Heat transfer apparatus

A heat transfer apparatus and method of manufacture is disclosed. The manifold may have a first mechanical interface, a second mechanical interface remote from the first mechanical interface and one or more internal walls defining at least first and second channels within the manifold between the first and second mechanical interfaces. An evaporator member may be attached to the manifold so as to seal the first mechanical interface. A condenser member may be attached to the manifold so as to seal the second mechanical interface. The manifold, evaporator and condenser members may provide a contained heat transfer system in which a working fluid moves between the condenser member and the evaporator member.

FIELD

Example embodiments relate to a heat transfer apparatus and also to a method for forming a heat transfer apparatus.

BACKGROUND

A heat transfer apparatus is used to transfer heat between two solid interfaces. A common form of heat transfer apparatus is the heat pipe. A heat pipe is a contained system that receives heat from an external source at an evaporator portion. The external source may, for example, be an electrical or electronic component. The heat conducts across the wall of the evaporator portion and usually through a thermally-conductive wick structure holding a working fluid in liquid form. The applied heat causes a phase change of the working fluid to vapour. This causes a sharp increase in pressure. The rising vapour moves to another part of the heat pipe at a condenser portion, where it cools. This cooling causes a sharp decrease in pressure, and the pressure differential results in fast transport of heat from the evaporator portion to the condenser portion. Heat is removed to the outside environment. At the condenser portion, the fluid changes phase again and condenses on the walls of the wick which pulls the fluid by capillary action to the evaporator portion again.

SUMMARY

According to one embodiment, there is provided an apparatus, comprising: means for evaporating a working fluid responsive to applied heat; means for condensing evaporated working fluid; and means for connecting the evaporating and condensing means, the connecting means comprising a manifold having a first mechanical interface, a second mechanical interface remote from the first mechanical interface and one or more internal walls defining at least first and second channels within the manifold between the first and second mechanical interfaces, wherein the evaporating means is coupled to the manifold so as to seal the first mechanical interface, the condensing means is coupled to the manifold so as to seal the second mechanical interface, and wherein the manifold, evaporating means and condensing means provide a contained heat transfer system in which a working fluid moves between the condenser member and the evaporator member.

A first wicking means may be provided in the first channel of the manifold, the evaporating means being coupled to a second wicking means, and the condensing means may coupled to a third wicking means, wherein the first wicking means may locate between the second and third wicking means to provide a joined wicking structure for moving working fluid between the second and third wicking means, via the first wicking means, by capillary action.

The first wicking means may comprise a powdered material.

One or both of the second and third wicking means may be grooves or fibres formed on the evaporating and/or condensing means.

The manifold may comprise one or more internal walls defining bifurcated second channels between the evaporating and the condensing means, the bifurcated second channels extending between different respective parts of the second and/or the third wicking means.

The manifold may comprise a plurality of first mechanical interfaces, wherein a plurality of evaporating means are coupled to the manifold so as to seal respective ones of the first mechanical interfaces, each evaporating means having a respective third wicking means, and wherein the one or more internal walls of the manifold define one or more second channels between the plural evaporating means and the condensing means.

The manifold may be formed by additive manufacturing. The manifold may be formed by three-dimensional printing, for example.

The apparatus may comprise a plurality of such manifolds mechanically connected in a three-dimensional structure, wherein a first evaporating or condensing means is mounted on a first such manifold in such a way as to seal, respectively, a first or second mechanical interface of another such manifold when the two are mechanically connected.

The or each evaporating means may be associated with an electrical or electronic component. The or each electrical or electronic component may be supported by at least part of the manifold.

The manifold may comprise a thermally-insulative material.

According to another embodiment, there is provided a method, comprising: forming a manifold having a first mechanical interface, a second mechanical interface remote from the first mechanical interface and one or more internal walls defining at least first and second channels within the manifold between the first and second mechanical interfaces; coupling an evaporating means to the manifold so as to seal the first mechanical interface; and coupling a condensing means to the manifold so as to seal the second mechanical interface, wherein the manifold, evaporating and condensing means provide a contained heat transfer system in which a working fluid moves between the condensing means and the evaporating means.

