GB2511354A

GB2511354A - A module for cooling one or more heat generating components

Info

Publication number: GB2511354A
Application number: GB1303655.3A
Authority: GB
Inventors: Peter Hopton; Jason Bent; Keith Deakin
Original assignee: Iceotope Ltd
Current assignee: Iceotope Ltd
Priority date: 2013-03-01
Filing date: 2013-03-01
Publication date: 2014-09-03
Also published as: GB201303655D0; WO2014132085A1

Abstract

A module 10 for cooling a heat generating component, comprises a container 12 defining a volume for containing a coolant. The container has: a planar cooling system 14; a planar heat generating component 20, mounted within the volume so that the cooling system is spaced apart from the heat generating component and so that the plane of the cooling system and the plane of the heat generating component are parallel, thereby allowing the cooling system to remove heat from the heat generating component via the coolant; and a wadding material 18, disposed adjacent the heat generating component within the volume and having a capillary action so as to route coolant towards a surface of the heat generating component. The heat generating component may be an electronic device on a board. The cooling system may be a condenser 22. The wadding material may be electrically insulating e.g. cotton wool, paper, cellulose, silica. The coolant may be a dielectric or inert. Electrical inlets to the container may be present. Inlets 40 and outlets 30 for the coolant may be included.

Description

A module for cooling one or more heat generating components

Field of the Invention

The present invention relates to a module for cooling heat generating components, a method of manufacture for a module for cooling heat generating components, and a method of operation for a module for cooling heat generating components.

In particular, this invention is applicable for the cooling of electrical computer components, for example motherboards, processors or memory modules.

Background to the Invention

Many types of electrical component generate heat during operation. In particular, electrical computer components such as motherboards, central processing units (CPUs) and memory modules may dissipate substantial amounts of heat when in use.

In more modern computers, improved performance and an increasing density of components on a circuit board results in excessive guantities of generated heat. Heating of the electrical components to high temperatures can cause damage or affect performance. Of particular concern are data processing or computer server centres where a substantial number of heat generating components are co-located and yet require reliable, continuous operation over a long time period.

A variety of cooling systems are presently employed to remove heat from the vicinity of electrical computer components. A common solution uses fans to force a continuous supply of cooled air over the components. However, fan cooling may be noisy, cumbersome and require high volumes of circulating air in order to effectively cool the components to acceptable operating temperatures.

More advanced cooling assemblies use liquid cccling.

Liquid cooling systems may be advantageous over air cooled systems as they allow removal of heat using both conduotion and convention. In general, convection currents demonstrate more efficient heat transfer than via conduction alone.

Furthermore, appropriate selection of the coolant (acoording to its freezing point) may permit the stable temperature of the system to be lowered dramatically.

A number of assemblies for liquid cooling have been demonstrated. In general, the electrical components are immersed in the coolant, so providing a large surface area for heat exchange between the heat generating components and the liquid. Previous immersive liquid cooling assemblies represent one of two types: (a) non-phase change cooling systems, in which the coolant does not change phase and remains liquid at all times; and (b) phase change cooling systems, in which the coolant undergoes a phase change to become a gas, thereby removing energy from the system and reducing temperature. In non-phase change cooling systems, heat is removed from the coolant via conduction to a heat exchanger or similar cooling arrangement. In general, phase change cooling allows better handling of high heat densities, without higher temperature gradients.

A non-phase change cooling system is described in WO- 2010/130993 having common inventorship with this present invention. Here, convection currents in a first coolant convey heat away from heat generating components. A conduction plate is arranged adjacent the heat generating components such that the first coolant is in direct contact with a first surface of the conduction plate. The conducting plate acts as a heat exchanger to a second coolant, which is circulated thus extracting heat from the system.

In contrast, US-2007/109742 and GB-2432460 (both having common inventorship with this present invention) consider a phase change cooling system. In operation, heat from a motherboard immersed in a primary coolant within an air-tight container may be dissipated to the surrounding primary coolant. As a result, the primary coclant undergoes a phase change to become a gas. Convention currents cause the less dense gas to move upward through the primary coolant, whilst cooler liquid is mcved downwards towards the mctherbcard. A condensing coil (or evaporation coil) in the upper section of the air-tight container causes the cooling gas to return to a liquid, and by so doing remcves heat from the system. The condensing coil operates via a separate, secondary circulation system with a secondary coolant.

A phase change cooling system is also ccnsidered in US 4,912,548 which describes a package for a semiconductor device, the package having an integrated heat pipe. The semiconductor device is immersed in cooling fluid and located directly below the heat pipe. The heat pipe is substantially vertical, with a cavity at its centre and a wicking material around its inner surface. An upper portion of the heat pipe is provided with cooling fins and is maintained at a cold temperature. Operation of the semiconductor device causes the coolant to boil. The coolant vapour rises through the centre of the heat pipe, transferring heat away from the device, until it oontacts the cold portion of the heat pipe. Here, the vapour condenses and the coolant is carried back down the heat pipe via the wioking material.At the base of the heat pipe, the liguid droplets are returned to the pool of coolant in which the semiconductor device is immersed. In an alternative embodiment, the device is not immersed in coolant, and the coolant is instead retained in wadding material at the base of the beat pipe.

The capacity of a cooling system to remove heat may be quantified by its cooling power. This describes the rate of energy transfer out of the system to the exterior. The increasing heat load of modern electrical computer components may require a cooling power of 3-5kw to maintain a desirable operating temperature. However, existing cooling systems, as described above, are more appropriate for systems requiring a lower cooling power.

In some existing systems, the efficient transfer of heat from the heat generating components to the heat exchanger can be disrupted by the positioning and configuration of multiple heat generating components or electrical devices within the assembly. For example, the arrangement of electrical devices on a circuit board, each having a different shape and elevation from the board, can disrupt the movement of convection currents and result in turbulent flow.

Consequently, voids may arise between components in which there is a diminished flow of coolant, whilst other regions of the system experience more consistent circulation of coolant.

As a result, "hot spots" occur within the system.

Further complications are noted with respect to the seal at inlets to the air-tight container (for example, filling inlets, or inlets for electrical connections) . If the operating pressure inside the module is greater than atmospheric pressure, the seals make leak causing loss of coolant to the outside and entrance of air and moisture into the module. Consequently, the system must be regularly maintained to replenish coolant levels and/or replace seals.

Furthermore, air vapour and moisture will accumulate in the module and reduce the efficiency of heat exchange between the coolant and condenser or cooling system.

Leakage of air and moisture into the module can significantly reduce the performance of cooling system as described above. In most systems, the condenser is positioned above the coolant and heat generating component, in the same region of the module as the vapour gap. In this configuration, stratification of the air vapour and coolant vapour can occur, such that the air vapour accumulates around the condenser. Thus, the capacity of the condenser to cool gaseous coolant is impaired.

To overcome this problem, some cooling systems actively pump coolant around the system to be dispersed as a spray or jet. This can break-up stratified layers of coolant vapour and air vapour present in the system. However, there remains a difficulty in achieving effective pumping of common coolants at a temperature close to boiling point. Consequently, provision of an improved method of efficient cooling of heat generating components is sought.

Summary of the Invention

Against this background, the present invention relates to a module for cooling heat generating components, for example, for cooling electronic computer components such as a circuit board comprising a central processing unit and memory modules.

The cooling system is typically a phase-change cooling system in which one or more heat generating components are affixed within a sealable or air-tight container.

The heat generating components are positioned in close proximity to a wadding material having a capillary action.

