EP2377379A1

EP2377379A1 - Heat transfer arrangement and electronic housing comprising a heat transfer arrangement and method of controlling heat transfer

Info

Publication number: EP2377379A1
Application number: EP09788464A
Authority: EP
Inventors: Klas Hedberg; Gustaf Wigren
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2009-01-15
Filing date: 2009-01-15
Publication date: 2011-10-19
Also published as: US20110271696A1; WO2010082875A1

Abstract

A heat transfer arrangement comprises a refrigerant circuit (102). The refrigerant circuit (102) comprises an evaporator (104) adapted to be arranged inside an electronic component housing (202), a condenser (108) adapted to be arranged outside the electronic component housing (202), a first conduit leading (106) from the evaporator (104) to the condenser (108), and a second conduit leading from the condenser (108) to the evaporator (104). A refrigerant is present in the refrigerant circuit (102) and in use, under first temperature conditions, is arranged to self-circulate in the refrigerant circuit (102) by evaporating in the evaporator (104), rising as a gas through the first conduit, condensing in the condenser (108) and flowing through the second conduit to the evaporator (104). In the refrigerant circuit (102) a further separate gas or separate gas mixture is present in a quantity such that in use, under second temperature conditions, said quantity of further separate gas or separate gas mixture expands inside the condenser (108) to thereby displace refrigerant from the condenser (108). Heat transfer is thus controlled. Also an electronic component housing comprising such a heat transfer arrangement and a method of controlling heat transfer from such an electronic housing are provided.

Description

HEAT TRANSFER ARRANGEMENT AND ELECTRONIC HOUSING COMPRISING A HEAT TRANSFER ARRANGEMENT AND METHOD OF CONTROLLING HEAT TRANSFER

TECHNICAL FIELD

The present invention relates to a heat transfer arrangement comprising a refrigerant circuit. In use a refrigerant is arranged to self-circulate in the refrigerant circuit. The invention also relates to an electronic component housing comprising such a heat transfer arrangement and a method of controlling heat transfer from such an electronic housing.

BACKGROUND

Heat transfer systems utilizing a refrigerant circulating through an evaporator and a condenser are well known. Such heat transfer systems wherein the refrigerant self- circulates, i.e. gravity and buoyancy are forces driving the circulation of the refrigerant, are sometimes referred to as thermosiphons.

Some electronic component housings need to be cooled due to the heat generated by the electronic components inside the housing. A cooling fan directing air through the housing is sufficient for some applications and/or under certain operating conditions. For other applications and/or under other operating conditions a heat transfer system utilizing a refrigerant, which evaporates in an evaporator and condenses in a condenser, might be required. The evaporator would be arranged to use heat from the electronic components to evaporate the refrigerant and in this way cool the electronic components.

WO99/60709 discloses a method and an apparatus for cooling electronic components of radio base stations installed at elevated locations. An evaporator of a thermosiphon cooling system is in thermal contact with heat-generating electronic components to be cooled. A condenser of the thermosiphon cooling system is arranged above the evaporator. The condenser is constructed and arranged for natural convection of ambient air. Generally, a modern radio communication system 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 comprises an electronic component housing. Inside the electronic component housing there are arranged electronic components and circuitry 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.

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 impair 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 and a thermosiphon cooling system as disclosed in WO99/60709, mentioned above, could be used to cool the electronic component housing. WO99/60709 does however not disclose how cooling may be controlled in a thermosiphon cooling system. Under certain conditions it is namely desirable to not cool the electronic component housing in order to avoid a too low temperature inside the electronic component housing, which also could harm the electronic components and circuitry inside the electronic component housing.

