-freezing additive, e.g. glycol, may be added. The invention is not limited to use of a particular refrigerant and there are many alternatives to water, e.g. R134a (1 ,1 ,1 ,2-Tetraflouroethane), ammonia, etc. In the embodiments according to the systems shown in Figs. 1 and 5, the electronic equipment 101 is enclosed by the chamber 102. In this manner, the refrigerant may be directed or sprayed onto the electronic equipment via inlet 108. For the sake of simplicity, any means for protecting the electronic equipment 101 from the refrigerant such as to ensure proper function of the electronic equipment 101 have been omitted in Figs. 1 and 5.

In operation, the system 100 regulates the temperature of the electronic equipment by allowing heat to be transferred to and/or from the electronic equipment via the refrigerant. As a first step, the flow regulating device 104 pumps or forces the refrigerant to circulate in the system. The refrigerant is injected into the chamber 102 via inlet 108. Optionally, the inlet 108 may be arranged to direct a jet of refrigerant at the electronic equipment 101. As is described above, in exemplifying embodiments of the system according to the present invention, the chamber and the electronic equipment are arranged such that heat is transferrable between the refrigerant and the electronic equipment. The refrigerant may, on contact with the electronic equipment 101 , partially, evaporate. During certain conditions, no refrigerant at all is evaporated on contact with the electronic equipment 101. In general, not all of the refrigerant is evaporated on contact with the electronic equipment 101. In the following step, the refrigerant, possibly a portion thereof in gaseous phase, is passed via outlet 109 to the heat exchanger 105. The heat exchanger may exchange heat between the refrigerant within the system 100 and a cooling fluid, passed through or over the heat exchanger 105. Furthermore, further flow regulating devices (not shown) may regulate the flow of the cooling fluid through or over the heat exchanger 105. The cooling fluid may, for example, be ambient air.

The system 100 may further comprise a control unit 1 11 for controlling flow of the cooling fluid passing through or over the heat exchanger 105 and/or the refrigerant within the system 100. The control unit is connected to the flow regulating device 104 and to the flow regulating devices (not shown) for regulating flow of the cooling fluid. The control unit controls flow of the refrigerant and/or the cooling fluid based on

(1 ) temperature of the electronic equipment,

(2) temperature of a wall of the chamber, (3) temperature of the refrigerant in vapor phase,

(4) temperature of the refrigerant in liquid phase,

(5) temperature of a point at a pipe circuit, wherein the pipe circuit is arranged to connect the flow regulating device, the chamber and the heat exchanger unit,

(6) pressure in a pipe circuit, wherein the pipe circuit is arranged to connect the flow regulating device, the chamber and the heat exchanger unit,

(7) temperature of the heat exchanger, (8) temperature of a cooling fluid that is to be passed through and/or over the heat exchanger, wherein the heat exchanger is arranged to transfer heat between the cooling fluid and the refrigerant, and a pipe circuit is arranged to connect the flow regulating device, the chamber and the heat exchanger unit, (9) the temperature of a cooling fluid that has passed through and/or over the heat exchanger, wherein the heat exchanger is arranged to transfer heat between the cooling fluid and the refrigerant, and a pipe circuit is arranged to connect the flow regulating device, the chamber and the heat exchanger unit, (10) the temperature of a cooling fluid, being in non-contact with the heat exchanger, wherein the heat exchanger is arranged to transfer heat between the cooling fluid and the refrigerant, and a pipe circuit is arranged to connect the flow regulating device, the chamber and the heat exchanger unit, (11 ) temperature of any item inside an enclosed space, wherein the radio network node comprises the enclosed space, and the enclosed space comprises the electronic equipment and the system, or

(12) temperature of air inside an enclosed space, wherein the radio network node comprises the enclosed space, and the enclosed space comprises the electronic equipment and the system, or

(13) a combination thereof.

An advantage with controlling the flow of the refrigerant and/or the cooling fluid based on the temperature of the electronic equipment is that reliability and durability of the system may be improved if the temperature of the electronic equipment is maintained within a range which may be obtained from the specification of the electronic equipment.

If the temperature of the electronic equipment is not available, it may be advantageous to control the flow of the refrigerant and/or the cooling fluid based on items (2) - (6).