The wadding material is disposed adjacent to or in contact with a surface of the heat generating component. A coolant is retained within the container and is principally absorbed within the wadding material such that the wadding material remains dampened or moist. Operation of the heat generating component causes the coolant retained in nearby portion portions of the wadding materiai to evaporate and form a gas.

The gaseous coolant transters heat away trom the heat generating components and towards an adjacent cooling system or heat exchanger via convection currents. The cooling system causes the gaseous coolant to condense, thus removing heat from the system.

Efficiency of cooling is significantly improved by the incorporation of the wadding material with a capillary or hygroscopic action, adjacent to the heat generating component.

The wadding material assists the effective circulation of coolant between the heat generating component and cooling system. In particular, the capillary action of the wadding material acts to route or deliver coolant that has been re-condensed at the cooling system (and having a lower temperature) directly to the surface of the heat generating component. By so doing, the wadding material may aid uniform distribution of the coolant around the system and so negate "hot-spots" resulting from disruption or turbulence of the flow of convection currents around heat generating components in the assembly.

The wadding material further allows self-regulation of the rate of circulation of the coolant within the cooling module: the rate at which coolant is delivered to the heat generating component depends directly upon the rate of boiling of the liquid and the maximum fiow rate of the capillaries.

As such, for heat generating components operating at lower powers (and so generating less heat) the rate of circulation of coolant is less. Conversely, for higher power devices the rate of circulation will be greater and the cooling power increased. This mechanism helps to maintain a stable pressure within the cooling module, ideaily at close to atmospheric pressure.

According to a first aspect of the invention there is a module for cooling a heat generating component. The module comprises a container suitable for containing a coolant, the container having a cooling system or heat exchanger which is substantially planar, and a heat generating component which is substantially planar, each mounted therein. The heat generating component is located within the container spaced apart from the cooling system. Furthermore, the heat generating component and cooling system are arranged so that the plane of the cooling system and the plane of the heat generating component are substantially parallel. This arrangement allows the cooling system to remove heat from the heat generating component via the coolant. The invention further comprises a wadding material having a capillary or wioking action. The wadding material is disposed adjacent the heat generating component and is arranged such that its capillary action routes or delivers coolant towards one or more surfaces of the heat generating component. The wadding is arranged to be in close proximity to, or in contact with, one or more surfaces of the heat generating component.

The capillary action of the wadding material advantageously directs coolant of a lower temperature from the vicinity of the cooling system directly to the vicinity of the heat generating component. Thus, the capillary action improves the efficient circulation of coolant within the system, thereby transferring heat away from the heat generating component. Consequently, there may be a more homogenous temperature distribution across the surface area of the heat generating component.

In addition, the wadding material having a capillary action assists circulation of the coolant via passive (rather than mechanical) means. For example, the module does not reguire circulation of the coolant by a pump.

The cooling system and heat generating component are substantially planar. In other words, the cooling system and heat generating component each have a depth that is much less than its length and width. The surfaces defined by the axis of length and width comprise the planar face of the cooling system or heat generating component.

The heat generating component may be arranged within the container such that a planar face of the cooling system and a planar face of the heat generating component are facing each other. In other words, a planar face of the cooling system is both opposite and substantially parallel to the planar face of the heat generating component. For example, the heat generating component and the cooling system may both be planar and rectangular in shape, arranged so that the longest sides of each rectangle are parallel. This configuration may provide a large surface area of opposing planar surfaces of the heat generating component and the cooling system, thus enabling effective cooling. Alternatively, the cooling system may not be rectangular, and may instead be a square or another substantially planar shape. Similarly, the heat generating component may be of any substantially planar shape.

Preferably, the wadding material is disposed between the cooling system and the heat generating component. For example, the wadding material may be interposed between the parallel and opposing planar faces of the heat generating component and cooling system, and may substantially fill the space therebetween. There may be a uniform density of wadding material in the region between the cooling system and heat generating component. Alternatively, a greater density of wadding material may be positioned adjacent particular portions of the heat generating component.

The wadding material may be in contact with, or in close proximity to, the surface of the cooling system. Beneficially, the wadding material is arranged such that its capillary action routes or channels coolant from the vicinity of the cooling system toward the surface of the heat generating component. The arrangement of the wadding material thereby influences the flow or circulation of coolant around the module. The wadding material can be used to constrain or adapt the normal flow of coolant that would occur due to convection currents, in order to ensure more efficient heat transfer. For example, the wadding material may be arranged so that the capillary action moves the lowest temperature coolant horizontally in the system, between the parallel and opposing planar faces of the cooling system and heat generating component, rather than allowing it to flow downwards to the base of the container (as would be the case, by the action of gravity, without the wadding material) Optionally, within a particular cooling assembly the wadding may further be arranged so that the capillary action routes coolant toward particular regions of the heat generating component, as required. For example, the capillary action may be configured to move low temperature coolant to a "hot spot" on the heat generating component. Alternatively, the wadding material will be uniformly distributed in the vicinity of the heat generating component. The wadding may be arranged to provide wadding adjacent to or in contact with the whole surface of the beat generating component.

The heat generating component may be affixed within the container such that, in use, the plane of the heat generating component is substantially vertical. In other words, the heat generating component may he mounted so that, in use, its planar face (or axis of elongation) is upright (or perpendicular to the base of the container) Optionally, the cooling system may be positioned within the container such that, in use, the plane of the cooling system is substantially vertical. For example, the cooling system may be mounted so that, in use, its planar face (or axis of elongation) is upright (or perpendicular with respect to the base of the container) Advantageously, the cooling system and heat generating component may be arranged vertically and parallel. For example, the heat generating component and cooling system may each be substantially planar and mounted vertically and facing each other within the container, with wadding interposed between. This increases performance of the cooling system, whilst also allowing more compact design.

A vapour space may be defined in an upper region of the container above the heat generating component and wadding.

For example, in use, the lid or top surface of the container may be spaced apart from the uppermost surface of the heat generating component. The space therebetween may define a vapour space in which air vapour (including water vapour) can accumulate.

Advantageously, the cooling system is located within the container such that the operational portion of the cooling system is below the vapour space. The operational portion may be the portion of the surface of the cooling system which is adjacent the wadding material. As a result, if stratification of air vapour and coolant vapour occurs, the air vapour may collect in the vapour space. Thus, the majority of the operational portion of the cooling system is in contact with coolant and can cool the heat generating component more effectively.

In a further aspect of the present invention, there is module for cooling a plurality of heat generating components comprising a container suitable for containing a coolant, the container having a cooling system and a plurality of heat generating components spaced apart within the container. The module further comprises a wadding material interposed between the plurality of heat generating components, the wadding material having a capillary action so as to route coolant towards the surfaces of the plurality of heat generating components. Advantageously, the wadding material assists in efficient cooling of multiple heat generating components (in other words, two or more separate heat generating components), as it increases the cooling capacity of the module.

The plurality of heat generating components may each be separate electronic devices. For example the plurality of heat generating components may be processors, memory modules or controllers or any combination of these.

The plurality of heat generating components may each he substantially planar. In other words, the may each have a length and width which is much greater then their depth. The axis of length and width may define a planar face of the heat generating component.

The plurality of heat generating components may each comprise one or more electronic devices mounted on the surface of a planar board. For example, each heat generating component may be a circuit board or mother board with one or more devices such as a memory module, processor or controller (or combination of these) mounted on its surface. The plurality of heat generating components will comprise a plurality of such circuit boards.

Optionally, the plurality of heat generating components may be fixed within the container such that the plane of each heat generating component is substantially vertical. In other words, in use, the plane of each heat generating component is substantially upright and perpendicular to the base of the container. Each heat generating component may be arranged upright and be parallel with respect to another so that the plane of each heat generating component is parallel to the plane of the next heat generating component. A wadding material may be interposed between the heat generating components, such that the wadding material is adjacent the surface of the heat generating components.