SUMMARY An object of the present invention is to obviate the above disadvantage and provide an improved heat transfer arrangement with a refrigerant arranged to self-circulate. According to an aspect of the invention, the object is achieved by a heat transfer arrangement comprising a refrigerant circuit. The refrigerant circuit comprises an evaporator adapted to be arranged inside an electronic component housing, a condenser adapted to be arranged outside the electronic component housing, a first conduit leading from the evaporator to the condenser, and a second conduit leading from the condenser to the evaporator. A refrigerant is present in the refrigerant circuit and in use, under first temperature conditions, is arranged to self-circulate in the refrigerant circuit by evaporating in the evaporator, rising as a gas through the first conduit, condensing in the condenser and flowing through the second conduit to the evaporator. In the refrigerant circuit a further separate gas or separate gas mixture is present in a quantity such that in use, under second temperature conditions, said quantity of further separate gas or separate gas mixture expands inside the condenser to thereby displace refrigerant from the condenser.

It is to be understood that the further separate gas or separate gas mixture remains separate from the refrigerant. That is, the further separate gas or separate gas mixture may be mixed with the refrigerant in the refrigerant circuit but it will remain, under intended operating conditions, a separate gas or separate gas mixture different from the refrigerant.

A prevailing pressure inside the refrigerant circuit is primarily determined by the pressure of gas inside the refrigerant circuit because a liquid, i.e. in this case liquid refrigerant, is incompressible. The pressure inside the refrigerant circuit is dependent on refrigerant saturation pressure at prevailing temperature. When temperature is high inside and/or outside the electronic component housing, the pressure inside the refrigerant circuit is high due to high refrigerant saturation pressure. As temperature decreases, inside and/or outside the electronic component housing, the pressure inside the refrigerant circuit decreases due to a lower refrigerant saturation pressure. Thus, under the first temperature conditions the temperature inside and/or outside the electronic component housing is generally higher than under the second temperature conditions.

At reduced gas pressure inside the refrigerant circuit, the further separate gas or separate gas mixture will expand in comparison with refrigerant in gas form. The refrigerant in gas form will thus be displaced from the condenser and an inner heat transfer surface thereof. Heat transfer in the condenser is reduced and thus also the heat transferred from the electronic component housing.

As a result, the above mentioned object is achieved.

At further reduced gas pressure inside the refrigerant circuit most of the refrigerant in gas form will have been displaced from the inner heat transfer surface of the condenser by the separate gas or separate gas mixture and heat transfer is reduced to a minimum.

In example embodiments of the heat transfer arrangement, a constant weight of the refrigerant and a constant weight of the further separate gas or separate gas mixture may be present in the refrigerant circuit. A heat transfer arrangement with an uncomplicated refrigerant circuit can be used. There is no need for any additional devices for actively adding or removing the refrigerant and/or the further separate gas or separate gas mixture from the refrigerant circuit to control heat transfer.

In example embodiments of the heat transfer arrangement, the further separate gas or separate gas mixture may be present in the refrigerant circuit at a fixed weight ratio with respect to the refrigerant. Again, a heat transfer arrangement with an uncomplicated refrigerant circuit can be used and there is no need for any additional devices for adding or removing the refrigerant and/or the further separate gas or separate gas mixture from the refrigerant circuit to control heat transfer.

In example embodiments the refrigerant circuit may be defined as comprising only components flowed through by refrigerant during the self-circulation of refrigerant.

According to example embodiments the weight ratio of the further separate gas or gas mixture may be in the interval of 3% - 40% of the refrigerant.

According to example embodiments the weight ratio of the further separate gas or gas mixture may be in the interval of 5% - 25% of the refrigerant. In example embodiments the refrigerant may have a molecular structure referred to as R134a. R 134a is a refrigerant having suitable properties and will operate in temperature intervals commonly occurring for electronic component housings. Other refrigerants may also be suitable, as well as e.g. water, methanol or acetone.

In example embodiments the separate gas may be nitrogen or the separate gas mixture may be air. Nitrogen and air are readily available and will remain separate from the refrigerant in the refrigerant circuit.

In example embodiments of the heat transfer arrangement, the condenser and/or the evaporator may be arranged at an angle of 5 - 60 degrees from a horizontal line. In this way vertical installation height of the heat transfer arrangement may be reduced while still a respective external heat transfer surface of the evaporator and/or the condenser may be available for lateral exposure.

