AN IMMERSION COOLING SYSTEM

Abstract

A cooling system for cooling of a heat generating electrical component, in particular to reduce the likelihood of overheating of electrical components or chemical breakdown of coolant fluid. The cooling system has a coolant liquid to absorb excess energy from the heat generating electrical component, the coolant liquid having an energy input threshold above which chemical breakdown of the coolant liquid occurs. A cooling module defines a volume containing the coolant liquid, wherein the heat generating electrical component is mounted within the volume and immersed in the coolant liquid. A power input is arranged to supply power into the cooling module to the heat generating electrical component, and a power regulator is provided external to the volume of the cooling module and connected to the power input so as to regulate the power supplied into the cooling module. Cooling systems are also described having coolant liquid comprising dissolved oxygen, having at least one element arranged within the volume comprising aluminium and/or aluminium oxide, and/or having a sealed volume with at least one seal which opens at a predetermined pressure or temperature corresponding to a temperature below the temperature at which the coolant liquid breaks down.

Claims

1. A cooling system for cooling of a heat generating electrical component, comprising: a coolant liquid to absorb excess energy from the heat generating electrical component, wherein the coolant liquid has an energy input threshold above which chemical breakdown of the coolant liquid occurs; a cooling module defining a volume containing the coolant liquid, the heat generating electrical component mounted within the volume and immersed in the coolant liquid; a power input arranged to supply power into the cooling module to energise the heat generating electrical component; and a power regulator, external to the volume of the cooling module and connected to the power input, the power regulator configured to regulate the power supplied into the cooling module such that the excess energy is maintained below the energy input threshold.

2. The cooling system according to claim 1, wherein the power regulator comprises at least one or a combination of the following elements: a voltage regulator, a current regulator, a DC-DC converter, a voltage limiter, a current limiter.

3. The cooling system according to claim 1, wherein the power regulator is arranged at an outer surface of the cooling module.

4. The cooling system according to claim 1, wherein the power regulator is air cooled.

5. The cooling system according to claim 1, wherein the power regulator is thermally connected to a thermally conductive outer surface of the cooling module, such that the outer surface acts as a heat sink to conduct heat away from the power regulator.

6. The cooling system according to claim 5, wherein the thermally conductive outer surface is thermally connected to the coolant liquid such that heat is exchanged with the coolant liquid to cool the thermally conductive outer surface.

7. The cooling system according to claim 1, wherein the power regulator regulates the power supplied to the heat generating electrical component so that the maximum supplied power is substantially constant, the magnitude of the substantially constant maximum supplied power determined according to the power rating of the heat generating electrical component.

8. The cooling system according to claim 7, wherein the magnitude of the substantially constant supplied power matches the power rating of the heat generating electrical component.

9. The cooling system according to claim 1, wherein the power regulator regulates the power supplied to the heat generating electrical component to be within 30% of the power rating of the heat generating electrical component.

10. The cooling system according to claim 1, wherein the power regulator limits the power supplied to the heat generating electrical component to less than a predetermined limit of 200% of the maximum power rating of the heat generating electrical component.

11. The cooling system according to claim 1, wherein all power received at the heat generating electrical component is passed through the power regulator.

12. The cooling system according to claim 1, wherein the power regulator is a first power regulator, and the cooling system further comprises a second power regulator.

13. The cooling system according to claim 12, wherein the first power regulator is arranged external to the cooling module, and the second power regulator is arranged within the sealed volume of the cooling module.

14. (canceled)

15. (canceled)

16. The cooling system according to claim 1, wherein the coolant liquid comprising dissolved oxygen.

17. The cooling system according to claim 1, wherein an element comprising aluminium or aluminium oxide is arranged within the volume of the cooling module.

18. The cooling system according to claim 17, wherein the aluminium or aluminium oxide element is a coating comprising aluminium or aluminium oxide, the coating arranged on at least a portion of an inner surface of the cooling module, the inner surface defining the volume.

19. (canceled)

20. The cooling system according to claim 1, wherein the volume is sealed and the cooling module further comprises a pressure release seal arranged to open the sealed volume of the cooling module when the pressure inside the sealed volume exceeds a threshold pressure.

21. The cooling system according to claim 1, wherein the volume is sealed, and the cooling module further comprises a temperature release seal arranged to open the sealed volume of the cooling module when the temperature inside the sealed volume exceeds a threshold temperature.

22. The cooling system of claim 1, the cooling module further comprising a thermal interface arranged to transfer out of the volume the heat generated by the heat generating electrical component, the heat from the heat generating electrical component being absorbed by the coolant liquid and transported to the thermal interface via a convective current.