The method may further comprise providing a first wicking means in the first channel of the manifold, the evaporating and condensing means having respective second and third wicking means coupled thereto, to provide an enclosed heat transfer system in which the first wicking means locates between the second and third wicking means to provide a joined wicking structure for moving working fluid between the interfaces, via the first wicking means, by capillary action.

The manifold may be formed by an additive manufacturing process.

According to another embodiment, there is provided an apparatus, comprising: a manifold having a first mechanical interface, a second mechanical interface remote from the first mechanical interface and one or more internal walls defining at least first and second channels within the manifold between the first and second mechanical interfaces; an evaporator member attached to the manifold so as to seal the first mechanical interface; and a condenser member attached to the manifold so as to seal the second mechanical interface, wherein the manifold, evaporator and condenser members provide a contained heat transfer system in which a working fluid moves between the condenser member and the evaporator member.

A first wick may be provided in the first channel of the manifold, the evaporator member may be coupled to a second wick, and the condenser member may be coupled to a third wick, wherein the first wick locates between the second and third wicks to provide a joined wick structure for moving working fluid between the second and third wicks, via the first wick, by capillary action. The first wick may comprise a powdered material. One or both of the second and third wicks may comprise grooves or fibres formed on the evaporator and/or condenser members. The manifold may comprise one or more internal walls defining bifurcated second channels between the evaporator and the condenser member, the bifurcated second channels extending between different respective parts of the second and/or the third wicks. The manifold may comprise a plurality of first mechanical interfaces, wherein a plurality of evaporator members are attached to the manifold so as to seal respective ones of the first mechanical interfaces, each evaporator member having a respective third wick, and wherein the one or more internal walls of the manifold define one or more second channels between the plural evaporators and the condenser member.

The manifold may be formed by additive manufacturing. The manifold may be formed by three-dimensional printing.

The apparatus may further comprise comprising a plurality of such manifolds mechanically connected in a three-dimensional structure, wherein a first evaporator member is mounted on a first such manifold in such a way as to seal, respectively, a first or second mechanical interface of another such manifold when the two are mechanically connected.

The apparatus may further comprise a plurality of such manifolds mechanically connected in a three-dimensional structure, wherein a first condenser member is mounted on a first such manifold in such a way as to seal, respectively, a first or second mechanical interface of another such manifold when the two are mechanically connected.

The or each evaporator member may be associated with an electrical or electronic component. The or each electrical or electronic component may be supported by at least part of the manifold.

The manifold may comprise a thermally-insulative material.

According to another embodiment, there is provided a method, comprising: forming a manifold having a first mechanical interface, a second mechanical interface remote from the first mechanical interface and one or more internal walls defining at least first and second channels within the manifold between the first and second mechanical interfaces; attaching an evaporator member to the manifold so as to seal the first mechanical interface; and attaching a condenser member to the manifold so as to seal the second mechanical interface, wherein the manifold, evaporator and condenser members provide a contained heat transfer system in which a working fluid moves between the condenser member and the evaporator member.

The method may further comprise providing a first wick material in the first channel of the manifold, the evaporator and condenser members having respective second and third wicks coupled thereto, to provide an enclosed heat transfer system in which the first wick locates between the second and third wicks to provide a joined wick structure for moving working fluid between the interfaces, via the first wick, by capillary action.

The manifold may formed by an additive manufacturing process. The manifold may be formed by three-dimensional printing.

The method may further comprise mounting one or more electrical or electronic components to the evaporator member. The method may further comprise mounting the one or more electrical or electronic components to the evaporator by means of the manifold. The manifold may comprise a thermally-insulative material.

DETAILED DESCRIPTION

Example embodiments relate generally to heat transfer apparatuses, sometimes called heat exchangers. As explained previously, an example form of heat transfer apparatus is a heat pipe which is used to transfer heat between two solid interfaces by means of promoting phase change of a working fluid, e.g. by evaporation from liquid to vapour and then condensation from vapour to liquid. Heat pipes are used in various applications, one of which is the removal of excess or unwanted heat from electrical or electronic components which may otherwise cause damage to, or a drop in performance of, the component or components. Heat pipes are generally located adjacent a heat sink associated with the one or more components mounted on a planar circuit board.