According to example embodiments the condenser and/or the evaporator may be of plate and fin type.

In an aspect of the invention an electronic component housing may comprise a heat transfer arrangement as discussed above. According to example embodiments it may further comprise a first gas moving device for circulating a gas such as air inside the electronic component housing over an outer surface area of the evaporator. In this way cold gas may be transported from the evaporator to electronic components and warm gas from the electronic components to the evaporator.

According to example embodiments the electronic component housing may comprise a second gas moving device for blowing ambient air over an outer surface area of the condenser. Heat transfer between ambient air and the condenser may be improved by mechanically transporting air over the outer heat transfer surface.

According to example embodiments the electronic component housing may comprise two of the above mentioned heat transfer arrangements, the evaporators of which are arranged adjacent to each other inside the electronic component housing. Cooling effect may in this way be increased inside the electronic housing while space requirement for a collective heat transfer arrangement is kept low inside the electronic housing.

According to example embodiments the electronic component housing may be part of a radio base station.

In an aspect of the invention a method of controlling heat transfer from an electronic component housing, e.g. as mentioned above, to an environment, may comprise the steps of: - Self-circulating the refrigerant in the refrigerant circuit, under first temperature conditions, by evaporating in the evaporator, rising as a gas through the first conduit, condensing in the condenser and flowing through the second conduit to the evaporator.

- Controlling the second gas moving device.

- Stopping the second gas moving device when heat transfer is to be reduced, and - displacing the refrigerant from the condenser, under second temperature conditions, when a pressure inside the refrigerant circuit is reduced and the separate gas or separate gas mixture expands inside the condenser.

In example embodiments a step of controlling the first gas moving device to circulate a gas inside the electronic component housing over the outer surface area of the evaporator, may be included.

In example embodiments the step of controlling the first gas moving device may include: Reducing a speed of the first gas moving device to a minimum speed when a limit temperature in the interval of +5 to +30 degrees Celsius inside the electronic component housing is reached, and maintaining the minimum speed when a temperature inside the electronic component housing is lower than the limit temperature. In this way a minimum circulation of gas inside the electronic component housing is ensured.

In example embodiments the step of stopping the second gas moving device may be performed when a temperature inside the electronic component housing is in the interval of +5 to +20 degrees Celsius and the second gas moving device is maintained stopped at even lower temperatures inside the electronic component housing. Heat exchange between the condenser and the environment will in this way be reduced and thus also heat transferred from inside the electronic component housing to the environment. Thus, the heat transfer arrangement will contribute less to further cooling of the electronic component housing and favourable temperature conditions may more easily be maintained inside the electronic component housing.

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 illustrates schematically a heat transfer arrangement according to example embodiments, Fig. 2 illustrates schematically an electronic component housing according to example embodiments comprising a heat transfer arrangement,

Fig. 3 illustrates schematically an electronic component housing according to example embodiments comprising two heat transfer arrangements, and

Fig. 4 illustrates an exemplary method for controlling heat transfer from an electronic housing.

DETAILED DESCRIPTION

The present invention now will be described more fully with reference to the accompanying drawings, in which example embodiments are shown. However, this invention should not be construed as limited to the embodiments set forth herein.

Disclosed features of example embodiments may be combined as readily understood by one of ordinary skill in the art to which this invention belongs. Like numbers refer to like elements throughout.

As used herein, the term "comprising" or "comprises" is open-ended, and includes one or more stated features, elements, steps, components or functions but does not preclude the presence or addition of one or more other features, elements, steps, components, functions or groups thereof.

As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

As used herein, the common abbreviation "e.g.", which derives from the Latin phrase "exempli gratia," may be used to introduce or specify a general example or examples of a previously mentioned item, and is not intended to be limiting of such item. If used herein, the common abbreviation "i.e.", which derives from the Latin phrase "id est," may be used to specify a particular item from a more general recitation.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

It will be understood that when an element is referred to as being "coupled" or

"connected" to another element, it can be directly coupled or connected to the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly coupled" or "directly connected" to another element, there are no intervening elements present.