Preferably, the plurality of heat generating components are affixed within the container such that the plane of each heat generating component is perpendicular to an axis of elongation of the cooling system. The cooling system may be affixed within the container such that, in use, the cooling system is arranged substantially horizontally in the container.

The plurality of heat generating components may be positioned within the container such that, in use, the cooling system is positioned above the plurality heat generating components and wadding material. As such, in use, the uppermost portion of the wadding material and the uppermost portion of the plurality of heat generating components will be below the cooling system. The uppermost surface of the wadding material may be facing the cooling system.

Consequently, any coolant which is condensed by the cooling system will fall on to the heat generating components and wadding material, thus re-dampening the wadding material and increasing the effectiveness of cooling.

It will be understood that in the following description, use of the term "heat generating component" may apply to either a single heat generating component, one of a plurality of heat generating components or a plurality of heat generating components.

A heat generating component may be any electronic device.

More particularly, the heat generating component may comprise an electronic computer component such as a circuit board, processor or memory module, and especially any combination of these. The heat generating component may be formed of a planar board with one or more electronic devices mounted on its surface. The heat generating component or mounted electronic devices may be comprise a heat spreader or coating to assist the exchange of heat with the coolant.

In operation, the heat generating component generates heat which stimulates convection currents within the coolant.

In particular, operation of the heat generating component may cause a portion of the coolant in the vicinity of the heat generating component to evaporate (or boil) and change phase from liquid to gas. Accordingly, a heat generating component may be any component which produces heat as a by-product of its operation.

Preferably, the cooling system includes a condenser or evaporator coil. The condenser offers an efficient means of extracting heat from the system by causing gaseous coolant to condense and return to the liquid phase. As a result, said portion of the coolant will have reduced in temperature. The condenser may be a coil or may consist of a surface having embedded fluid channels.

Preferably, the wadding material is insulating, particularly electrically insulating. This reduces the likelihood of damage to the heat generating component, which may be an electrostatic-sensitive device, through contact with

an electric field.

The wadding material may comprise of one or more of: cotton wool, paper, cellulose, silica, a metal or a metal oxide. These materials are particularly suitable due to their having a superior capillary or wicking action. Beneficially, the material may be a hygrosoopio substance.

Preferably, a coolant is contained within the container and more specifically is retained or absorbed by the wadding material. The coolant provides a medium for effective transfer of heat away from the heat generating component, in particular via convection currents. The coolant is able to exploit the capillary action of the wadding material.

Ideally, the volume of coolant contained within the container is sufficient to uniformly moisten or dampen the wadding material. The coolant absorbed and retained by the wadding material may be a mixture of coolant in the liquid and gaseous phases. Preferably, the amount of liquid retained by the wadding will be sufficient to promote effective and consistent circulation of coolant in the proximity of every region of the surface of the heat generating component adjacent the wadding.

Beneficially, inclusion of the wadding material results in a lower volume of coolant necessary for effective cooling than compared with cooling systems in which the heat generating component is fully submerged by a cooling liquid. For operation of the present invention, the wadding need only be dampened with coolant, rather than the heat generating components within the container being immersed.

The coolant may be a dielectric (or insulating) liguid and/or may be inert. Advantageously, this reduces damage to electrostatic-sensitive heat generating components caused by an electric current being applied between components via the coolant.

The coolant may be a fluorinated compound. Fluorinated compounds are especially suited for use in combination with the wadding material having a capillary action. Examples of preferred fluorinated compounds include perflouroketones (PFK) or hydrofluroethylene (HFE) . The compound may be chosen to have a boiling point at close to the operating temperature of the heat generating component and a freezing point below 000.

The module for cooling a heat generating component may further comprise an electrical inlet to the container, through which electrical connections to the heat generating electrical component or other electrical components can be received. The electrical inlet further comprises a seal to prevent coolant escaping the container and to prevent air or moisture entering the container from the exterior.

The electrical inlet may be located on a wall of the container at a height that is greater than the heat generating component within the container. Optionally, the electrical inlet is located on a wall of the container at a height greater than the height of the cooling system within the container. Accordingly, the electrical inlet may be arranged such that it is located in the vapour space, and in particular in the lid or upper surface of the container. Advantageously, the interior of the container may be maintained at atmospheric pressure and so leakage of air into the container through the seal of the electrical inlet is reduced.

The module may be fully sealed, so that the container is air-tight and has no inlet or outlet other than the electrical inlet. Alternatively, the module for cooling a heat generating component may further comprise a filling inlet to the container, through which the coolant can be received into the container. The inlet may comprise a seal. Beneficially, inclusion of the filling inlet allows straightforward refilling of the coolant in order that the coolant can be maintained at its optimum level for efficient cooling.

Optionally, the seal to the filling inlet may include a one-way valve, or other type of valve. Beneficially, the seal may be designed to allow filling of the container with coolant without exoessive spillage or mess.

The filling inlet may be positioned in the upper wall (or lid) at the top of the container, or in the wall of the container at a height greater than the height of the heat generating component. Thus, in use, the filling inlet may be in the vapour gap above the wadding and heat generating component. Alternatively, the filling inlet may be located on the wall of the container at a height that is no higher then the height of the heat generating component within the container when the module is in use. In other words, the filling inlet may he positioned so that the distance between the filling inlet and the base of the container is less than the distance between the uppermost portion of the heat generating component and the base of the container. This may allow improved filling of the container.

Preferably, the module for cooling a heat generating component further comprises a feedback outlet from the container. Excess coolant in the gas or liquid phase may exit the container through the feedback outlet. The feedback outlet may further comprise a valve. The valve may be a pressure release valve and/or be controlled externally by the user to adjust the rate of flow of gaseous coolant through the valve. Provision of the valve enables adjustment of the volume of coolant passing out of the container, and may also act as a safety feature to avoid the build up of excess pressure within the container. The pressure within the container may be maintained at close to atmospheric pressure, which reduces the likelihood of leakage at the filling inlet, electrical inlet or any other seal of the container.

Optionally, the module for cooling a heat generating component according to any preceding claim may further comprise a feedback inlet to the container. A valve may be placed at the feedback inlet to regulate the flow of coolant into the container. The valve may be any type of valve, and may be manually controlled or controlled by a controller.

In some embodiments, a secondary circulatory system is connected between the feedback outlet of the container and the feedback inlet of the container, for circulation of coolant.

The secondary circulatory system may act to provide a supplementary means, external to the container, for circulation of the coolant. The secondary circulatory system receives coolant from the feedback outlet of the container and returns the coolant to the container through the feedback inlet. The secondary circulatory system may redistribute the coolant around the module in order to result in more effective cooling. Furthermore, the secondary circulatory system may give redundancy for storing any overflow or excess gaseous coolant which would otherwise cause the container to exceed an optimum pressure. Moreover, the secondary circulatory system may provide an alternative and/or additional method of cooling gaseous coolant, thereby increasing the system cooling power or cooling capacity. Furthermore, the secondary circulatory system may be connected to more than one module containing heat generating components. The secondary circulatory system may be central to a network of modules.

The secondary circulatory system may comprise a pump or other mechanical means for transfer of coolant. The secondary circulatory system may further comprise a storage tank suitable for containing coolant. The pump and storage tank may be placed in series between the feedback outlet and feedback inlet, interconnected by pipes. The secondary circulatory system incorporating a pump or other mechanical means may advantageously allow coolant to be redistributed around the container. For example, coolant may be pumped from the feedback outlet in a lower region of the container to the feedback inlet in the upper region of the container, against the action of gravity. This may be particularly useful to re-dampen or re-wet wadding material in the upper portion of the container, in order to maintain optimum dampness for effective cooling.