23. The cooling system of claim 22, the cooling system further comprising a heat exchanger, arranged to receive heat from the thermal interface and to transport the heat away from the cooling module.

24-66. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0092] A cooling system in accordance with an aspect of the present disclosure is described, by way of example only, with reference to the following drawings, in which:

[0093] FIG. 1 is a projection view of the cooling module arranged to be inserted into a corresponding cabinet;

[0094] FIG. 2 is a cross-sectional view from a first side of a first example of the cooling system;

[0095] FIG. 3 is a plan view of a second side of the first example of the cooling system;

[0096] FIG. 4 is a cross-sectional view from a first side of a second example of the cooling system;

[0097] FIG. 5 is a cross-sectional view from a first side of a third example of the cooling system;

[0098] FIG. 6 is a cross-sectional view from a first side of a fourth example of the cooling system; and

[0099] FIG. 7 is a plan view of a second side of the fourth example of the cooling system.

[0100] Where appropriate, like reference numerals denote like elements in the figures. The figures are not to scale.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

[0101] Referring first to FIG. 1, there is shown a cabinet or chassis 20. This type of cabinet may be used, for instance, within a networked computing environment in order to house a number of data servers.

[0102] The cabinet or chassis 20 is arranged to receive one or more cooling system 10 (also known as cooling blades, or cooling fins). Each cooling system 10 houses one or more heat generating electrical components for operation within a network. For example, each cooling system 10 may house motherboards, central processing units (CPUs) and memory modules to form a data server. Said electrical components can dissipate large amounts of heat, even during normal operation, and so the cooling system is configured to efficiently and effectively remove heat from the vicinity of the electrical components.

[0103] The cabinet 20 is configured having power connectors 14, which are arranged to correspond to a reciprocal power connector 12 arranged at a rear surface of each cooling system 10. The power connectors 12, 14 are arranged to receive an electrical input from the chassis or cabinet 20 to the cooling system 10. The cabinet 20 is connected to an external power source such as mains power or an electrical generator, for example. In most cases, the level of the power (in particular, the voltage) received at the cabinet 20 will be substantially higher than required for normal operation of the electrical components housed within the cooling system 10.

[0104] Further connectors may be present at the cooling system 10 (although not shown in FIG. 1). For example, a connector for input and output of coolant fluid may be present, to connect with a reciprocal connector at the cabinet 20. This may allow circulation of coolant between the cabinet 20 and a heat exchanger in the cooling system 10, for instance. Further connectors present at the cooling system 10 may include data or network connections, plugs or sockets.

[0105] In use, the cooling system 10 is inserted or slotted into the cabinet 20. The cooling system 10 is inserted into the cabinet 20 until the reciprocal power connectors 12, 14 are connected, in order to maintain a power connection. In this example, the power connectors 12, 14 supply a DC voltage from the cabinet 20 to the cooling system 10. Once the cooling system 10 is fully inserted into the cabinet 20, any other types of connectors, plugs or sockets configured between the cabinet 20 and cooling system 10 will also be connected.

[0106] FIG. 2 shows a cross-sectional view of an example configuration for the cooling system 100, with FIG. 3 showing a view of the rear plate of the same cooling system 100. The cooling system 100 can be slotted or inserted into a cabinet or chassis as illustrated in FIG. 1.

[0107] The cooling system 100 comprises a sealable unit or cooling module 110 defining a volume in which at least one heat generating electrical component is housed (for example, mounted on a circuit board 140). At least one internal surface of the cooling module 110 will be arranged as a thermal interface, through which heat can be transferred to a heat exchanger to transfer heat out of the cooling module 110. A variety of sealed connections to the inside of the cooling module 110 may be included for input or output of coolant fluid and/or data or network connections to the components mounted at the circuit board 140. Said electrical components and connections are not shown in FIG. 2.

[0108] Coolant fluid 116 is contained within the volume defined by the cooling module 110. The level of the coolant fluid 116 is sufficient to immerse the heat generating electrical components, thereby creating a large surface area for transfer of heat from the electrical components to the coolant fluid. As a result, the temperature of the coolant fluid 116 closest to the heat generating electrical component is increased. Cooling of the heat generating electrical components may proceed via convection in the cooling fluid, which may subsequently conduct heat from the cooling fluid to a thermal interface with a heat exchanger. The precise cooling mechanism used by the cooling system is beyond the scope of this patent application, but examples of suitable cooling system are described in International Patent Application PCT/GB2014/050616, International Patent Application PCT/GB2010/000950, International Patent Application PCT/GB2014/050615 or U.S. Pat. No. 7,609,518. This invention is not exclusively for use with the systems described therein, however.