Well-known functions or constructions may not be described in detail for brevity and/or clarity.

Fig. 1 illustrates schematically a heat transfer arrangement according to example embodiments. A refrigerant circuit 102 comprises an evaporator 104, a first conduit 106, a condenser 108 and a second conduit 110. Inside the refrigerant circuit 102 there is a refrigerant and a further separate gas or further separate gas mixture. The refrigerant in liquid form inside the evaporator 104 evaporates and rises in gas form through the first conduit 106 to the condenser 108. Inside the condenser 108 the refrigerant in gas form condenses to liquid and flows through the second conduit 110 back to the evaporator 104. In this manner the refrigerant self-circulates in the refrigerant circuit 102.

Gravity and buoyancy are forces driving the self-circulation. When the condenser 108 is arranged above the evaporator 104, as schematically shown, an efficient self-circulation of refrigerant takes place. Liquid refrigerant will not be collected to any substantial extent in the condenser 108 but will flow through the second conduit 110 down to the evaporator 104. Also in a refrigerant circuit with the evaporator and the condenser arranged laterally beside each other and the first conduit arranged such that refrigerant in gas form can rise therein, a refrigerant may self-circulate. However, in this case liquid refrigerant would take up part of the condenser, the condenser and evaporator being communicating vessels.

Fig. 2 illustrates schematically an electronic component housing according to example embodiments comprising a heat transfer arrangement. The electronic component housing 202 is adapted to house electronic components 204. In example embodiments the electric component housing 202 may be a radio base station and the electric components 204 may be part of devices associated with such a radio base station, e.g. a radio unit. The heat transfer arrangement is adapted to cool the electronic components 204 and comprises a refrigerant circuit 102. An evaporator 104 of the refrigerant circuit 102 is arranged inside the electric component housing 202. Further in the refrigerant circuit 102 a first conduit 106 leads from the evaporator 104 to a condenser 108 arranged outside the electronic component housing 202. From the condenser 108 a second conduit 110 leads back to the evaporator 104. The refrigerant circuit is filled with a refrigerant and a further separate gas or further separate gas mixture. The refrigerant self-circulates inside the refrigerant circuit 102.

Inside the electronic component housing 202 a first gas moving device, e.g. a first fan 206, is arranged and adapted to circulate a gas, commonly air, inside the electronic component housing 202. Outside the electronic component housing 202 a second gas moving device, e.g. a second fan 208, is arranged and adapted to blow ambient air over an outer surface area of the condenser 108. The condenser 108 and also the second fan 208 may be arranged in a non-shown separate housing. Suitably such a separate housing communicates with ambient environment. To save vertical space inside the electronic component housing the evaporator 104 may be arranged at an acute angle α from a horizontal line, e.g. 5 - 60 degrees. Also the condenser 108 may arranged at an acute angle, the same as α or different from α.

In use, the electronic components 204 inside the electronic component housing 202 generate heat. Depending inter alia on generated heat, construction of the electronic component housing 202 and on ambient conditions such as temperature, air movement (e.g. wind) and precipitation (e.g. rain), the temperature inside the electronic component housing 202 may increase to a level which could harm the electronic components 204. The heat transfer arrangement and primarily the evaporator 104 of the refrigerant circuit 102 is arranged to cool the inside air of the electronic component housing 202 to avoid such harmful temperature levels. A suitable aim of example embodiments may be to keep the temperature inside the electronic component housing 202 below +60 degrees Celsius.

