WO2010027311A1

WO2010027311A1 - A cooling system for electronic devices and a cabinet including such a system

Info

Publication number: WO2010027311A1
Application number: PCT/SE2008/051002
Authority: WO
Inventors: Per Engblom
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2008-09-08
Filing date: 2008-09-08
Publication date: 2010-03-11

Abstract

The present invention relates to a cooling system (2) for electronic devices (11) installed in a confined space, which cooling system comprises a closed pipe thermosiphon system. The evaporator (3) comprises of a plurality of elongate bars (6) adapted to be arranged in recesses (15) in said electronic devices (11), wherein the elongate bars (6) include an incoming inner passage (8), which is connected to the condenser (4) via the first connection pipe (12), and an outgoing outer passage (9), which is connected to the condenser (4) via the second connection pipe (13), and which is arranged to be in thermal contact with the recesses (15) of the electronic devices (11) such that the heat generated by the electronic devices (11) causes the refrigerant to evaporate as it passes through the outer passage (9) such that the electronic devices (11) are cooled from the said recesses. The condenser (4) is cooled by forced ventilation. The invention also relates to a cabinet and an electronic device.

Description

A COOLING SYSTEM FOR ELECTRONIC DEVICES AND A CABINET INCLUDING SUCH A SYSTEM

TECHNICAL FIELD

The present invention relates generally to the field of mobile communications, and, more particularly to a cooling system for electronic devices. The invention also relates to a cabinet including such a cooling system.

BACKGROUND

Most types of electric devices, such as e.g. radio units, power units, amplifiers and the like, produce heat and are in need of cooling in order to work properly and in order not to overheat. Conventionally, this cooling is performed by air cooling, and in most cases a fan is used to distribute cold or ambient air towards the heat generating electric equipment in order to lead away part of the generated heat. In radio applications, such as base stations and the like, the necessity of cooling is sometimes very high, since several heat generating electronic devices are located in close vicinity, generating a lot of heat inside a confined volume, such as e.g. a cabinet or a common housing.

In order to solve the heating in such cases, the electronic devices either need to be separated by a certain gap, or to include a finned portion, in order to allow cooling of all units. Additionally, several fans need to be utilized to create the necessary air flow, and for best performance the air needs to be guided such that all heat generating parts of the electronic devices are affected by the cooling air. All these constructional details added together result in rather bulky cabinets, in which a good amount of the space is taken up by air, air ducts, and fans. The fans in themselves create additional problems. Firstly, they create a lot of noise, such that they call for expensive (and bulky) sound absorbing ducts or similar. In addition, they contribute to an important part of the energy consumption of the electronic device aggregate.

Thus, there is a need for a an alternative type of cooling system.

One such alternative cooling system is known from WO 99/60709, which discloses a method and an apparatus for cooling heat-generating components of radio base stations. A thermosiphone cooling system is used for cooling the heated components, and a condenser is constructed and mounted for natural convection of air through it, at a summit portion of the pipe circuit outside and above the radio base station. This solution solves the problem of cooling radio base stations that are located outside. It is however not adaptable to electronic devices that are located inside a confined space. Two major differences that makes the described cooling system hard to use in such conditions is that the need for cooling is generally substantially greater, and that it is not possible to use natural convection to cool the condensers, since they are located inside, in non windy conditions, and since a massive cooling effect is generally needed. Also, since the cooling system proposed in WO 99/60709 is located outside it is not, in contrast to electronic devices that are located inside a confined space, dimensionally restricted.

Thus, there is a need for a cooling system which is highly efficient, not bulky, adaptable to conventional electronic devices, and not dependent on natural convection for cooling.

SUMMARY

An object of the invention is to overcome at least on of the above mentioned drawbacks of the prior art.