[0109] In this example, a coolant liquid 116 is used in which oxygen is dissolved. This has benefits in the event that any chemical breakdown of the coolant liquid occurs, as described further below. However, the configuration shown in FIGS. 2 and 3 could be used with other types of coolant which do not contain dissolved oxygen.

[0110] The cooling system 100 further comprises a power connector 112, a power regulator 120 and a power input 130. The power connector 112 is arranged to allow connection to a reciprocal connector within the cabinet or chassis 20. The power connector 112 receives a DC voltage from a power supply connected to the cabinet 20.

[0111] The power connector 112 is in connection with the power regulator 120. The power regulator 120 is subsequently connected to the power input 130. The power input 130 in this example comprises a connection to a plurality of heat generating electrical components within the cooling system 110 and mounted on the circuit board 140. Accordingly the power input 130 supplies power to the circuit board 140.

[0112] In the present example, the power regulator 120 comprises a voltage regulator and a fully isolated DC-DC converter connected in series. The voltage regulator stabilises the voltage applied to the power input and the DC-DC converter acts to convert or step-down the voltage to a pre-determined level. For example, the cabinet or chassis 20 may receive a power of 60 kW of 48V DC voltage. The power regulator 120 regulates the power such that the voltage passed to the circuit board 140 cannot exceed 720 W. The precise limit for the voltage is set according to the requirements of the electrical components situated at the circuit board 140. The magnitude of the regulated voltage will be pre-determined at the time of manufacture of the cooling system 100. In another particular example of the system shown in FIGS. 2 and 3, the power regulator is configured to pass to the circuit board 140 a voltage not exceeding 400 W.

[0113] In use, a DC voltage is received at the cooling system 100 through the power connector 112. The DC voltage is passed to the power regulator 120 which stabilises the power by regulation of the voltage. The regulated voltage is then passed to the power input 130 to be directed to the circuit board 140 for powering the mounted electrical components. The power regulator prevents excessive power being supplied into the cooling module for use to heat the coolant liquid 116 above tis chemical breakdown temperature.

[0114] The power regulator 120 in FIGS. 2 and 3 is connected to the thermally conductive rear plate 150 of the cooling module. The rear palter 150 acts as a heat sink, dissipating heat from the power regulator during operation. In this example, the thermally conductive rear plate 150 is arranged having the power regulator 120 connected to a first side and the coolant liquid 116 in contact with an opposing second side. As a result, heat can be transferred through the thermally conductive rear plate 150 to the coolant liquid 116, in order to transfer heat away from the power regulator 120. In this way, the power regulator 120 is conductively cooled via the liquid cooling within the cooling module 110. The power regulator 120 is further air cooled by movement of air across the rear plate of the cooling module. In one example, the air flow is generated simply by convection currents, but in a further example the flow of air is driven by one or more mechanical fans. As such, the operating temperature of the power regulator 120 may be reduced.

[0115] Beneficially, in this configuration the power regulator 120 prevents the power input 130 to the cooling module 110 exceeding a predetermined threshold. In this way, the power at the chassis 20 is isolated from the immersion environment. The power regulator 120 acts as a barrier to excess energy ever entering the cooling module 110, and so limits the ability of the heat generating electrical components to heat the coolant fluid 116 and thereby cause chemical breakdown.

[0116] Turning to FIG. 4, a further example of the cooling system is illustrated. FIG. 4 shows a cross-sectional view of a further configuration for a cooling system 400. The cooling system 400 may be slotted or inserted into a cabinet or chassis as illustrated in FIG. 1, and have a rear plate as shown in FIG. 3.

[0117] As discussed above in relation to FIGS. 2 and 3, cooling system 400 comprises a cooling module 110 defining a sealable volume housing a circuit board 140 upon which a plurality of heat generating electrical components are mounted. The volume of the cooling module 110 contains a coolant fluid 116, which is used in combination with a heat exchanger arranged with respect to a thermal interface of the cooling module 110 to convectively cool the electrical components at the circuit board 140.

[0118] The cooling system 400 includes a power connector 112 arranged at an outer surface of the cooling module 110, for connection with a reciprocal power connector at the cabinet or chassis 20. The cooling system 400 further comprises a power regulator 120 connected to a power input 130. The power input 130 is arranged in connection with the circuit board 140 within the cooling module 110, in order to provide power to the electrical components on the circuit board 140. As discussed in relation to FIGS. 2 and 3, the power regulator is used to regulate the power input to the cooling module 110.