Under certain conditions the refrigerant self-circulates inside the refrigerant circuit 102 as explained above with reference to Fig. 1. By utilizing heat inside the electronic component housing 202 for evaporating the refrigerant, the temperature of the air inside the electronic component housing 202 will fall and may be used to cool the electronic components 204. Inter alia to ensure proper cooling of the electronic components 204, the first fan 206 may circulate the air, as indicated by arrow 210, inside the electronic component housing 202 past the evaporator 104 and the electronic components 204. Circulation in another direction than indicated by arrow 210 is also possible. In the condenser 108 the refrigerant in gas form will condense to liquid form by emitting heat to the ambient environment. Transfer of heat from the condenser 108 to the ambient environment may be increased by switching on the second fan 208 to blow ambient air over an outer surface area of the condenser 108, e.g. in the direction indicated by arrow 212.

To avoid harming the electronic components 204, it is also desirable to not allow the temperature inside the electronic component housing 202 to fall below a certain temperature. A suitable aim of example embodiments may be to keep the temperature inside the electronic component housing 202 above +5 degrees Celsius.

Fig. 3 illustrates schematically an electronic component housing according to example embodiments. There are two heat transfer arrangements, each comprising a separate refrigerant circuit 102, 102', associated with the electronic component housing 202. Evaporators 104, 104' of the refrigerant circuits 102, 102' are arranged adjacent each other inside the electronic component housing 202. A circulating gas inside the electric component housing 202 will be cooled in two steps as it flows first over an outer surface of one evaporator 104 and then over an outer surface of the other evaporator 104'. By this arrangement a higher temperature efficiency is achieved and the circulating gas inside the electronic component housing 202 will be cooled to a lower temperature than if only one refrigerant circuit would be used. The gas inside the electronic component housing 202 may be circulated in any direction but the direction indicated by arrow 302 is advantageous when condensers 108, 108', of the refrigerant circuits 102, 102' are arranged as shown in Fig. 3 and ambient air is blown as indicated by arrow 304.

With reference to Fig. 4 an exemplary method for controlling heat transfer from an electronic component housing is described. The electronic component housing may for instance be a radio base station, from which heat is to be transferred to an ambient environment. Ambient conditions and conditions inside an electronic component housing are such that a refrigerant self-circulates 402 inside a refrigerant circuit of a heat transfer arrangement for transferring heat from the electronic component housing to the environment. A fan adapted to blow ambient air over a condenser of the refrigerant circuit is controlled 404, e.g. speed controlled. Temperature inside the electronic component housing is monitored 406. If the temperature is above a limit value, e.g. +10 degrees Celsius, control of the second fan continues. If the temperature is below the limit value, the second fan is stopped 408 and heat transfer from the electronic component housing reduced. As ambient temperature decreases, self-circulation in the refrigerant circuit decreases further 410 due to the separate gas or separate gas mixture displacing refrigerant in gas form from an inner heat exchange surface of the condenser and heat exchange from the electronic component housing to the environment by means of the heat transfer arrangement is reduced to a minimum. The temperature limit value inside the electronic component housing may suitably be selected within the interval +5 to +20 degrees Celsius.

According to example embodiments, inside a refrigerant circuit of a heat transfer arrangement there is a refrigerant and a further separate gas or further separate gas mixture. The refrigerant may be R134a and the separate gas may be nitrogen. Alternatively, a separate gas mixture to be used may be air. R 134a is a name for 1 ,1,1 ,2- Tetrafluoroethane, it has the formula CH₂FCF₃ The refrigerant and the separate gas or separate gas mixture are present at a fixed weight ratio inside the refrigerant circuit, i.e. the refrigerant circuit, during manufacturing, is filled with a predetermined quantity of refrigerant and a predetermined quantity of the separate gas or separate gas mixture and then sealed. Once ready for installation, e.g. in an electronic component housing, the refrigerant circuit contents remain unaltered.

Having a refrigerant and a separate gas or separate gas mixture inside the refrigerant circuit will give the refrigerant circuit a different characteristic compared to if the refrigerant circuit would be filled will refrigerant only. With the separate gas or separate gas mixture, the cooling capacity of the refrigerant circuit will depend on temperature: The cooling capacity is high when the temperature is high and the cooling capacity is low when the temperature is low. At a fixed weight ratio of 3 - 40% of separate gas or separate gas mixture an advantageous characteristic is achieved, in particular for heat transfer arrangements for electronic component housings, e.g. radio base stations. A weight ratio interval of further interest would be separate gas or separate gas mixture at 5 - 25%.