According to a first aspect, the invention relates to a cooling system for electronic devices installed in a confined space, which cooling system comprises a closed pipe circuit, containing a refrigerant, wherein the closed pipe circuit comprises: an evaporator, for evaporating the refrigerant when subjected to heat generated by the electronic devices and thereby cooling the electronic devices; a condenser, for condensing the thus evaporated refrigerant; and a first and second connection pipe for connecting the evaporator and the condenser, wherein the condenser is arranged above the evaporator, such that the heavier condensed refrigerant strives downwards through the first connection pipe towards the evaporator, and the lighter evaporated refrigerant strives upwards through the second connection pipe towards the condenser thus forming a self-circulating cooling system. The evaporator comprises a plurality of elongate bars adapted to be arranged in recesses in said electronic devices, wherein the elongate bars include an incoming inner passage, which is connected to the condenser via the first connection pipe, and an outgoing outer passage, which is connected to the condenser via the second connection pipe, and which is arranged to be in thermal contact with the recesses of the electronic devices such that the heat generated by the electronic devices causes the refrigerant to evaporate as it passes through the outer passage such that the electronic devices are cooled from the said recesses. The condenser is cooled by forced ventilation.

The solution according to the invention yields that effective cooling of electronic devices inside a confined space may be achieved. With respect to prior art the cooling system according to the invention is both more effective and more compact. Also, a cabinet including such a cooling system will be both more compact and lighter, since the relatively heavy air duct structure may be omitted.

Preferably the condenser is cooled by at least one fan.

According to one embodiment the elongate bars are adapted to be arranged such that substantially the whole outer surface of the elongate bars is in thermal contact with electronic devices. Preferably, the elongate bars are adapted to be arranged in through holes in said electronic devices such that substantially the whole outer surface of the elongate bars is in thermal contact with the interior of a electronic device.

According to another embodiment the elongate bars comprise connecting means for connecting them to fixing means in order to fix the electronic device to the corresponding elongate bar, wherein the elongate bars are arranged to be inserted horizontally from one side of the electronic devices, and the fixing means are arranged to be fixed from the opposite side. Preferably, the elongate bars are arranged to be inserted from a rear side of an electronic device and the fixing means are arranged to be fixed from a front side.

Advantageously, the plurality of elongate bars are arranged at several levels, at specific distances D from each other, which distances D correspond to the height of electronic device modules to be cooled by the cooling system, such that a modular system of electronic devices may be arranged, such that they are cooled by said cooling system, and individually replaceable from said modular system.

The cooling system according to the invention provides a system, which is efficient, which may be placed in a confined space, which is not dependent on wind, and which consumes less energy than conventional cooling systems.

The invention also relates to a cabinet including a cooling system as described above. Preferably, the cabinet is divided into two separate parts, a upper part including the condenser and a lower part including the evaporators and the electronic devices to be cooled, and wherein these parts are separated by an air tight partition such that the air for cooling the condensers is kept out from said lower part.

Also, air inlets and air outlets may be arranged in the upper part for conveying ambient cooling air passed the condenser and preferably a fan is arranged inside said upper part.

Still other objects and advantages of the present invention will become apparent from the following detailed description in conjunction with the accompanying drawings, attention to be called to the fact, however, that the following drawings are illustrative only, and that various modifications and changes may be made to the specific embodiments within the scope of the appended claims. It should further be understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a front view of a cabinet in which the cooling system according to the invention is installed;

Figure 2 is a cross sectional view of the cabinet in fig. 1, cut along the line 2-2;

Figure 3 is a perspective view of the cooling system according to the invention;

Figure 4 is a front view of the cooling system in fig. 3;

Figure 5 is a cross sectional view of the cooling system in fig. 4, cut along the line 5-5;

Figure 6 shows a cross section of an electronic device with the cooling system according to the invention;

Figure 7 shows an enlargement of a detail in fig. 6;

Figure 8 is a perspective view of an electronic device with the cooling system according to the invention; and Figure 9 is an exploded view of an electronic device and a cooling system according to the invention.