Embodiments herein relate to heat pipes for removing unwanted heat from electrical or electronic components, but the applications of said embodiments are not limited to such.

Example embodiments relate to what may be termed a deconstructed form of heat pipe, that is a heat pipe in which mechanically separate evaporator and condenser members are provided, and are then mechanically attached during manufacture to a manifold which completes an enclosed internal chamber in which the phase changes of a working fluid occurs in use. More than one manifold may be used to complete the enclosed internal chamber. The manifold may comprise one or more walls to define channels within the enclosed internal chamber which form part of a circuit around which the working fluid moves in use.

The manifold may be of any shape and size based on requirements. The manifold may be formed by additive manufacturing (AM), which is a process by which three-dimensional objects are formed layer-upon-layer by depositing material. The material used may be of any suitable type, and additive manufacturing can involve plastics and metals. Three-dimensional printing is a known type of additive manufacturing, in which material is joined or solidified under computer control to create a three-dimensional object. An advantage with additive manufacturing (AM) is the flexibility to create objects of almost any shape or geometry, and the ability to achieve relatively high accuracy. Where thermally insulating materials (i.e. materials with a high thermal resistance) the manifold may act as an insulator in harsh environments or conditions. For example, in cold environments, electronics may be prevented from failure because phase change in the manifold does not occur. Without phase change the electronic component is essentially thermally decoupled from the outside, however, the manifold itself can transfer heat via conduction but this can be mitigated if the manifold is made from an insulating material (<1 W/mK).

FIG. 1Ashows a heat pipe10in cross-section, according to an example embodiment. The heat pipe10comprises a ladder-type manifold20having an upper wall22, a lower wall24and one or more internal walls26which are spaced apart from the upper and lower walls22,24to define channels28. One of said channels29, namely that between the lower wall24and an above internal wall26houses a wick60, hereafter referred to as the manifold wick. Said channel29may hereafter be referred to as a wick channel.

A wick in the context of heat pipes generally is a material or structure that moves working fluid in liquid form by means of capillary action. A wick may comprise a material having pores or grooves suitable for moving the liquid in a given direction. Example constructions include homogeneous or composite constructions, and examples of the former include wrapped screen wicks, sintered metal particles, powder or fibres, grooves and arteries, whereas examples of the latter include composite screens, screen covered grooves and spiral arteries.

Example embodiments use non-conducting powder for the manifold wick60. The powder may be packed, which may involve the powder being loosely packed.

Opposed end faces of the upper and lower walls22,24define first and second mechanical interfaces23,25. The first and second mechanical interfaces23,25are in use connected to, or covered by, separate evaporator and condenser members40,50respectively.

The evaporator member40comprises a generally tray-shaped wall member which is a generally U-shaped in cross-section as shown. Other cross-sections may be used. The wall member may be formed of metal material or one or more other thermally conducting materials. The wall member shown may therefore comprise five walls as will be appreciated. Referring toFIG. 1B, which is a plan view of the evaporator member40in the direction indicated by the arrow41, these five walls may comprise a major wall43, a lower wall44, an upper wall45and two side walls46,47. The major wall43and the lower wall44will be referred to in the following. Referring back toFIG. 1A, within the wall member is provided an associated wick, hereafter referred to as the second wick or evaporator wick42, which may comprise any one of the above wick types other than loose powder. The evaporator wick42is adjacent most or all of the major wall43and most or all of that of the lower wall44, up to the terminating end face of the lower wall.

The condenser member50is similarly constructed, comprising a generally tray-shaped wall member which is a generally U-shaped in cross-section as shown. Other cross-sections may be used. The wall member may be formed of metal material or one or more other thermally conducting materials. The wall member shown may therefore comprise five walls as will be appreciated, similar in form to the plan view ofFIG. 1B. A major wall53and a lower wall54will be referred to in the following. Within the wall member is provided an associated wick, hereafter referred to as the third wick or condenser wick52, which may comprise any one of the above wick types other than loose powder. The condenser wick52is adjacent most or all of the major wall53and most or all of that of the lower wall54, up to the terminating end face of the lower wall.