Utilizing a heat transfer arrangement with a refrigerant circuit where the refrigerant and the separate gas or separate gas mixture weight ratio is within these intervals, the temperature inside an electronic component housing may be kept within favourable limits. In combination with gas moving devices, such as the above exemplified first and second fans, the temperature inside an electronic component housing is easily controlled.

The volume ratio between refrigerant in gas form and the separate gas or separate gas mixture inside the refrigerant circuit is dependent on the pressure inside the refrigerant circuit, which in turn depends on the temperature inside the electronic component housing and the ambient temperature.

The refrigerant exists inside the refrigerant circuit in both liquid form and gas form. The separate gas or separate gas mixture only exists in gas form inside the refrigerant circuit. A high pressure inside the refrigerant circuit depends on more refrigerant being in gas form than at a low pressure. The higher the pressure inside the refrigerant circuit, the less volume the separate gas or separate gas mixture will occupy inside the refrigerant circuit. Conversely, as pressure is reduced inside the refrigerant circuit, the separate gas or separate gas mixture expands in comparison with refrigerant in gas form. Since the separate gas or separate gas mixture is lighter than liquid refrigerant the separate gas or separate gas mixture will expand inside the condenser and displace refrigerant in gas form from the condenser and an inner heat transfer surface thereof.

The gas, e.g. air, inside the electronic component housing is circulated by the first fan, over the outer surface area of the evaporator and towards the electronic components. The speed of the first fan may suitably be controlled. Even though the first fan could be stopped at low temperatures inside the electronic component housing, it is suitable to maintain a minimum speed of the first fan e.g. to avoid local heat build up at electronic components.

In a first situation, when electronic components inside the electronic component housing generate heat to such an extent that the inside of the electronic component housing requires cooling, the refrigerant self-circulates in the refrigerant circuit and the second fan is controlled to blow air over the outer surface of the condenser to improve heat transfer from the condenser to the environment.

In a second situation, e.g. when ambient temperature has fallen, a desired temperature may be maintained inside the electronic component housing by means of the heat transfer arrangement but without the aid of the second fan. The second fan is stopped to decrease the heat transfer between the condenser and the environment. The refrigerant still self-circulates in this situation and a desired temperature is maintained inside the electronic component housing.

An additional or separate criterion for stopping the second fan may be when a temperature inside the electronic component housing is in the interval of +5 to +20 degrees Celsius.

In a third situation, e.g. when ambient temperature has fallen further, a desired temperature may be maintained inside the electronic component housing without the aid of the heat transfer arrangement, heat transfer from the electronic component housing to the environment is reduced to a minimum due to the separate gas or separate gas mixture having expanded to such an extent inside the condenser that self-circulation of the refrigerant has been reduced to a minimum.

Example embodiments may be combined as understood by a person skilled in the art. It is also understood by those skilled in the art that first and second fans may be any other gas moving devices suitable for producing a flow of gas over an outer surface of an evaporator or condenser. A heating apparatus may be arranged to heat the inside of the electronic component housing to avoid too low temperatures inside the electronic component housing even when the heat transfer from the electronic component housing is minimal. Heating could become necessary under certain ambient conditions.

Therefore, it is to be understood that the foregoing is illustrative of various example embodiments and is not to be limited to the specific embodiments disclosed and that modifications to the disclosed embodiments, combinations of features of disclosed embodiments as well as other embodiments are intended to be included within the scope of the appended claims.