Alternatively, the secondary circulatory system may comprise a secondary cooling system arranged to receive gaseous coolant released through the feedback outlet. The secondary cooling system can increase redundancy and the overall cooling capacity of the system. The secondary cooling system may provide an additional or auxiliary method for cooling excess gaseous coolant, in order to avoid excessive pressures or excessive load on the cooling system situated within the container.

The secondary cooling system may further comprise a secondary condenser or heat exchanger arranged to condense gaseous coolant released through the feedback outlet of the container and may further comprise a storage tank suitable for containing the oondensed coolant. The secondary condenser or heat exchanger may remove heat from the system and return the coolant to the liquid phase. Storage of re-condensed coolant within the storage tank provides utility for regulating the flow of coolant out of the secondary cooling system, allowing flow to be adjusted according to need. The secondary cooling system may form part of the secondary circulatory system as follows: the gaseous coolant exits the container through the feedback outlet (and/or valve) of the container and enters the secondary cooling system. The gaseous coolant may be cooled by the secondary condenser, and re-condensed to the liquid phase. The re-condensed coolant may be retained in the storage tank until required for return to the container. When needed, the coolant may be resupplied to the container through a feedback inlet (and/or valve) located in a wall of the container. Beneficially, there may be a closed circulation system for the coolant, allowing the user to adjust the coolant level within the container in order to maintain an optimum liquid level.

The feedback inlet may further comprise a spray nozzle within the container, arranged such that coolant entering the container through the feedback inlet passes through the spray nozzle. The spray nozzle generates a mist or series of droplets of coolant for entry to the container. This may provide a consistent and uniform distribution of the coolant, for example across the upper surface of the wadding material.

In addition, a mist or spray of droplets of coolant may be less likely to disrupt convection currents and so the intended transfer of heat within the system.

Optionally, the secondary cooling system may comprise a controller to control the flow of coolant into and out of the container at the feedback outlet and/or inlet. The controller may control a valve at the feedback outlet of the container or a valve at the feedback inlet, or any combination of valves within the module. The valves may determine flow of the coolant into or out of the container or may shut-off the flow of coolant entirely. The controller may be a computer or a manually operated switch or other controlling means.

Preferably, the module comprises one or more sensors for measuring one or more parameters consisting of: liquid level; moisture level or dampness within the wadding; and, pressure with the container. The one or more sensors may be located in the wall of the container. More than one sensor may be distributed in the walls of the container to measure a parameter within particular locality. For example, sensors may be arranged at a number of heights within the container.

The sensors may be electrically connected to the exterior of the module to allow measurement of each variable without disturbance of the module (for example, the sensors may be electrically connected through the electrical inlet to allow measurement, without the requirement to access the interior of the container) The controller may be arranged to adjust the flow of the coolant through the feedback inlet based on the measured parameter from the one or more sensors. Optionally, the controller may adjust a valve at the outlet of the container according to a value from the one cr more sensors. This is particularly advantageous when forming part of a secondary circulatory system and may ensure that the optimum amount of coolant is present in the wadding material, or that the optimum pressure is maintained within the container.

The one or more sensors may be capacitive sensors. For example, a sensor may be a capacitive sensor for measuring liguid level. Alternatively, a sensor may measure the capacitance between two plates with wadding there-between, in order to ascertain the dampness of the wadding. In contrast, the one or more sensors may include a liguid level meter incorporating a float.

According to an additional aspect of the invention there is provided a method of manufacturing a module for cooling a heat generating component which comprises a first step of providing a container suitable for containing a coolant. The method further comprises a second step of hcusing a substantially planar cooling system within the container. A third step comprises mounting a substantially planar heat generating component within the container, located so that the cooling system is spaced apart from the heat generating component and so that the plane of the cooling system and the plane of the heat generating component is substantially parallel. This allows the cooling system to remove heat from the heat generating component via the coolant. Finally, the method includes providing a wadding material adjacent the heat generating component, the wadding material having a capillary action routing coolant towards a surface of the heat generating component.

The method may further comprise providing a coolant within the container in order to dampen the wadding.

Housing the substantially planar cooling system may comprise housing the cooling system so that, in use, the -20 -cooling system is substantially vertical within the container.

In other words, in use, the cooling system is upright within the container, and the plane of the cooling system is perpendicular to the base of the container.

Preferably, mounting the substantially planar heat generating component comprises mounting the heat generating component substantially vertically within the container.

Accordingly, in use, the heat generating component may be upright within the container, with the plane of the heat generating component being perpendicular to the base of the container. The planes of heat generating component and cooling system may be substantially parallel in order that the planar surfaces of the heat generating component and cooling system are opposite and facing each other.

It will be understood that method features corresponding with the structural, apparatus features described herein may optionally be provided in conjunction with the above-described method.

According to a still further aspect of the invention there is provided a method of operating a module for cooling a substantially planar heat generating component, mounted within a container and adjacent a wadding material having a capillary action. The wadding material retains a coolant, so that the step of operating the heat generating component causes a portion of the coolant to evaporate. The method further comprising condensing the evaporated gaseous coolant using a substantially planar cooling system, the cooling system being spaced apart from the heat generating component with the plane of the heat generating component and the plane of the cooling system being substantially parallel.

Again, it will be understood that this method may comprise optional method steps corresponding with any one or more of the apparatus features defined herein.

In a further aspect of the present invention, there is provided a method of manufacture of a module for cooling a -21 -plurality of heat generating components. Said method comprises a first step of providing a container suitable for containing a coolant, and a second step of housing a cooling system within the container. A further step comprises mounting a plurality of heat generating components within the container. A final step comprises providing a wadding material adjacent the plurality of heat generating components, the wadding material having a capillary action which routes coolant towards the surfaces of the plurality of the heat generating components.

Preferably, the method further comprised an additional step of providing coolant within the container in order to dampen the wadding material.

Optionally, mounting a plurality of heat generating components within the container comprises mounting the plurality of heat generating components within the container such that they are located below the cooling system, thereby allowing the cooling system to remove heat from the plurality of heat generating components via the coolant.

The combination of any of the apparatus or method features described herein, or the combination of both apparatus and method features, is also provided even if not explicitly disclosed.

Brief Description of the Drawings

Preferred embodiments of the present invention will now be described by way of example only, with reference to the accompanying drawings in which: -22 -FIGURE 1 is a simplified cross-sectional side view of a module for cooling a beat generating component; FIGURE 2 is a simplified cross-sectional side view of an alternative embodiment of a module for cooling a heat generating component; FIGURE 3 is a simplified cross-sectional side view of a further alternative embodiment of a module for cooling a heat generating component.

It should be noted that the figures are not necessarily drawn to scale.

Specific Description of a Preferred Embodiment

Referring first to Figure 1, there is shown a simplified cross-sectional side view of a module 10 for cooling a heat generating component. The module 10 comprises a container 12 suitable for containing a coolant. Within the container 12 is a cooling system 14, together with a heat generating component affixed to a mounting 16, and positioned spaced apart from the cooling system 14. Disposed between the cooling system 14 and the heat generating component 20 is a wadding material 18 having a capillary action. The embodiment of the invention illustrated in Figure 1 further comprises: a condenser 22, included within the cooling system and consisting of fluid carrying channels embedded into a cooling surface; a feedback outlet 30 of the container; a secondary circulatory system comprising a secondary cooling system 32; a valve 34, at the feedback outlet; a secondary condenser 36 and storage tank 38 as part of the secondary cooling system 32; a feedback inlet to the container; a controller 42; and, a spray nozzle at the feedback inlet. The embodiment also incorporates a coolant retained or absorbed within the wadding material.

