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(11) | EP 3 124 908 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | APPARATUS AND METHOD FOR EXCHANGING HEAT |
| (57) According to the present disclosure there is provided an apparatus and method for
exchanging heat. The apparatus comprises: a first heat transfer member 101 comprising a slot 101'; a second heat transfer member 102, physically separate from the first heat transfer member 101, wherein the second heat transfer member 102 is movable with respect to the first heat transfer member 101, and wherein at least a part 102' of the second heat transfer member is configured to pass through the slot 101', thereby defining a proximal portion 102" of the second heat transfer member which is within the slot 101' and; a heat exchange region 104 configured to transfer heat between the first heat transfer member 101 and the second heat transfer member 102, the heat exchange region 104 comprising the slot 101' and the proximal portion 102''. |
[0001] Examples of the present disclosure relate to an apparatus and method for exchanging heat. Some examples, though without prejudice to the foregoing, relate to a heat exchanger or heat sink.
BACKGROUND
[0002] Conventional heat exchangers are not always optimal. They may have a narrow operational temperature range and/or low heat transfer capability, i.e. a low heat input to heat output flux ratio. Some heat exchangers use a fluid coolant or refrigerant that may undergo phase transitions, and may have a limited operational temperature range which is dependent on the boiling/condensation temperatures of the fluid used. Moreover such heat exchangers may pose risks in the event of build up of high pressures and rupturing of the sealed vessel containing the fluid thereby releasing the fluid (which may, in some cases, be toxic or hazardous).
[0003] The listing or discussion of any prior-published document or any background in this specification should not necessarily be taken as an acknowledgement that the document or background is part of the state of the art or is common general knowledge. One or more aspects/examples of the present disclosure may or may not address one or more of the background issues.
BRIEF SUMMARY
[0004] According to various but not necessarily all examples of the disclosure there is provided an apparatus comprising an apparatus 100 for exchanging heat comprising:
a first heat transfer member 101 comprising a slot 101';
a second heat transfer member 102, physically separate from the first heat transfer member 101 (i.e. gaps 105), wherein the second heat transfer member 102 is movable with respect to the first heat transfer member 101, and wherein at least a part 102' of the second heat transfer member is configured to pass through the slot 101', thereby defining a proximal portion 102" of the second heat transfer member which is within the slot 101' (at any one point in time) and;
a heat exchange region 104 configured to transfer heat between the first heat transfer member 101 and the second heat transfer member 102, the heat exchange region 104 comprising the slot 101' and the proximal portion 102".
[0005] According to various but not necessarily all examples of the disclosure there is provided a heat exchanger, heat sink, device or module comprising the above apparatus.
[0006] According to various but not necessarily all examples of the disclosure there is provided a method comprising a method for exchanging heat between a first heat transfer member and at least a second heat transfer member, the method comprising causing, at least in part, actions that result in:
passing at least a part of the at least second heat transfer member through at least one slot of the first heat transfer member so as to enable the transfer heat therebetween.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] For a better understanding of various examples of the present disclosure that are useful for understanding the detailed description and certain embodiments of the invention, reference will now be made by way of example only to the accompanying drawings in which:
Figures 1A and 1B schematically illustrate an apparatus according to the present disclosure;
Figure 2 schematically illustrates a further apparatus according to the present disclosure;
Figure 3 schematically illustrates a yet further apparatus according to the present disclosure;
Figure 4 schematically illustrates a yet further apparatus according to the present disclosure;
Figure 5 schematically illustrates a yet further apparatus according to the present disclosure;
Figures 6a and 6B schematically illustrate a yet further apparatus according to the present disclosure;
Figure 7 schematically illustrates a yet further apparatus according to the present disclosure;
Figure 8 schematically illustrates a yet further apparatus according to the present disclosure;
Figure 9 schematically illustrates a method according to the present disclosure;
Figure 10 schematically illustrates a yet further apparatus according to the present disclosure;
Figure 11 schematically illustrates a yet further apparatus according to the present disclosure;
Figure 12 schematically illustrates a yet further apparatus according to the present disclosure; and
Figure 13 schematically illustrates a yet further apparatus according to the present disclosure.
[0008] The Figures are not necessarily to scale. Certain features and views of the figures may be shown schematically or exaggerated in scale in the interest of clarity and conciseness.
DETAILED DESCRIPTION
[0009] Examples of apparatuses and methods for heat exchange according to the present disclosure will now be described with reference to the Figures. The Figures focus on the functional components necessary for describing the operation of the apparatus. Similar reference numerals are used in the Figures to designate similar features where possible/appropriate. For clarity, all reference numerals are not necessarily displayed in all figures.
[0010] Figures 1A and 1B schematically illustrate a block diagram of a cross sectional view and a plan view respectively of an apparatus 100 for exchanging heat.
[0011] The apparatus 100 comprises a first heat transfer member 101 and a second heat transfer member 102 which is physically separate from the first heat transfer member 101. The heat transfer members may be solid thermally conductive members. For example one or more of the heat transfer members may have a thermal conductivity value which can range from a low value of around 0.1 Wm-1K-1 through to high values of 100 Wm-1K-1 or greater.
[0012] The first heat transfer member 101 comprises a slot 101' or aperture. At least a part 102' of the second heat transfer member 102 is configured to pass through the slot 101', thereby defining a proximal portion 102" of the second heat transfer member 102 which is within the slot 101' at any one time.