In other embodiments, the evaporator member40and/or the condenser member50may have different shapes. For example, the part of the evaporator member40that carries the heat source80may be formed of thermally conductive material, the part of the condenser member50where heat is being removed may comprise thermally conductive material, and otherwise the remaining parts may be replaced with other non-thermally conductive material. Therefore, in other embodiments, the evaporator and condenser members40,50may comprise the respective major walls43,53and the remaining walls may comprise part of the manifold20.

The evaporator and condenser members40,50may be formed also by additive manufacturing, e.g. three-dimensional printing.

The arrangement of the manifold first and second mechanical interfaces23,25, and corresponding end-wall interfaces of the evaporator and condenser members40,50is such that, when connected together, a contained space70is defined with a plurality of internal channels28, including the wick channel29. Also, when connected, the manifold wick60locates in-between, and in contact with, the evaporator and condenser wicks42,52to form a joined wick as shown inFIG. 1. A working fluid eg water (not shown) is also provided in the contained space70and space70is under vacuum and free from any non-condensable gases.

FIG. 2shows the heat pipe10in operation. Corresponding reference numerals apply where appropriate. A source80of heat, which may be an electrical or electronic component, a printed circuit board (PCB) or printed wire board (PWB) carrying one or more such components, or a heat sink associated with one or more such components, is shown adjacent the major wall43of the evaporator member40. The heat source80can be any component that generates heat, including motors, turbines etc. The heat source80may be carried on, mounted on or even buried in, the major wall43.

Heat enters the heat pipe10into the evaporator member40and causes the working fluid to evaporate, causing the condensing wick to pull fluid in where evaporation has occurred via capillary action. The resulting vapour84passes through one or more of the channels28defined by the one or more manifold internal walls26, as indicated by the arrows84. The vapour cools as it crosses into the condenser member50and heat is carried away into the outside environment. The vapour condenses into liquid at or in the condenser wick52, whereafter the capillary action of said wick moves the liquid down86and across the manifold wick60to the evaporator wick42whereafter the cycle repeats as further heat enters from the source80.

The structure of theFIGS. 1 and 2embodiment demonstrates the principle of joining decoupled evaporator and condenser members40,50with a manifold20which it will be appreciated can enable a wide range of heat pipe three-dimensional structures and shapes to be formed, e.g. using additive manufacturing. Other example embodiments will now be described, using more complex structures. However, the same principles of operation may apply.

FIG. 3shows another example embodiment heat pipe apparatus100for removing unwanted heat from multiple, in this case first, second and third heat sources102,104,106. The heat sources102,104,106may be electrical or electronic components, printed circuit boards (PCBs) or printed wire boards (PWBs) carrying one or more such components, or heat sinks associated with one or more such components or other heat generating source. The heat sources102,104,106are in this case buried within a more complex three-dimensional manifold arrangement, which is both feasible and useful if the manifold is formed using additive manufacturing or certain other conventional manufacturing methods such as injection moulding, casting, computer numerical control (CNS) machining etc. For example, it enables the heat pipe apparatus100to be mechanically robust and also to occupy a relatively smaller volume because it allows stacking of the heat generating components102,104,106, with separate heat pipes associated with each.

The manifold arrangement comprises a first manifold108comprised of an outer part108A and two inner walls108B,108C which defines a first chamber divided into three channels109A,109B,109C between a first evaporator member110, located alongside the first heat source102, and a separately formed condenser member120located to the other side of the heat pipe apparatus100. The third channel109C comprises a manifold wick115, which may be sintered or not sintered powder as for theFIG. 1embodiment. The manifold wick115is in contact at either end with an evaporator wick122at one part thereof and with a condenser wick124at another part thereof to provide an overall joined wick structure through which a working fluid of the first chamber may circulate and change phase in the manner already described.

The provision of multiple channels109A,109B,109C is useful to prevent bottlenecks occurring in vapour flow. For example, the heat source102may be a PCB or PWB carrying multiple components and therefore producing hotspots. The arrangement of the multiple channels109A,109B,109C allows for this and aims to prevent vapour flow chocking.