Although not shown in Figure 1, the embodiment comprises a -23 -filling inlet to the container and a seal at the filling inlet, as well as a number of measurement sensors.

Figure 1 illustrates the module 10 comprising the heat generating component 20 affixed to the mounting 16, where the heat generating component 20 is a circuit board including a number of surface mount components such as a central processing unit and one or more memory modules.

The mounting 16 is located within the container 12 so that, when affixed, the heat generating component 20 is spaced apart from the cooling system 14. The distance between the heat generating component 20 and the cooling system 14 is selected to support optimum cooling in the system. For example, the positioning of each feature is selected to ensure favourable flow of convection currents created within the system when in operation.

The wadding material 18 with a capillary or wicking action is Interposed between the cooling system 14 and heat generating component 20. The wadding material 18 is arranged so that it is close to, or in contact with, both the outer surfaces of the heat generating component 20 and a surface of the cooling system 14. Ideally, the wadding material 18 is arranged to be in close proximity to a maximum surface area of the heat generating component. The wadding material 18 is configured so that its capillary action operates to move or route liguld from the surface of the cooling system 14 towards the surface of the heat generating component 20.

The cooling system 14 includes a condenser 22 (or evaporator coil) . As the skilled person will appreciate, the condenser 22 forms part of an overall cooling system, parts of which may he external to the module. The cooling system 14 may include further apparatus such as a primary coolant fluid (for example, air conditioning fluid) which circulates through the condenser via an inlet 48 and outlet 50, pumps, and storage tanks. Some of these apparatus are not shown in Figure 1.

-24 -Both the cooling system 14 and the heat generating component 20 are substantially planar (that is, having a width and length much larger then their depth) -The cooling system 14 and the heat generating component 20 are arranged substantially vertically. For example, in Figure 1 the plane of the heat generating component 20 and the cooling system 14 are each aligned upright, approximately perpendioular to the base of the cooling system 14.

The cooling system 14 is configured such that its axis of elongation (the longest dimension of the plane) is aligned with the axis of elongation of the heat generating component 20. In figure 1, the planar face of the cooling system 14 is arranged to face or be opposite to the planar face of a heat generating component (in this case, a circuit board) so that their longest sides align. In this configuration the surface area of the faces of the cooling system 14 and heat generating component 20 which oppose each other are maximised.

A vapour gap resides above the heat generating component and wadding in the uppermost portion of the container, and above the majority of the operational portion of the cooling system. Due to stratification, any excess air and moisture will accumulate in the vapour gap. Consequently, the orientation shown in Figure 1 limits the reduction in cooling performance that can otherwise occur when the cooling system is in a region above the heat generating components, within the vapour gap. Beneficially, in the present configuration the air and moisture are not, for the most part, in contact with the cooling system. Ihus, the cooling system is principally in contact with, and acts to cool, the coolant rather than the air vapour.

Figure 1 shows the arrangement of the module when it is suitable for operation. The container 12 contains a coolant.

The volume of the coolant is sufficient for all portions of the wadding 18 to be dampened. The wadding is of sufficient dampness to enable effective cooling. Ihe vapour gap is -25 -retained in the uppermost portion of the container 12, between the surface of the coolant 24 and the upper wall or lid of the container 12.

In the example illustrated in Figure 1, the module includes a secondary cooling system 32. The secondary cooling system forms part of a feedback or secondary circulatory system. Broadly, the secondary cooling system 32 receives excess coolant from the container 12, removes heat from the liquid, and then returns the lower temperature coolant to the container 12.

The secondary cooling system 32 is connected to a feedback outlet 30 of the container, positioned within the vapour gap. The feedback outlet 30 includes a valve 34, for example a pressure release valve. When the valve 34 is open, gaseous coolant will pass through the outlet and be received by the secondary cooling system 32.

The secondary cooling system 32 comprises a secondary condenser 36 and a storage tank 38. The secondary cooling system 32 is arranged so that, in use, the gaseous coolant received by the secondary cooling system 32 will be re-condensed at the secondary condenser 36. Re-condensed coolant is caught, retained and stored within the storage tank 38 before further circulation. Although not shown in Figure 1, the secondary cooling system 32 may include external apparatus necessary for operation, for example pumps and a secondary coolant fluid. The secondary cooling system may be shared with other cooling modules. For example, the secondary cooling system may be connected to more than one feedback outlet from more than one module for cooling a heat generating component.

An outlet of the secondary cooling system (specifically, an outlet from the storage tank) is connected to a feedback inlet 40 of the container 12. The feedback inlet 40 is located in the uppermost portion of the container 12, within the vapour gap. Connected to the feedback inlet 40 is a valve -26 - 44 and a spray nozzle. The secondary cooling system 32, feedback inlet 40, valve 44 and spray nozzle are arranged such that coolant from the secondary cooling system 32 may pass through the feedback inlet 40 and spray nozzle into the container 12. For example, re-condensed coolant within the storage tank 38 may be returned to the container 12. The spray nozzle at the feedback inlet 40 causes liquid to be released in a fine mist or series of droplets.

Advantageously, input of coolant in this form causes less disruption to the flow of the coolant already retained within the ccntainer.

The secondary cooling system 32 of Figure 1 further includes a controller 42. The controller 42 regulates various parameters within the module. In particular, the controller 42 controls one or more valves. For example, in the embodiment of Figure 1 the controller 42 is used to adjust the flow of coolant into the secondary cooling system via the valve 34 at the feedback outlet 30. Furthermore, the controller 42 regulates flow of coolant out of the secondary cooling system 32 and into the container 12 via the valve 44 at the feedback inlet 40.

The controller 42 regulates the flow according to measurements of various parameters by one or more sensors, which are placed within the container 12. The measured parameters may comprise one or more of coolant level, dampness of the wadding material or pressure within the container.

Based on readings from the one or more sensors, the controller 42 determines whether the module is operating at the optimum conditions for efficient cooling. In particular, the controller 42 is configured tc maintain the dampness of the wadding material at its optimum level. Thus, when the wadding is toc dry, the controller 42 allows extra coolant from the reserved coolant contained in the storage tank 38 of the secondary cooling system 32 to enter the container 12 through the feedback inlet 40. If the vapour gap is too large (or the -27 -system is above a desired pressure) the controller 32 may increase the flow of gaseous coolant through the outlet 30 and into the secondary cooling system 32.

The module further comprises an electrical inlet 60 which is positioned in the uppermost portion of the container 12, at a height greater than the heat generating component 20.

Electrical connections 58 to the heat generating component may be fed through the electrical inlet 60. The electrical inlet comprises a seal to avoid leakage of coolant or entry of air or moisture into the container.

Although not shown in Figure 1, a filling inlet is located in the wall of the container 12. The filling inlet allows filling and refilling of the coolant without fully opening the container 12. The filling inlet is located in the top wall or lid of the container 12. In other words, the filling inlet 26 is positioned so that the interior portion of the filling inlet is within the vapour gap in the uppermost portion of the container 12, above the surface of the coolant.

The filling inlet further includes a seal. This is a cap or bung which acts to close the filling inlet.

In use, the module for cooling a heat generating component 10 in Figure 1 includes coolant within the container. The wadding material retains or absorbs the coolant so that the wadding material remains damp. The container 12 is secured and sealed so that it is air-tight.