[0119] In the configuration illustrated in FIG. 4, the circuit board 140 is immersed in the coolant fluid 116 together with each electrical component mounted at the circuit board 140. As such, the electrical components will be cooled via convection and conduction. Beneficially, using immersion cooling of the electrical components may be an efficient and effective method of cooling.

[0120] The cooling system of FIG. 4 also comprises an element 450 mounted at the circuit board. The element 450 has an aluminium oxide outer coating. In addition, a pressure seal 460 is arranged in the wall of the cooling module 110. The pressure seal 460 is arranged to open when the pressure within the cooling module 110 reaches a threshold pressure. The pressure threshold is selected for a particular coolant and a particular volume of coolant liquid. The pressure threshold pressure corresponds to a predetermined temperature and pressure, where the predetermined temperature is below the temperature required to cause chemical breakdown of the selected coolant in the system.

[0121] In the event of a fault at one or more electrical component, the operating temperature of the faulty electrical component will increase. In this case, more heat is absorbed by the coolant fluid 116 and transferred away from the heat generating component, to be passed to a heat exchanger through a thermal interface. If the heat exchanger cannot remove the heat energy at the rate at which it is absorbed by the coolant fluid 116, the coolant fluid 116 will increase in temperature. This in turn causes the pressure within the cooling module 110 to rise. When the pressure within the cooling module 110 reaches the threshold pressure of the pressure seal 460, the seal opens, allowing the coolant 116 to exit the cooling module 110. At the temperature associated with the threshold pressure, the coolant 116 may be in the gaseous phase, but is at a temperature significantly below that required for chemical breakdown. Accordingly, opening of the pressure valve 460 to depressurise the cooling module 110 and release some of the coolant 116 prevents the continued increase in temperature which could lead to breakdown of the coolant liquid 116. In this way, generation of hazardous chemical breakdown products is avoided.

[0122] If, for any reason, the pressure seal 460 fails to open, the coolant can heat to a temperature at which chemical breakdown of the coolant fluid 116 may begin to occur. As a result, at least small amounts of harmful chemical breakdown products such as PFIB or HF can be generated and contained within the cooling module 110. In this case, the chemical breakdown products react with the element 450 having an aluminium oxide coating. This produces further, less hazardous chemical products in place of the PFIB or HF. In one example, the aluminium in the element 450 reacts with the PFIB to generate a less toxic product, and in a second example the aluminium in the element 450 reacts with the HF to produce a less acidic and corrosive product. Accordingly, the element 450 acts to improve the safety of the operation of the cooling system 400 in the event of a fault.

[0123] FIG. 5 illustrates a cooling module similar to that discussed above in relation to FIGS. 2 and 3. The cooling system 500 may be slotted or inserted into a cabinet or chassis 20 as illustrated in FIG. 1, and have a rear plate as shown in FIG. 3.

[0124] The cooling system 500 comprises a power connector 112, a power regulator 120 and a power input 130 mounted at a rear plate 150 of the cooling module 110. The power input 130 is connected to a circuit board 140, upon which a plurality of heat generating electrical components (not shown) are mounted. The circuit board 140 and heat generating components are immersed in a coolant fluid 116 which contains dissolved oxygen. Cooling of the heat generating components may proceed via convection currents in the coolant fluid 116 as described above in relation to the cooling system of FIG. 1.

[0125] The cooling system 500 further comprises an element 570 coating the inner surface of the walls of the cooling module 110. The element or coating 570 is an anodised aluminium layer (accordingly, comprising aluminium oxide). In this case, anodised aluminium layer 570 covers the full inner surface of the walls of the cooling module 110.

[0126] In addition, the cooling module comprises a temperature relief seal 560 arranged in the wall of the cooling module 110. The material of the temperature relief seal is selected to soften or melt at a threshold temperature below the temperature at which chemical breakdown of the coolant fluid 116 would occur. The threshold temperature is significantly above the normal operating temperatures of the coolant 116 in the cooling system 500.