The manifold arrangement further comprises a second manifold130comprised of an outer part130A and an inner wall130B, which defines a second chamber divided into two channels between a second evaporator member112, located alongside the second head source104, and the condenser member120. The second channel comprises another manifold wick142which may be sintered powder. The manifold wick142is in contact at either end with an evaporator wick144at one part thereof and another condenser wick146at another part thereof to provide an overall wick structure through which a working fluid of the second chamber may circulate.

The manifold arrangement further comprises a third manifold150comprised in a similar fashion to the second manifold130, having an outer part and an inner wall which defines a third chamber divided into two channels between a third evaporator member114, located alongside the third head source106and the separate condenser member120. The second channel comprises another manifold wick which may be sintered powder. The manifold wick is in contact at either end with an evaporator wick at one part thereof and another condenser wick at another part thereof to provide an overall wick structure through which a working fluid of the third chamber may circulate.

A fourth manifold170may be provided to enclose the first heat source102as shown.

In this manifold arrangement example, the manifolds108,130, and150are coupled to a common condenser member120. It will be appreciated that the condenser member120may comprise multiple separate condenser members. For example, all manifolds108,130,150may be coupled to their own separate condenser members, or some of the manifolds may be coupled to a common condenser member and some manifolds may be coupled to their own condenser member, or a combination of thereof.

It will be appreciated from theFIG. 3example embodiment that we may be able to build customised and complex three-dimensional heat pipes without compromising thermal performance Printed circuit boards or printed wire boards may be stacked into any mechanical shape and move heat to the outside environment with low thermal resistance. The volume of products may have any shape. This may be significant because of the trend to using, for example in radio frequency (RF) communications, increased cell densities and short transmission lengths of next-generation mm-wave transceivers (which may be very close to end-users).

FIG. 4shows another example embodiment heat pipe apparatus180for removing unwanted heat from multiple, in this case first and second, heat sources182,184. Bifurcates channels are employed in this embodiment. The heat sources182,184may be electrical or electronic components, printed circuit boards (PCBs) or printed wire boards (PWBs) carrying one or more such components, or heat sinks associated with one or more such components. The heat sources182,184are in this case carried externally to the side of a complex three-dimensional manifold arrangement, which is both feasible and useful if the manifold is formed using additive manufacturing.

In theFIG. 4heat pipe apparatus180, the first and second heat sources182,184are associated with first and second adjacent evaporator members185,188. The manifold arrangement comprises a manifold190comprised of an outer part190A, and inner walls190B,190C,190D,190E which define a chamber divided into multiple channels. The first evaporator member185, located alongside the first heat source182, is associated with the first channel200A. The second evaporator member188is associated with the second channel200B. First and second evaporator wicks190,192are located alongside both the first and second evaporator members185,188. A separately formed condenser member200is located to the other side of the heat pipe apparatus180. A third channel is shown filled with a manifold wick210, which may or may not be sintered powder as for theFIG. 1embodiment. The manifold wick210in this case is in contact at either end with the first and second evaporator wicks190,192and an intermediate point212thereof is in contact with a condenser wick215. Therefore, in a similar style of operation as previous examples, working fluid is able to move from the condenser wick215through the resulting joined wick structure to the manifold wick210to the first and second evaporator wicks190,192so that the working fluid may circulate and change phase in the manner already described. The manifold wick210may or may not be sintered powder as for theFIG. 1embodiment.

FIG. 5shows another example embodiment heat pipe apparatus200for removing unwanted heat from multiple, in this case first, second and third heat sources202,204,206. The heat sources202,204,206may be electrical or electronic components, printed circuit boards (PCBs) or printed wire boards (PWBs) carrying one or more such components, or heat sinks associated with one or more such components. Other examples of heat sources have been mentioned previously, and embodiments herein are not limited to such. The heat sources202,204,206are in this case carried externally to the side of a three-dimensional manifold arrangement, which may be both feasible and useful if the manifold is formed using additive manufacturing.