Operation of the heat generating component 20 causes heat to be transferred to the coolant. A portion of the coolant surrounding the heat generating component 20 increases in temperature, preferably causing a phase change from liquid to gas. As such, said portion of the coolant forms gaseous coolant or coolant vapour. Consequently, the wadding material contains a mixture of coolant in the liquid phase and in the gas phase.

Convection currents are generated within the coolant.

Warmer gaseous coolant (or warmer portions of the coolant) -28 -having a lower density than cooler portions of the coolant will begin to rise. This transfers heat away from the vicinity of the heat generating component 20. The close proximity of the heat generating component 20 to the cooling system 14 results in the convection currents moving the warmer portions of coolant towards the cooling system.

Gaseous coolant in the vicinity of the condenser 22 of Figure 1 will be re-condensed and returned to the liquid phase. By so doing, the cooling system 14 extracts heat from the module.

Re-condensed coolant has a lower temperature and higher density than gaseous coolant. In liquid cooling systems in the prior art, convection currents cause the re-condensed coolant to circulate towards lower portions of the system, by the action of gravity. In contrast, in the module of the present invention, the flow of the convection currents is influenced by the capillary action of the wadding material 18 interposed between the heat generating component 20 and the cooling system 14. In particular, the capillary action of the wadding material 18 routes the lower temperature coolant directly towards the surface of the heat generating component 20.

In the example shown in Figure 1, the capillary action directs the lower temperature coolant crossways from the cooling system 14 to the heat generating component 20. As a result, the capillary action of the wadding material 18 allows low temperature coolant to be distributed more evenly across the complete surfaces of the heat generating component 20, rather than relying on the flow of liquid due to convection currents alone.

The module according to the present invention takes advantage of convective cooling (in particular phase-change cooling techniques) whilst providing a means of manipulating the fluid flow of the coolant for more effective cooling.

Beneficially, the wadding material may be arranged to ensure -29 -homogenous cooling across a complete assembly of heat generating components, or can direct the flow of coolant to specific regicns or components within an assembly of heat generating components. As a result, the appearance of "hot- spots" on a beat generating component or assembly of heat-generating components is reduced. Moreover, the overall efficiency of the cooling system is improved.

Advantageously, inclusion of wadding material with a capillary action acccrding to the present invention may reduce accumulation of lower temperature coolant in the lower regions of the container. This may be observed in the prior art where fluid flow is solely a consequence of convection currents and can result in a temperature gradient between upper and lower regions of the heat generating component. Instead, in the present invention, the capillary action ensures that sufficient lower temperature coolant is directed to components in the upper portion of the container, close to the vapour gap. The configuration of the present invention may be particularly advantageous when the heat generating component is arranged substantially vertically, for example the arrangement shown in Figure 1.

Whilst a preferred embodiment of the present invention and its operating modes have been described above, the skilled person will appreciate that various modifications can be made.

The module is suitable for cooling heat generating components, and especially electrical computer components.

For example, the heat generating component may be a circuit board or mother board, memory modules, central processing units (CPU) or an assembly of electronic computer components.

The container may be any type of container or box that can retain liquid and be made substantially air-tight (that is, does not exhibit significant leakage even when the pressure within the container is above atmospheric pressure) The container may have a lid with a seal which can be opened and closed by the user. Alternatively, the container may be -30 -permanently or semi-permanently sealed after the module is assembled.

As the skilled person would appreciate, the cooling system may be any type of heat exchanger that is arranged to extract heat from the interior of the system. The cooling system preferably includes a condensing system as part of a phase-change cooling system. However, the cooling system may exploit non-phase change cooling. Although the cooling system in Figure 1 is described as planar and having a rectangular surface facing the heat generating component, the skilled person will appreciate that a planar cooling system having an alternative configuration could be used.

The mounting for the heat generating component can be any feature which allows the heat generating component to be affixed within the container. For example, the mounting may be any fixing, feature, slot or indentation within the container that is able to secure the heat generating component.

The wadding material may be any material having a capillary or wicking action, or may be hygroscopic.

Accordingly, the wadding material may be any material which causes liquid to flow without the application of external force or pressure. Furthermore, the capillary action may cause the direction of fluid flow to be in opposition to gravity or another external force. Capillary action results from surface tension and the cohesion of a fluid to the conduit material (in this case, the wadding material) Wadding materials such as cotton wool, paper, cellulose, silica, a metal or a metal oxide (or any combination of said material) may be particularly suitable within the module described herein. However, the skilled person will recognise that various other materials may be used as a wadding material. Ideally, the wadding material is electrically insulating. -31 -

Although preferably the amount of coolant in the container will be sufficient to dampen the wadding, the coolant ievei may alternatively be of a height to result in the heat generating component being part immersed or fully submerged.

A number of types of fluid may be apparent to the skilled person for use as a coolant. Particularly suitable are fluorinated compounds. For example, particularly advantageous may be a perfluroketone or hydrofluroethylene solution.

Beneficially the coolant will be inert and a dielectric or insulator. In order to achieve lower operational temperatures, a coolant may be selected with a freezing point below water. Furthermore, the coolant will ideally have a boiling point at a temperature close to the operational temperature of the heat generating component (before cooling) This will ensure the evaporation of the coolant whilst the component is in use and so permit phase-change cooling.

Although in Figure 1 the feedback outlet of the container is connected to a secondary cooling system, the feedback outlet may instead be connected directly to the exterior or to an alternative system. The valve at the outlet may be a pressure release valve, a manually or electronically controlled valve or any other type of valve providing controlled flow.

In the embodiment of Figure 1, the container has a filling inlet and valve for refilling the coolant. However, alternatively the coolant may be provided within the container during manufacture and permanently sealed. The module is then an entirely enclosed system, and the coolant will not be renewed or refilled by the user. As such, the module may not comprise a secondary cooling system, or any type of secondary circulation system, and be provided without any cutlets or inlets other than the electrical inlet.

The particular embodiment of the invention illustrated in Figure 1 shows an arrangement of the module in which the heat -32 -generating component is substantially planar and arranged substantially vertically. However, the present invention is not limited to this oonfiguration. Alternatively, the heat generating component may be arranged horizontally or at an angle to the base of the container.

Two further embodiments of the present invention are described in detail below. Referring to Figure 2, there is shown a cross-sectional side view of module 210 for cooling a heat generating component. The module 210 includes a container 212 for containing a coolant. The container 212 has a substantially planar cooling system 214 and a substantially planar heat generating component 220. The heat generating component is located spaced apart from the cooling system 214, such that the cooling system can remove heat from the heat generating component 220 via a coolant. A wadding material 218 is disposed within the container 212 so that it is interposed between the heat generating component and cooling system and is in close proximity to a surface of the heat generating component. The wadding material has a capillary action which routes the coolant towards the surface of the heat generating component. The heat generating component and cooling system are arranged such that the planar faces of each element are parallel.

Figure 2 further illustrates a mounting for the heat generating component 216; a condenser 222 as part of the cooling system and having an inlet 248 and an outlet 250; an outlet 230 to the container, having a valve 234; an inlet 240 to the container, having a valve 244 and sprinkler nozzle; and, a pump 252, external to the container 212, for mechanically assisting the circulation of coolant from the lower to the upper regions of the container via pipes 254 and 256.

The heat generating component 220 is shown affixed to a mounting 216. The heat generating component 220 comprises a -33 -planar circuit board, with a number of components attached to the circuit board (for example, memory modules or processors) Electrical connection is made to the heat generating component via wires 258 inserted through a sealed electrical connection inlet 260. The electrical connection inlet 260 is placed in the upper surface or lid of the sealable connector.