[0127] In use, if a fault occurs at an electrical component in the cooling module 110, additional heat is transferred to the coolant liquid 116. Where the temperature of the coolant liquid 116 reaches or approaches the threshold temperature of the temperature seal 560, the seal 560 is melted or softened. As a result, a channel into the cooling module 110 is opened. This decreases the pressure within the cooling module 110 may result in release of some coolant fluid 116. As a consequence of the opening of the seal 560, heating of the coolant fluid 116 to the temperature at which chemical breakdown can occur is prevented. Therefore, the seal helps to prevent generation of hazardous chemical breakdown products within the cooling system 110 and offers a further safety feature for the cooling system 500.

[0128] If, for any reason, small amounts of hazardous chemical breakdown products (such as PFIB and HF) are produced, the anodised aluminium layer or coating 570 offers a further safety mechanism. The chemical breakdown products of the coolant fluid 116 react with the aluminium based layer 570 to produce further chemical products which are less hazardous. In this way, the element 570 can act as a sacrificial layer for reaction with the hazardous chemical breakdown products.

[0129] In a specific example, a perfluoropolyether blend (under the trade name Solvay Galden), may be used as the coolant fluid 116 within the cooling system 110. Approximately 4 kg of the coolant fluid 116 may be used within a cooling system suitable to be fitted within a server cabinet or chassis 20. In this specific configuration for the cooling module, the temperature seal 560 is expected to breakdown or open at around 150.sup.C, with the seal melting at a temperature of around 200.sup.C. At around 150.sup.C the pressure in the cooling module is around 6 bar, increasing to approximately 16 bar at around 200.sup.C. The coolant comprising the specific perfluoropolyether blend described will not begin to chemically break down until a sustained temperature of around 250.sup.C is reached.

[0130] FIGS. 6 and 7 illustrate a cooling system similar to the cooling systems of FIGS. 2, 3, 4 and 5. FIG. 6 illustrates a cross-section through the cooling module, with FIG. 7 showing a view of the rear plate. The cooling module comprises a power connector 112, a power input 130 to the cooling module 110, and a circuit board 140 mounted within the cooling module 110. A plurality of heat generating components (not shown) are arranged on the circuit board 140 and immersed in a coolant 116. The coolant contains dissolved oxygen.

[0131] In use, cooling of the heat generating electrical components proceeds by transfer of excess heat to the coolant fluid 116. Heating of the coolant fluid 116 in the vicinity of the heat generating components causes a convention current within the coolant liquid 116 which transfers heat towards a thermal interface with a heat exchanger (not shown). The heat exchanger can then transport the heat away from the cooling system 600. Within the cooling module 110, in normal operation the coolant 116 remains in the liquid phase and does not boil. All circulation of the coolant liquid 116 within the cooling module 110 takes place via convention currents, and the coolant 116 is not pumped.

[0132] In the event of a fault occurring at a heat generating component in the cooling module 110, the coolant liquid 116 may receive heat at a rate faster than the heat can be transferred to the heat exchanger and out of the system. As a result the coolant fluid 116 temperature will increase. Eventually, the coolant fluid 116 will heat to a temperature at which the dissolved oxygen is released or liberated from the coolant 116. The released oxygen gas can then react with the heat generating components to oxidise at least a portion of the component. A heat generating component operating at a higher temperature may be more susceptible to oxidation.

[0133] As a result of oxidation, the heat generated by the heat generating component is reduced. For example, the oxidation may cause an increase in the resistance of the electrical input to the heat generating component. The resistance increase results from a decreased area through which current can be carried as a consequence of the oxidation. An increase in resistance may reduce the current drawn by the electrical component, and so its operating temperature. In some circumstances, the increased resistance may cause the component to fuse, breaking the electrical connection of the heat generating component.

[0134] Accordingly, use of a coolant fluid 116 comprising dissolved oxygen provides a method of halting a runaway increase of temperature of the coolant liquid 116. Consequently, the use of dissolved oxygen in the coolant liquid 116 reduces the likelihood of chemical breakdown of the coolant fluid 116 into hazardous chemical breakdown products (for example, such as PFIB or HF).

[0135] At least four mechanisms for improving the safety of operation of a cooling system have been described herein. Each of these mechanisms may be used independently or in any combination to improve the overall safety of operation of a cooling system.