Item (7) may be the temperature of the refrigerant being fed onto the electronic equipment. In this manner, a good approximation of the temperature of the electronic equipment is obtained.

It is preferred to use items (8)-(10) in combination with at least one of items (1 ) - (7) and (11 ) - (12), whereby smooth control may be achieved, since, for example, temperature of ambient air, may be taken into account.

A further possibility of obtain a temperature close to the temperature of the electronic equipment is provided by item (11 ). In this manner, the control unit is fed with a temperature that inherently reacts more slowly to changes, i.e. some slack in the control system is introduced.

Item (12) is a cheap and simple way to obtain a rough approximation of the temperature of the electronic equipment.

A combination of at least two of items (1) through (12) allows a control unit that controls the temperature by using small amounts of energy for the flow regulating device and any fans present in the system.

In some embodiments of the system 100, the system 100 may comprise an injecting device 103 arranged at the inlet 108 of the chamber 102. The injecting device 103 is, preferably, arranged to inject (spray or direct) the refrigerant such that heat is transferrable between the electronic equipment 101 and the refrigerant. For example, the refrigerant may be directed or sprayed at the electronic equipment 101 or at a surface, which surface is in contact with the electronic equipment, thereby allowing heat to be transferred between the electronic equipment and the refrigerant. Advantageously, the injecting device (or a spraying device) 103 is a nozzle, whereby the selection of different types of nozzles may provide different kinds of shapes of the refrigerant directed at the electronic equipment. It may even be considered to use a nozzle that may direct the refrigerant at different parts of the electronic equipment 101. In this manner, localized temperature regulation may be achieved at different parts of the electronic equipment 101. In its most basic form, the injecting device 103 may be a more or less elaborately shaped opening of the inlet 108 leading to the chamber 102.

It may be noted that the injecting device 103 may be arranged to spray the refrigerant into the chamber as a result of a pressure difference over the injecting device 103. The pressure difference is generated by the flow generating device 104. Alternatively or additionally, a spray may be formed by means an ultra sonic device as is know in the art. Yet another option is to inject refrigerant into a flow of air, which is directed at the electronic equipment 101. Consequently, a spray is formed.

For typical embodiments of the system according to the present invention, wherein the refrigerant is sprayed into the chamber onto the electronic equipment, a heat transfer coefficient between 20 000 and 10 000 000 W/m²K is to be expected.

Moreover, in embodiments of the system 100, the electronic equipment may be configured to handle radio functions in the radio network node 110. Since radio functions generally requires more power than, for example, filtering functions, it may be advantageous to implement temperature regulation for these parts of the electronic equipment.

Referring to Fig. 2, there is shown a view over a portion of an exemplifying system according to embodiments of the present invention. Fig. 2 shows the following parts of the system: a chamber 102, a spraying device 103, electronic equipment 101 and a thermal via 201. As is well known, liquids may cause shorts cuts or other malfunctions, when in contact with electronic circuits. In the system, a portion of which is illustrated in Fig. 2, the electronic equipment 101 is located outside the chamber 102. In this manner, the refrigerant (within the chamber) is efficiently separated from the electronic equipment such as to ensure that no refrigerant may harm circuits of the electronic equipment. As a result, no additional precautions, such as providing insulating layers at the electronic equipment to ensure proper operation thereof, are needed.

In a further exemplifying embodiment (not shown) of the present system, the chamber 102, the injecting device 103 and the electronic equipment 101 are arranged such that the refrigerant is capable of transferring heat to and/or from the electronic equipment. This may be realized in many different manners, as is understood by the man skilled in the art and illustrated in Fig. 3. and 4.

In Fig. 3, there is demonstrated a first example of the present system, wherein the chamber 102, the injecting device 103 and the electronic equipment 101 are arranged such that the refrigerant is capable of transferring heat to and/or from the electronic equipment. The injecting device 103 and the inlet 108 are at one end of the chamber and the outlet 109 of the chamber is located at a distal position in relation to the injecting device 103 and the inlet 108. Furthermore, the volume of the chamber is decreased in comparison with the system depicted in Fig. 1 and/or 2. In this manner, the refrigerant may flow along the electronic equipment 101 such as to cover substantially the entire surface thereof. As a consequence, heat transfer between the electronic equipment and the refrigerant is improved. Moreover, the electronic equipment 101 is arranged outside the chamber 102, but in close contact therewith, and is arranged between the inlet 108 and the outlet 109, whereby the refrigerant passes the electronic equipment when the system is operated.