The cooling system 214 forms the inner surface of one wall of the container 212. The cooling system 214 comprises a condenser 222 (or evaporation coil) for condensing gaseous coolant. In order to permit circulation of coolant through the condenser 222, the cooling system 214 includes an input 248 and output 250, each further comprising quick disconnect valves.

In use, a coolant is contained within the container 212.

The amount of coolant in the container 212 is sufficient to ensure the wadding 218 is damp and may be saturated, but is not enough to cause components in the container 212 to be fully submerged. Beneficially, smaller volumes of coolant are required compared to systems in which the heat generating component is submerged.

The module 210 further comprises a circulatory system.

In this embodiment, the circulatory system aids the circulating of coolant from the lower to upper portions of the container 212. Coolant may exit from the lower portion of the container at a feedback outlet 230. A mechanical pump 252, external to the container 212, pumps the coolant to a feedback inlet 240 in the upper portion of the container 212 via pipes 254, 256. A control valve 234 is located at the feedback outlet 230 of the container 212. A second control valve 244 is positioned at the feedback inlet 240. The feedback inlet 240 comprises a sprinkler head or nozzle which causes coolant to enter the container 212 as a stream of droplets or spray.

The circulation system provides a secondary mechanism for transfer of coolant, and assists in ensuring the wadding 218 in every portion of the container 212 is kept sufficiently -34 -damp to provide efficient cooling of the heat generating component 220.

The module may further comprise one or more sensors (not shown in Figure 2) . The sensors may be situated on the wall of the container 212, and may be situated at intervals to each other (for example, as differing depths) -The sensors may measure the dampness of the wadding material 218, the coolant level or the internal pressure of the container 212.

This embodiment of the module may comprise a controller (not shown in Figure 2) . The controller may control a number of valves within the module. For example, the controller may control valves 234, 244 at the feedback outlet 230 and feedback inlet 240 of the container 212. The controller may adjust the valves 234, 244 according to measurements of the wadding dampness or the pressure within the container by the one or more sensors described above. In this way, the controller may initiate circulation of coolant from the lower portion of the container to the upper portion of the container 212. For example, the controller may open valves 234, 244 at the feedback outlet 230 and feedback inlet 240, in response to sensors in the upper portion of the container 212 indicating the wadding is insufficiently damp.

In operation, heat generated by the heat generating components 220 is transferred to the nearby coolant retained or absorbed by the adjacent wadding material 218, so causing the nearby coolant to evaporate. Vaporous coolant is then carried via convention currents to the surface of the cooling system. The cooling system 214 and condenser 222 cause the vaporous coolant to re-condense. Subsequently, the lower temperature, re-condensed coolant is routed back to the surface of the heat generating component 220 through the capillary action of the wadding material 218.

The secondary circulation system may be employed to increase circulation of the coolant. This may especially be useful in the event that coolant accumulates in the lower -35 -portion of the container causing the wadding in the upper portion of the container to be too dry. In this circumstance, the valve at the feedback outlet 234 may be opened to allow coolant to he pumped (via mechanical pump 252) to the feedback inlet 240 in the uppermost surface (or lid) of the container 212. When the valve at the feedbaok inlet 240 is opened, coolant will then re-enter the container 212 through the sprinkler nozzle. A spray or jet of droplets of coolant will be released to re-dampen the wadding material 218. The secondary circulatory system may be controlled by a controller, and operate in response to the measured values for dampness of the wadding material 218 or pressure within the container 212.

Referring next to Figure 3, there is shown a further embodiment of a module for cooling a heat generating component. The module 310 comprises a container 312 having a cooling system 314 and enclosing a number of heat generating components 320a, 320b, 32Cc, 320d. In this embodiment, four separate heat generating components 320a, 320b, 320c, 320d are affixed to mountings 316a, 316b, 316c, 316d spaced apart within the container 312. The skilled person will appreciate that although four heat generating components are illustrated in Figure 3, any number of heat generating components could be mounted in this way. The heat generating components 320a, 320b, 32Cc, 320d are planar, and are mounted substantially vertically within the container 312.

The cooling system 314 is located substantially horizontally in the upper portion of the container 312, above the heat generating components 320a, 320b, 32Cc, 320d. In other words, the axis of elongation of the cooling system 314 is positioned perpendicular to the plane of the heat generating components 320a, 32Gb, 32Cc, 32Cd. The cooling system 314 comprises a condenser 322 (or evaporator coil) A wadding material 318 is disposed adjacent the heat generating components 320a, 32Gb, 32Cc, 32Cd. The wadding -36 -material 318 is interposed between the heat generating components 320a, 320b, 32Cc, 320d, so that it Is in close proximity to the surfaces of the heat generating components.

The wadding material 318 has a capillary action, which causes coolant within the module to be routed towards the surface of the heat generating components 320a, 320b, 32Cc, 320d.

Figure 3 illustrates the module having a secondary circulatory system. This system includes a secondary cooling system 332 including a secondary condenser 336 and a storage tank 338. The secondary cooling system 332 is connected to a feedback outlet 330 of the container 312. Flow through the feedback outlet 330 is controlled by a valve 334. The secondary cooling system 332 is further connected to a feedback inlet 340 of the container 312 and the feedback inlet 340 comprises a controllable valve 344.

A controller regulates the flow through controllable valves 334, 344. The controller may regulate the flow according to measurements of the dampness of the wadding material 318, the liquid level, or the pressure with the container 312. These parameters may be monitored by one or more sensors (not shown in Figure 3) which are distributed within the interior of the container 312.

In operation, the heat generating components generate heat causing the coolant at the surface or close to the surface of the heat generating components 320a, 320b, 320c, 320d, to evaporate. Evaporation of the coolant transfers heat away from the surface of the heat generating components 320a, 320b, 32Cc, 320d. The gaseous coolant is transported upwards through the wadding material 318 via convection currents. The gaseous coolant vapour will accumulate at the surface of the cooling system 314 (and oondenser 322) and subsequently re-condense.

Re-condensed coolant, having a greater density than surrounding gaseous coolant, will move downwards onto the wadding 318 and heat generating components 320a, 32Cb, 32Cc, -37 - 320d beneath. Via this mechanism, the wadding material 318 is constantly re-dampened. The capillary action of the wadding material 318 routes the cooler, re-condensed coolant to the surface of the heat generating compcnents 320a, 320b, 320c, 320d and ensures a more uniform distribution of coolant. This in turn results in a more homogenous temperature across the surface of the heat generating components 320a, 320b, 320c, 320d.

In use, the secondary circulatory system allows excess gaseous coolant to be removed from the container 312.

Ideally, the interior of the container 312 is maintained at a pressure which provides efficient recondensation of vaporous coolant. Gaseous coolant may enter the secondary cooling system 332 of the secondary circulatory system through the feedback outlet 330 of the container 312. Vapour within the secondary cooling system 332 may be re-condensed at the secondary condenser 336, and then stored in the storage tank 338 until reguired. The coolant may subseguently be returned to the container 312 through the feedback inlet 340. A controller 342 may regulate the rate of flow through the secondary cooling system 332 via valves 334, 344 at the feedback outlet 330 and inlet 340. The secondary circulatory system provides redundancy in the system, and offers increased capacity for re-condensing the gaseous coolant. Thus, circulation of coolant in the module is increased and the cooling power of the module is improved.

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. Furthermore, method features corresponding to the above-described apparatus features are intended to form part of the invention.