[0136] Specifically these four mechanisms include: [0137] a) Use of a power regulator to regulate the power supplied into the cooling module of the cooling system. The power being regulated such that the excess energy is maintained below the energy input threshold of a coolant within the cooling module required to undergo chemical breakdown. [0138] b) Use of an aluminium or aluminium oxide element (such as an anodised aluminium layer or an aluminium component) within the volume of the cooling module to react with at least some chemical breakdown products of the coolant fluid. After the reaction of the chemical breakdown products with the element, the resultant products may be less hazardous or less acidic. [0139] c) Use of a coolant comprising dissolved oxygen. The dissolved oxygen may be liberated or released from the coolant if the coolant liquid is heated above a certain temperature. The released oxygen may react with a portion of an electrical component or component within the cooling module to at least partially oxidise the component. For example, the electrical input to a heat generating component may be oxidised such that the resistance of an electrical current to the heat generating component is greatly increased. The increased resistance may cause the component to fuse. As a result, the excessive heating of the heat generating component is halted. [0140] d) Use of a temperature or pressure relief seal to vent the cooling module before a pressure and temperature is reached that could result in chemical breakdown of the coolant fluid within the cooling module.

[0141] Many combinations, modifications, or alterations to the features of the above embodiments will be readily apparent to the skilled person and are intended to form part of the invention. Any of the features described specifically relating to one embodiment or example may be used in any other embodiment by making the appropriate changes.

[0142] For example, in the specific examples discussed above in relation to FIGS. 2 and 3, the power regulator is either a voltage regulator or a voltage regulator and a fully isolated DC-DC converter connected in series. However, the power regulator may be any electrical component or circuit which acts to stabilise or control the power input to the cooling module (and in particular, to the electrical components at the circuit board within the cooling module). As would be understood by the skilled person, a power regulator could comprise circuitry for voltage regulation, current regulation, current limitation, voltage limitation, or any combination of these components.

[0143] In FIGS. 2 and 3 discussed above, the power regulator is arranged to be attached to the rear plate of the cooling module and so external to the cooling module. In the example shown, the rear plate is the surface of the cooling module received by the cabinet or chassis and upon which the power connector to the cabinet or chassis is mounted. However, in another example the power regulator could be arranged at a different position or on a different surface of the cooling module whilst being kept external to the cooling module. In a still further example, the power regulator could be arranged at the cabinet or chassis but in series with the power input to the cooling module. In either case, all electrical connections to the electrical components are routed through the power regulator. In most cases, the power regulator will be directly adjacent the power input, such that the power regulator and power input are arranged in series as neighbouring components in the electrical circuit. Ideally, a particular power regulator acts exclusively to regulate the power entering a particular single cooling system or cooling fin.

[0144] Although each of the embodiments described above are described as using a coolant containing dissolved oxygen, a coolant that has been degassed or without dissolved oxygen could be used within the illustrated cooling systems. Alternatively, a coolant fluid containing any dissolved gas comprising oxygen may be used. In particular, the dissolved oxygen could be dissolved in the coolant in the form of pure oxygen. Alternatively, the dissolved oxygen could be provided as a component of a dissolved gas having more than 21% oxygen by volume (in other words, a dissolved gas comprising an oxygen content more than that of air). For example, the oxygen content of the dissolved gas may be 25% or more, 50% or more, or 75% or more. Pure oxygen may have an oxygen content of more than 99%.

[0145] In the embodiment of FIG. 4, the element is a separate element having an aluminium oxide coating. FIG. 5 shows the element being a coating on the inner surface of the walls of the cooling module. However, in other examples the element may take different forms. For example, the element may be a sacrificial element comprised only of aluminium or aluminium oxide, or the element may be as a coating on the heat transfer surface or thermal interface (not shown).

[0146] In the specific embodiment discussed above in relation to FIG. 5, the coolant fluid is perfluoropolyether, PFPE (for instance Solvay Galden). The particular pressures and temperatures recited in relation to FIG. 5 for opening of the temperature seal are provided specifically for perfluoropolyether and a cooling system having a size to fit within an Iceotope Limited chassis or server cabinet. However, other types of coolant could be used, or the volume of the cooling module may be a different size. In this situation the appropriate threshold temperatures and pressures for a temperature or pressure seal should be chosen. As an example, coolant fluids containing fluoro-octanes (for instance Fluorinert), HFE (for instance Novec), hydrofluorolefin, HFO (for instance Vertrel Sinara), perfluoroketone, PFK (for instance by Novec) could also be used. Each of these coolant fluids demonstrates similar boiling temperatures. However, some may have a lower chemical breakdown temperature (for example, HFE/PFK by Novec can begin to breakdown at around 150.sup.C compared to a breakdown temperature of 250.sup.C for perfluoropolyether by Solvay Galden). Accordingly, use of Novec would require an appropriate selection of threshold pressure and temperature for a pressure or temperature seal. For example, a different material could be selected for use within the seal. The seals should also be selected for materials compatibility and permeability with the coolant fluid.