DETAILED DESCRIPTION

In the following the invention will be described with reference to the embodiment shown in the figures. Generally the invention relates to a cooling system for electronic devices, such as radio units, power supply units, filter units etc.

The cooling system according to the invention functions as a thermosiphon, which refers to a method of heat exchange through a phase change heat pump that depends on gravity. It allows the cooling and heating of objects by changing the phase of a liquid inside a closed system that relies on the principles of convection and gravity to move the fluid through the system.

Figure 1 is a front view of an open cabinet 1, in which a cooling system according to the invention is installed, and figure 2 is a cross sectional view from which it is clear how the cooling systems 2 is arranged inside the cabinet 1 , m order to cool electronic devices 11 Generally the cooling system 2 includes a closed pipe circuit, containing a refrigerant. The closed pipe circuit comprises a thermal collector m form of an evaporator 3, for evaporating the refrigerant when subjected to heat generated by an electronic device 11, such that the electronic device 11 is cooled. It also comprises a condenser 4, for condensing the thus evaporated refrigerant. The condenser is preferably cooled by forced ventilation and more preferably by means of at least one fan 5.

In the embodiment shown in fig 2, the cooling system and the electronic devices are located in a confined space, e g a cabinet 1 A partition wall 16 is arranged to separate the interior of the cabinet 1 in two main parts such that air for cooling the condensers is kept out from the lower part, such that dust or the like is kept out of the lower part.

In the upper part the condenser 4 and the fans 5 are located, and in the lower part the evaporator 3 and the radio units 11 are located.

The upper part of the cabinet 1 comprises ventilation openings 5a and 5b, upstream and downstream, respectively, of the fans 5 The lower part, on the other hand is preferably tightly sealed m order to avoid that dust or the like that may affect the function of the electronic devices enters this part of the cabinet. However, as an additional cooling, the lower part of the cooling system 2 may include additional evaporators (not shown), which are arranged such that air may be circulated in a closed system past the electronic devices and these additional evaporators. Preferably, a fan is arranged to circulate air. The additional evaporators are an optional part of the cooling system and thus contain the same refrigerant as the rest of the system. Preferably the additional evaporators are provided with external fins in order to maximise the heat exchange with the passing air.

From figures 3-5 it is apparent that the evaporator 3 comprises of a plurality of elongate bars 6, which in the shown embodiment are represented by tubular bars with a circular cross section. The elongate bars 6 are adapted to be arranged in recesses 15 of corresponding dimensions and quantity in the electronic devices 11. In the shown embodiment the recesses 15 are constituted by through holes through the electronic devices, which offer optimal heat absorption from the electronic device. However, since the electronic devices are adapted to be placed in close contact to each other it is also feasible to adapt the form of the elongate bars to outer recesses of the electronic devices or to any types of cavities in the electronic devices. For optimal heat transfer and irrespective of the specific shapes, it is however desired that the precision between the form of elongate bars 6 and the recesses 15 is sufficiently good to avoid heat transfer inhibiting gaps.

The circular cross section of the elongate bars 6 is a compromise between, on the one side, optimal heat transfer, and on the other side manufacturing costs. For optimal heat transfer the surface contact should be maximised, such as e.g. in a star-formed cross-section. For optimal manufacturing costs a circular cross-section is perfect. Further, circular cross-section provides an optimal pressure tolerance, and in this case, the heat transfer of a circular bar is more than sufficient.

In the shown embodiment the condenser 4 includes two condenser plates 7a and 7b, placed one over the other. Condensers are however well known to a person skilled in the art of cooling, and may be designed in many different ways that are all obvious to the skilled person.

In figure 6, a first connection pipe 12 and a second connection pipe 13 are shown. These connection pipes 12 and 13 are arranged for connecting the evaporator 3 to the condenser 4, wherein the condenser 4 is arranged above the evaporator 3, such that the heavier condensed refrigerant strives downwards through the first connection pipe 12 towards the evaporator 3, and the lighter evaporated refrigerant strives upwards through the second connection pipe 13 towards the condenser 4, thus forming a self-circulating cooling system.