The heat pipe apparatus200may be useful for environments where there are large variations in environmental extremes, e.g. between day and night. For example, in an arid environment, it may be beneficial electronics being cooled during the day and insulated from cold at night. The shown heat pipe apparatus200may have a very low thermal resistance when component temperatures are above the phase change temperature of the fluid, e.g. above 40 degrees Celsius. If the component temperature drops below this temperature, then phase change no longer happens and the heat pipe apparatus200has a very high conductive thermal resistance. In other words, the heat pipe may act as a thermal insulator for the electronics, protecting the electronics from electrical failures due to extreme cold. This may make the heat pipe apparatus200useful for scenarios where protection against thermal shock is desired, e.g. in space or on the moon.

The heat pipe apparatus200comprises a manifold210which may be formed using additive manufacturing similar to the previous examples. The manifold210comprises an upper and lower wall and three internal walls, defining four channels. At the interfaces of the manifold210are fixed an evaporator member211and a condenser member212, each having an associated wick216,218. The lower channel of the manifold120houses a manifold wick214in contact with the evaporator and condenser wicks216,218to provide a joined manifold structure so that working fluid may circulate and change phase in the manner already described, and as indicated by the arrows. The manifold wick214may be sintered powder as for theFIG. 1embodiment.

FIG. 6is another example embodiment heat pipe apparatus250, similar in structure to theFIG. 5example, but which employs a hybrid design of heat pipe and gravity driven thermosiphon. Corresponding reference numerals apply where appropriate. In this configuration, the condensed working fluid is returned to the evaporator member211via gravity and not capillary action. When phase change no longer occurs at low component temperatures, there is a higher thermal resistance between the evaporator member211and the condenser member212than the embodiment shown inFIG. 5. The wick216is coupled to the evaporator member211.

Here, as with the other embodiments, there is no convection in a heat pipe apparatus250because it is an evacuated chamber. Radiative heat transfer between the evaporator member211and the condenser member212is reduced by the fact that there is no transverse line of sight between the two. Therefore, conduction is the major heat transfer mechanism coupling the two together. If the manifold210is made out of an insulating material, then the evaporator member211and the condenser member212are thermally decoupled. This may also work for electrical isolation of electrical or electronic components from the outer enclosure which could be of advantage.

A suitable material for the manifold210may comprise a plastics material or similar. For example, the manifold210may be a plastics material. For example, the manifold210may have a thermal conductivity of less than 1 W/mK. For example, the evaporator and condenser members211,212may comprise a more thermally conductive material with a thermal conductivity greater than 1 W/mK. For these evaporator and condenser members211,212, copper is a possible material to use, having a thermal conductivity of 400 W/mK. Alternatively, thermally conductive plastics are available with thermal conductivities of approximately 20 W/mK that may be suitable, for example, if thin-walled.

As mentioned previously, embodiments comprise various parts that can be manufactured in the shown and described forms, which are given merely by way of example, using additive manufacturing.

FIG. 7is a flow diagram showing operations that may comprise a method of manufacture. A first operation7.1may comprise forming a manifold having first and second interfaces defining a plurality of channels between the interfaces. Another operation7.2may comprise attaching a separate evaporator to the manifold to seal the first interface. Another operation7.3may comprise attaching a separate condenser to the manifold to seal the second interface.

FIG. 8is a flow diagram showing operations that may comprise another method of manufacture. A first operation8.1may comprise forming by additive manufacturing, e.g. three-dimensional printing, a manifold having first and second interfaces defining a plurality of channels between interfaces. Another operation8.2may comprise attaching a separate evaporator to the manifold to seal the first interface. Another operation8.3may comprise attaching a separate condenser to the manifold to seal the second interface. Another operation8.4may comprise providing a wick material in the manifold to provide a joined wick structure between wicks of the evaporator and condenser.

The attachment or coupling of the evaporator and condenser members to the manifold may be by means of an adhesive that also provides sealing or mechanically with a separate gasket for sealing and fixing screws

The evaporator and condenser members may also be formed by additive manufacturing.

The manifold may be formed of a thermally-insulative material, so as to thermally decouple the evaporator and condenser members in the absence of phase change of the working fluid.