With reference to Fig. 4, there is indicated a second example of the present system, wherein the chamber 102, the injecting device 103 and the electronic equipment 101 are arranged such that the refrigerant is capable of transferring heat to and/or from the electronic equipment. In Fig. 4, the chamber 102 formed to at least partly surround or enclose the electronic equipment 101. For example, the chamber may be in the form of a double walled cup, wherein the volume of the chamber is formed between the walls of such cup. As a result, the temperature of the electronic equipment may be regulated efficiently, since heat may be transferred to and/or from the electronic equipment at several sides thereof. Fig. 6 illustrates a part of a system according to example embodiments of the invention. An inlet 108 is adapted to direct liquid refrigerant into a chamber 102. The liquid refrigerant flows either continuously or intermittently through the chamber 102 towards an outlet 109. Inside the chamber 102 heat exchange between the liquid refrigerant and electronic equipment 101 takes place. The liquid refrigerant flows out from the chamber 102 through the outlet 109 to a non-shown heat exchanger unit for cooling the refrigerant.

Fig. 7 illustrates a part of a system according to example embodiments of the invention. The arrangement is similar to the disclosure of Fig. 6 as described above with the difference that the electronic equipment 101 is arranged outside the chamber 102. The electronic equipment 101 is arranged in close proximity to the chamber 102, either abutting an outer surface of a wall of the chamber 102 or with a thermal via placed between the electronic equipment and an outer surface of a wall of the chamber 102. In the latter case heat is transferred from the electronic equipment 105 to the chamber 102 and the refrigerant therein by means of the thermal via.

As opposed to a spray of refrigerant, in which the refrigerant forms a mist of small droplets, larger portions of refrigerant may flow through the chamber 102. Liquid refrigerant may flow either continuously or intermittently through the chamber 102. In this case the chamber 102 may be of lesser volume than when spray is used due to the heat exchange between the electronic equipment and the refrigerant primarily taking place in a boundary layer near the electronic equipment. A spray needs a certain volume to spread and absorb heat of the electronic equipment.

When there is a liquid refrigerant flow in a small chamber, flow speed is higher than in a large chamber and thus the heat transfer coefficient is higher with a smaller chamber. A function of the chamber is to form a flow channel for the liquid refrigerant, inside which or adjacent a wall of which the electronic equipment is arranged. The chamber may be provided with undulations on one or more of its inner surfaces to create a turbulent flow of refrigerant inside the chamber, which also increases the heat transfer coefficient. Typically, a heat transfer coefficient for heat transfer from a hot surface (electronic equipment or chamber wall adjacent electronic equipment) to a cooling media (refrigerant) is for liquid water with forced convection (the water being put in motion) about 1500-20000 W/m²K.

Since heat transfer entailing liquid in flowing or sprayed form has high heat transfer coefficient, the system for temperature control can be made more compact than e.g. a prior art system based on cooling and circulating air inside the enclosed space.

When liquid refrigerant flows through the chamber 102 it cools the electronic equipment 101 and in the process is heated, it is primarily intended that the refrigerant remains in liquid phase. It may however happen that the refrigerant evaporates locally in the chamber 102. When a spray of refrigerant is used it is more likely that the refrigerant will evaporate at least partially inside the chamber 102. In both cases the refrigerant will be cooled inside the heat exchanger unit 105 and at the latest return to one homogeneous liquid phase therein.

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. For instance the flow regulating device may comprise a valve to regulate flow of refrigerant. A pump of the flow regulating device may be controlled to provide different refrigerant flows, e.g. by means of pump rotation speed control. The described embodiments are therefore not intended to limit the scope of the invention, which is defined by the appended claims.

Claims

1. A system (100) in a network node (110) for regulating temperature of electronic equipment (101 ) within the network node (110), the system comprising a flow regulating device (104) for circulating a refrigerant, a chamber (102) for receiving the refrigerant from the flow regulating device (104), wherein the chamber (102) has an inlet (108) and an outlet (109), and a heat exchanger unit (105) for exchanging heat with the refrigerant, the heat exchanger unit (105) being connected to the outlet (109) of the chamber (102) and to the flow regulating device (104), wherein the chamber (102) and the electronic equipment (101 ) are arranged such that heat is transferrable between the electronic equipment (101 ) and the refrigerant, when the refrigerant is received by the chamber (102) via the inlet (108).