In the shown embodiment the cross section of the second connection pipe 13 is greater than the cross section of the first connection pipe 12. This is advantageous since liquid is transported in the first connection pipe 12, wherein gas and vapour, which is of course more voluminous than liquid, is arranged to be transported in the second connection pipe 13.

From fig. 6 it is also evident that the elongate bars 6 include an incoming inner passage 8, which is connected to the condenser 4 via the first connection pipe 12, and an outgoing outer passage 9, which is connected to the condenser 4 via the second connection pipe 13, and which is arranged to be in thermal contact with the recesses 15 of the electronic devices 11 such that the heat generated by the electronic devices causes the refrigerant to evaporate as it passes through the outer passage 9 such that the electronic devices 11 are cooled from the inside.

Preferably, the whole cooling system is made of a thermally conductive material, such as a light metal or any other material of similar properties. A preferred light metal is Aluminium since it also has the advantage of being light, ductile and elastic, and thereby possesses a very good combination of properties for the purpose. Normally, the main heating of the refrigerant occur inside the outer passage, such that the energy needed for evaporating the refrigerant (i.e. boiling enthalpy) is taken directly from the insides of the electronic devices, which are thus effectively cooled. The boiling of the refrigerant inside the outer passage is also helped by that the outer passage is larger that the inner passage, such that the increase in volume that is implied by the change in phase is allowed.

Preferably, details of the electronic devices that generate a lot of heat may be arranged close to the recesses 15, to lead away the generated heat as efficient as possible. Moreover the electronic device may include a solid internal part. If so, the recess may be arranged as holes in this solid part, such that this solid part is cooled. Also, in order to optimise the conductivity between the elongate bars and the electronic device, a heat conductive paste or the like may be provided to fill gaps that might be formed between the bars and the inside walls of the recesses, which gaps otherwise might worsen the conductivity substantially. In the illustrated embodiment, the recesses 15 are constituted by through holes, which pass right through the electronic devices. The elongate bars 6 are inserted into these through holes.

Inside the elongate bars, the refrigerant flows as illustrated by the arrows in fig. 7, i.e. inwards through the inner passage 8, which is defined by a tubular wall 8a. The inner end 8b of the inner passage 8 is open such that the refrigerant may pass from the inner passage 8 to the outer passage 9. The outer passage 9 and the inner passage 8 are coaxial with each other and arranged such that the refrigerant flows in a first direction through the inner passage 8 and the flows back in the opposite direction through the outer passage 9.

Further, the elongate bars 6 comprise connecting means 9a, such as e.g. external threads, for connecting them to fixing means 10 in order to firmly fix the electronic device 11 to the corresponding elongate bar 6. The elongate bars are arranged to be inserted horizontally from one side of the electronic devices, preferably the rear side of the electronic devices 11, and the fixing means 10 are arranged to be fixed from the opposite side, i.e. preferably the front side. Such an arrangement is convenient since it allows for an individual electronic device to be replaced easily and regardless of the adjacent electronic devices.

In the shown embodiment, the plurality of elongate bars 6 are arranged at several levels, at specific distances D from each other, which distances D may correspond to the height of the electronic device modules 11 to be cooled by the cooling system, such that a modular system of electronic devices may be arranged, and such that they are individually cooled by said cooling system, and individually replaceable from said modular system.

Fig. 9 shows an exploded view of the evaporator 3 of the cooling system 2 and an electronic device 11. Thus, from right, the evaporator 3 includes a first connection pipe 12 and a plurality of inner passages 8, which are to be fitted inside the outer passages 9, which are connected to the second connection pipe 13. Further the electronic device is to be fitted inside a casing 14, which includes openings (not shown) for allowing passage of the outer passages 9 into the recesses 15 of the electronic devices 11. The outer passages 9 are, as indicated above, adapted to be fixed by or fixing means 10, e.g. in the form of screw caps with external threads.