Claims

-38 -CLAIMS: 1. A module for cooling a heat generating component, comprising: a container suitable for containing a coolant, the container having: a cooling system, which is substantially planar; a heat generating component, which is substantially planar, the beat generating component mounted within the container so that the cooling system is spaced apart from the heat generating component and so that the plane of the cooling system and the plane of the heat generating component are substantially parallel, thereby allowing the cooling system to remove heat from the beat generating component via the coolant; and a wadding material, disposed adjacent the heat generating component, the wadding material having a capillary action so as to route coolant towards a surface of the heat generating component.
2. The module according to claim 1, wherein a planar face of the cooling system and a planar face of the heat generating component are facing each other.
3. The module according to claim 1 or claim 2, wherein the wadding is interposed between the cooling system and the heat generating component.

-39 -
4. The module according to claims 1 to 3, wherein the wadding material is in contact with the cooling system.
5. The module according to any preceding claim, wherein the wadding material is arranged such that its capillary action routes coolant from the vicinity of the cooling system toward the surface of the heat generating component.
6. The module according to any preceding claim, wherein the heat generating component is affixed within the container such that, In use, the plane of the heat generating component is substantially vertical.
7. The module according to any preceding claim, wherein the cooling system is positioned within the container such that, in use, the plane of the cooling system is substantially vertical.
8. The module according to any preceding claim, wherein, in use, a vapour space is defined within the container in a region above the heat generating component and wadding.
9. The module according to any preceding claim, wherein, in use, the operational portion of the cooling system is located within the container beneath the vapour space.
10. A module for cooling a pluralIty of heat generating components, comprising: -40 -a container suitable for containing a coolant, the container having: a cooling system; a plurality of heat generating components mounted spaced apart within the container; and a wadding material interposed between the plurality of heat generating components, the wadding material having a capillary action so as to route coolant towards the surfaces of the plurality of heat generating components.
11. The module according to claim 10, wherein the plurality of heat generating components are each substantially planar.
12. The module according to claims 10 or 11, wherein the plurality of heat generating components are affixed within the container such that, in use, the plane of each heat generating component is substantially vertical.
13. The module according to claims 10 to 12, wherein the plurality of heat generating components are affixed within the container such that the plane of each heat generating component is perpendicular to an axis of elongation of the cooling system.
14. The module according to any preceding claim, wherein the heat generating component is an electronic device.

-41 -
15. The moduie according to any preceding claim, wherein the heat generating component comprises one or more electronic devices mounted on the surface of a planar board.
16. The module according to any preceding claim, wherein the cooling system comprises a condenser.
17. The moduie according to any preceding claim, wherein the wadding material is electrically insulating.
18. The module according to any preceding claim, wherein the wadding material comprises one or more of: cotton wool, paper, cellulose, silica, a metal and a metal oxide.
19. The module according to any preceding claim, further comprising the coolant contained within the container.
20. The module according to any preceding claim, wherein the coolant is a dielectric and/or is inert.
21. The module according to any preceding claim, wherein the coolant is a fluorinated compound.
22. The module according to any preceding claim, further comprising: an electrical inlet to the container, through which electrical connections to the heat generating electrical components can be received; a seal at the electrical inlet.

-42 -
23. The module according to claim 22, wherein the electrical inlet is located on a wall of the container at a height greater than the height of the heat generating component.
24. The module according to claim 22 or 23, wherein the electrical inlet is located on a wall of the container at a height greater than the height of the cooling system.
25. The module for according to any preceding claim, further comprising: a filling inlet to the container, through which the coolant can be received into the container; and a seal to the filling inlet.
26. The module according to claim 25, wherein the filling inlet being located on a wall of the container at a height greater than the height of the heat generating component and greater than the height of the cooling system.
27. The module according to claim 25, wherein the filling inlet being located on the wall of the container at a height no higher than the height of the heat generating component within the container.
28. The module according to any preceding claim, further comprising: a feedback outlet from the container.

-43 -
29. The module according to claim 28, further comprising a valve at the feedback outlet.
30. The module according to any preceding claim, further comprising: a feedback inlet to the container.
31. The module according to claim 30, further comprising a valve at the feedback inlet.
32. The module according to claim 30 or 31 dependent on any of claims 28 to 29, further comprising: a secondary circulatory system connected between the feedback cutlet of the container and the feedback inlet of the container, for circulation of coolant.
33. The module according to claim 32, the secondary circulatory system further comprising: a pump; and a storage tank suitable for containing coolant.
34. The module according to claim 32 or 33, the secondary circulatory system further comprising: a secondary cooling system arranged to receive gaseous coolant released through the feedback outlet.
35. The module according to claim 34, the secondary cooling system further comprising: -44 -a secondary condenser arranged to condense gaseous coolant released through the feedback outlet; and a storage tank suitable for containing the condensed coolant.
36. The module according tc claim 35, wherein the secondary cooling system is configured to return coolant condensed within the secondary cooling system to the container through the feedback inlet.
37. The module according to claims 30 to 36, the feedback inlet further comprising: a spray nozzle within the container arranged such that coolant entering the container through the feedback inlet passes through the spray nozzle.
38. The module according to claims 28 to 37, further comprising: a controller to control the flow of coolant into and out of the container at the feedback outlet and/or inlet.
39. The module according to any preceding claim, further comprising one or more sensors for measuring one or more parameters comprising: liquid level; moisture level within the wadding; and pressure within the container.
40. The module according to claim 39 dependent on claim 38, wherein the controller is arranged to adjust the flow of -45 -coolant through the feedback inlet based on the measured parameter from the one or more sensors.
41. The module according to claims 39 or 40, wherein the one or more sensors are capacitive sensors.
42. A method of manufacturing a module for cooling a heat generating component, comprising: providing a container suitable for containing a coolant; housing a substantially planar cooling system within the container; mounting a substantially planar heat generating component within the container, arranged so that the cooling system is spaced apart from the heat generating component and so that the plane of the cooling system and the plane of the heat generating component are substantially parallel, thereby allowing the cooling system to remove beat from the heat generating component via the coolant; providing a wadding material adjacent the heat generating component, the wadding material having a capillary action routing coolant towards a surface of the heat generating component.
43. The method of manufacturing according to claim 42, further comprising: providing a coolant within the container in order to dampen the wadding material.

-46 -
44. The method at manufacturing according to claim 42 or 43, wherein housing the substantially planar coaling system comprises housing the substantially planar coaling system substantially vertically within the container.
45. The method of manufacturing according to claim 42 to 44, wherein mounting the substantially planar heat generating component comprises mounting the substantially planar heat generating component substantially vertically within the container.
46. A method at operating a module tar cooling a heat generating component, comprising: operating a substantially planar heat generating component mounted within a container and being adjacent to a wadding material having a capillary action, the wadding material retaining coolant, whereby operating the heat generating component causes a portion of the coolant to evaporate; condensing the evaporated coolant using a substantially planar cooling system, the cooling system being spaced apart tram the heat generating component, with the plane of the heat generating component and plane of the cooling system being substantially parallel.
47. A method of manufacturing a module for cooling a plurality of heat generating component, comprising: providing a container suitable for containing a coolant; housing a cooling system within the container; -47 -mounting a plurality of heat generating components within the container; providing a wadding material adjacent the plurality of heat generating components, the wadding material having a capillary action which routes coolant towards the surfaces of the plurality of heat generating components.
48. The method of manufacturing according to claim 47, further comprising: providing a coolant within the container in order to dampen the wadding material.
49. A module for cooling a heat generating component, substantially as herein described with respect to figures 1 to 2.
50. A module for cooling a plurality of heat generating components, substantially as herein described with respect to figure 3.
51. A method of manufacturing a module for cooling a heat generating component, substantially as herein described with respect to figures 1 to 2.
52. A method of operating a module for cooling a heat generating component, substantially as herein described with respect to figures 1 to 2.