2. The system (100) according to claim 1 , wherein the electronic equipment (101 ) is enclosed by the chamber (102).

3. The system (100) according to claim 1 , wherein the electronic equipment (101) is located outside the chamber (102).

4. The system (100) according to any one of the preceding claims, further comprising an injecting device (103) arranged at the inlet (108) of the chamber (102) and arranged to inject the refrigerant such that heat is transferrable between the electronic equipment (101 ) and the refrigerant.

5. The system (100) according to any one of the preceding claims, wherein the refrigerant is a liquid suitable for transferring heat between the electronic equipment and the liquid.

6. The system (100) according to any one of claims 4 or 5 when dependent on claim 4, wherein the injecting device (103) is a nozzle.

7. The system (100) according to any one of claims 4 to 6, wherein the injecting device (103) is arranged to spray the refrigerant into the chamber (102).

8. The system (100) according to claim 5, wherein the inlet (108) is arranged to direct the liquid into the chamber to permit the liquid to flow though the chamber (102) in an essentially continuous flow or an intermittent flow.

9. The system (100) according to any one of the preceding claims, wherein the inlet (108) of the chamber (102) is arranged at a same level as or at a higher level than the outlet (109) to allow gravity induced flow of liquid through the chamber (102).

10. The system (100) according to any one of the preceding claims, wherein the heat exchanger unit (105) is arranged for heat exchange between the refrigerant and air.

11. The system (100) according to any one of the preceding claims, wherein the network node (110) comprises an enclosed space (111), in which the electronic equipment (101 ) is arranged, and wherein at least the chamber (102) of the system (100) is arranged inside the enclosed space (111 ) and at least the heat exchanger unit (105) of the system (100) is arranged outside the enclosed space (111).

12. The system (100) according to any one of the preceding claims comprising a refrigerant collection vessel (106) arranged in a part of a refrigerant circuit of the system (100) including the chamber (102), the heat exchanger unit (105) and the flow regulating device (104), wherein the refrigerant collection vessel (106) is adapted to act as a buffer for liquid refrigerant.

13. The system (100) according to any one of the preceding claims, wherein the electronic equipment is configured to handle filtering functions in the radio network node (110).

14. The system (100) according to any one of the preceding claims, further comprising a control unit (111), connected to flow regulating devices for controlling flow of the refrigerant and/or a cooling fluid passing through or over the heat exchanger unit (105), wherein the control unit is arranged and configured to control flow of the refrigerant and/or the cooling fluid based on

- temperature of the electronic equipment, temperature of a wall of the chamber, - temperature of the refrigerant in vapor phase,

- temperature of the refrigerant in liquid phase, temperature of a point at a pipe circuit, wherein the pipe circuit is arranged to connect the flow regulating device, the chamber and the heat exchanger unit, - pressure in a pipe circuit, wherein the pipe circuit is arranged to connect the flow regulating device, the chamber and the heat exchanger unit,

- temperature of the heat exchanger, temperature of the cooling fluid that is to be passed through and/or over the heat exchanger, wherein the heat exchanger is arranged to transfer heat between the cooling fluid and the refrigerant, and a pipe circuit is arranged to connect the flow regulating device, the chamber and the heat exchanger unit, the temperature of the cooling fluid that has passed through and/or over the heat exchanger, wherein the heat exchanger is arranged to transfer heat between the cooling fluid and the refrigerant, and a pipe circuit is arranged to connect the flow regulating device, the chamber and the heat exchanger unit, the temperature of a cooling fluid, being in non-contact with the heat exchanger, wherein the heat exchanger is arranged to transfer heat between the cooling fluid and the refrigerant, and a pipe circuit is arranged to connect the flow regulating device, the chamber and the heat exchanger unit, temperature of any item inside an enclosed space, wherein the radio network node comprises the enclosed space, and wherein the enclosed space comprises the electronic equipment and the system, or temperature of air inside an enclosed space, wherein the radio network node comprises the enclosed space, and wherein the enclosed space comprises the electronic equipment and the system, or a combination thereof.