Heat conductive paste may be applied from the front into the opening that surrounds the elongate bars. Subsequently, when the fixing means 10 are screwed onto the connecting means 9a of the elongate bars 6, the paste is pressed inwards by the movement of the fixing means 10, such that virtually all gaps are eliminated. As an alternative, heat conductive paste may be supplied in another way, e.g. in a separate canal, or may be omitted and replaced by another conventional way of ensuring contact for heat conduction.

Above, the invention has been described with reference to shown embodiments. However the invention is not limited to these embodiments, and is only limited by the following claims.

Claims

1. Cooling system (2) for electronic devices (11) installed in a confined space, which cooling system comprises a closed pipe circuit, containing a refrigerant, wherein the closed pipe circuit comprises: an evaporator (3), for evaporating the refrigerant when subjected to heat generated by the electronic devices (11) and thereby cooling said electronic devices (11); a condenser (4), for condensing the thus evaporated refrigerant; and a first and second connection pipe (12, 13) for connecting the evaporator (3) and the condenser (4), wherein the condenser (4) is arranged above the evaporator (3), such that the heavier condensed refrigerant strives downwards through the first connection pipe (12) towards the evaporator (3), and the lighter evaporated refrigerant strives upwards through the second connection pipe (13) towards the condenser (4) thus forming a self-circulating cooling system (2), characterised in that the evaporator (3) comprises a plurality of elongate bars (6) adapted to be arranged in recesses (15) in said electronic devices (11), wherein the elongate bars (6) include an incoming inner passage (8), which is connected to the condenser (4) via the first connection pipe (12), and an outgoing outer passage (9), which is connected to the condenser (4) via the second connection pipe (13), and which is arranged to be in thermal contact with the recesses (15) of the electronic devices (11) such that the heat generated by the electronic devices (11) causes the refrigerant to evaporate as it passes through the outer passage (9) such that the electronic devices (11) are cooled from said recesses; and in that the condenser (4) is cooled by forced ventilation.

2. The cooling system (2) according to claim 1, wherein the condenser (4) is cooled by at least one fan (5).

3. The cooling system (2) according to claim 1 or 2, wherein the elongate bars (6) are adapted to be arranged such that substantially the whole outer surface of the elongate bars (6) is in thermal contact with electronic devices (11).

4. The cooling system (2) according to claim 3, wherein the elongate bars (6) are adapted to be arranged in through holes in said electronic devices (11) such that substantially the whole outer surface of the elongate bars (6) is in thermal contact with the interior of an electronic device (11).

5. The cooling system (2) according to any of the claims 3 or 4, wherein the elongate bars (6) comprise connecting means (9a) for connecting them to fixing means (10) in order to fix an electronic device (10) to the corresponding elongate bar (6), wherein the elongate bars (6) are tubular and arranged to be inserted horizontally from one side of the electronic devices (11), and the fixing means (10) are arranged to be fixed from the opposite side.

6. The cooling system according to claim 5, wherein the elongate bars (6) are arranged to be inserted from a rear side of an electronic device (11) and the fixing means are arranged to be fixed from a front side.

7. The cooling system according to any one of the preceding claims, wherein the plurality of elongate bars (6) are arranged at several levels, at specific distances (D) from each other, which distances (D) correspond to the height of electronic device (11) modules to be cooled by the cooling system (2), such that a modular system of electronic devices (11) may be arranged, such that they are individually cooled by elongate bars (6) of said cooling system (2), and individually replaceable from said modular system.

8. A cabinet including a cooling system according to any one of the preceding claims.

9. The cabinet according to claim 8, wherein m the cabinet is divided into two separate parts by an air tight partition wall (16), an upper part including the condenser, and a lower part including the evaporators and the electronic devices (11) to be cooled.

10. A cabinet according to claim 9, wherein air mlets (5b) and air outlets (5a) are arranged in the upper part for conveying ambient cooling air passed the condenser (4).