Claims

1. A heat transfer arrangement comprising a refrigerant circuit (102; 102'), which refrigerant circuit (102; 102') comprises

- an evaporator (104; 104') adapted to be arranged inside an electronic component housing (202),

- a condenser (108; 108') adapted to be arranged outside the electronic component housing (202),

- a first conduit leading (106) from the evaporator (104; 104') to the condenser (108; 108'), and - a second conduit leading (110) from the condenser (108; 108') to the evaporator

(104; 104"), wherein a refrigerant is present in the refrigerant circuit (102; 102') and in use, under first temperature conditions, is arranged to self-circulate in the refrigerant circuit (102;

102') by evaporating in the evaporator (104; 104"), rising as a gas through the first conduit, condensing in the condenser (108; 108') and flowing through the second conduit to the evaporator (104; 104') characterized in that in the refrigerant circuit (102; 102') a further separate gas or separate gas mixture is present in a quantity such that in use, under second temperature conditions, said quantity of further separate gas or separate gas mixture expands inside the condenser (108; 108') to thereby displace refrigerant from the condenser(108; 108').

2. The heat transfer arrangement according to claim 1 , wherein a constant weight of the refrigerant and a constant weight of the further separate gas or separate gas mixture are present in the refrigerant circuit (102; 102').

3. The heat transfer arrangement according to any one of claims 1 and 2, wherein the further separate gas or separate gas mixture is present in the refrigerant circuit (102; 102') at a fixed weight ratio with respect to the refrigerant.

4. The heat transfer arrangement according to claim 3, wherein the weight ratio of the further separate gas or gas mixture is in the interval of 3% - 40% of the refrigerant.

5. The heat transfer arrangement according to claim 4, wherein the weight ratio of the further separate gas or gas mixture is in the interval of 5% - 25% of the refrigerant.

6. The heat transfer arrangement according to any one of the preceding claims, wherein the refrigerant has a molecular structure referred to as R134a.

7. The heat transfer arrangement according to any one of the preceding claims, wherein the separate gas is nitrogen or the separate gas mixture is air.

8. The heat transfer arrangement according to any one of the preceding claims, wherein a an outer heat transfer surface of the condenser (108; 108') and/or the evaporator (104; 104') is/are arranged at an angle (α) of 5 - 60 degrees from a horizontal line.

9. An electronic component housing comprising a heat transfer arrangement according to any one of claims 1 - 8 and further comprising a first gas moving device (206) for circulating a gas such as air inside the electronic component housing (202) over an outer surface area of the evaporator (104; 104').

10. The electronic component housing according to claim 9, comprising a second gas moving device (208) for blowing ambient air over an outer surface area of the condenser (108; 108').

11. The electronic component housing according to any one of claims 9 -10, wherein the electronic component housing (202) is part of a radio base station.

12. A method of controlling heat transfer from an electronic component housing according to any one of claims 9 - 11 to an environment, comprises the steps of - self-circulating (402) the refrigerant in the refrigerant circuit, under first temperature conditions, by evaporating in the evaporator, rising as a gas through the first conduit, condensing in the condenser and flowing through the second conduit to the evaporator, - controlling (404) the second gas moving device,

- stopping (408) the second gas moving device when heat transfer is to be reduced and,

- displacing the refrigerant from the condenser, under second temperature conditions, when a pressure inside the refrigerant circuit is reduced and the separate gas or separate gas mixture expands inside the condenser.

13. The method of controlling heat transfer according to claim 12, comprising a step of

- controlling the first gas moving device to circulate a gas inside the electronic component housing over the outer surface area of the evaporator.

14. The method of controlling heat transfer according to claim 13, wherein the step of controlling the first gas moving device includes,

- reducing a speed of the first gas moving device to a minimum speed when a limit temperature, in the interval of +5 to +30 degrees Celsius, inside the electronic component housing is reached, and

- maintaining the minimum speed when a temperature inside the electronic component housing is lower than the limit temperature.

15. The method of controlling heat transfer according to any one of claims 12 - 14, wherein the step of stopping (408) the second gas moving device is performed when a temperature inside the electronic component housing is in the interval of +5 to +20 degrees Celsius and the second gas moving device is maintained stopped at even lower temperatures inside the electronic component housing.