[0013] The second heat transfer member 102 is movable (see arrow 103) with respect to the first heat transfer member 101. In the example shown, the second heat transfer member 102 has a disc-like form factor and is configured to rotate about a central axis 103' such that the part 102' of the second heat transfer member which is configured to pass through the slot 101' circulates around, thereby altering the portion of the part 102' of the second heat transfer member 102 which is within the slot 101' at any one time. In other examples, other forms of movement of the second heat transfer member with respect to the first heat transfer member are possible. For example, the second heat transfer member may have a tape like form factor and be configured to be fed into and out of a slot/aperture of the first heat transfer medium (as discussed further below with reference to Figures 7 and 8).
[0014] The apparatus comprises a heat exchange region 104 configured to enable the transfer of heat between the first heat transfer member 101 and the second heat transfer member 102. The heat exchange region 104 comprises the slot 101' of the first heat transfer medium and the proximal portion 102" of the second heat transfer medium.
[0015] The proximal portion 102" of the second heat transfer member is configured to be highly proximal to the surface edges of the first heat transfer medium which define the slot 101'. In some example the proximal portion may be in a contactless fit with the first heat transfer medium. In other examples the proximal portion may be in a close/tight but substantially contactless fit with first heat transfer medium, i.e. closely fitting but with sufficient separation to allow low friction passage of the proximal portion through the slot of the first heat transfer medium. The proximal portion within the slot may be separated from the slot by a separation distance/gap 105 of less than one or more of: 1 mm, 0.1 mm, 50µ, 25µ, 10µ and 5µ on each side of the proximal portion. For example, for a proximal portion having a thickness t, which is centrally disposed within a slot of width w, the effective gap (on either side of the proximal portion) g = (w-t)/2. The separation distance/gap may depend upon a number of factors, including the size of the apparatus and the desired throughput power. For example, up to 1 kW the separation distance/gap may generally be kept below about 30µ while for greater power and larger apparatuses, a separation distance/gap of up to 0.25mm could be acceptable. The separation distance/gap may also be dependent upon the working medium (air, He. H2 etc. between the heat transfer members)
[0016] The thickness 110 of the portion 201' of the second heat transfer member which passes through the slot may be less than one or more of: 5mm, 1 mm, 0.1 mm, 50µ and 5µ. There are a number of design considerations that may be taken into account when determining the thickness of the portion 201' of the second heat transfer which may depend upon the application, temperature range and power throughput desired. A small apparatus having a heat throughput below about 1 kW could operate with the second heat transfer member 102 at a thickness of 75 to 100µ (and a gap of the order of 15µ) but high powers may well utilise a second heat transfer member 102 of a thicknesses of several millimetres. The thermal resistance of such a relatively thin heat member may help to keep a thermal time constant down and thus increase the potential throughput for a given mass of apparatus. Such a thin second heat transfer member may provide increased thermal transfer per unit mass as compared to a thick heat transfer member. In some examples, the ratio of the thickness 110 of the second heat transfer medium and the gap is of the order of 5:1.
[0017] In some examples, the proximal portion 102" is sufficiently proximal to, yet substantially in non-physical contact with, the first heat transfer member such that primary mechanism of heat transfer therebetween is substantially conduction (as opposed to convection, radiation or diffusion). Other examples, may a) rely on augmentation of the conductive heat transfer by e.g. convective heat transfer, and b) rely on radiative heat transfer alone. In certain examples, there may be contact between the moving and stationary heat transfer members, however, the friction may be kept at sufficiently low levels such that the impact on overall performance is small.
[0018] The two heat transfer members may effectively be in thermal contact with one another but not in physical contact with one another, or at least substantially not in contact with one another. Ideally the contact between the moving and stationary heat transfer members would be zero, but practically this may not be feasible and some contact may occur. Significant physical contact would give rise to undesirable frictional heating when the two heat transfer members move with respect to one another. The transfer of heat between the two substantially non-physically touching heat transfer members may occur via conduction, i.e. vibrating atoms and molecules of the first heat transfer member interact with neighbouring atoms and molecules of air in the air gap 105 thereby transferring some of their energy/ heat to the neighbouring particles in the air gap. The vibrating particles in the air gap themselves then interact with neighbouring atoms and molecules in the proximal portion 102" of the second heat exchange member thereby transferring some of their energy/heat to the second heat exchange member.
[0019] The second heat transfer member 102 is movable with respect to the first heat transfer member 101. A motor, prime mover or other movement means may be used to move the heat transfer members with respect to one another. Such movement alters the portion of the second heat transfer member which is substantially contactlessly within the slot at any one time, i.e. the part of second heat transfer member which defines the proximal portion changes with movement of the second heat transfer member. The rate of movement may be dependent upon the thermal time constants for the material within the slot and the thermal time constant of the material outside of the slot. The rate of movement may be determined based on design factors such as "in-slot" and "out of slot" thermal time constants which are in turn dependent upon thermal resistances and material thermal capacities.
[0020] In various examples, the first and second heat transfer members are made of solid materials. In effect the second heat transfer member acts as a kind of solid coolant/working medium (as opposed to a fluid coolant/working medium as per typical previous systems) which picks up heat at one point in its movement and dissipates the heat in another point in its movement. For example, the apparatus may act as a heat sink wherein the second heat transfer medium picks up heat when inside the slot and dissipates the heat when outside of the slot. Alternatively, the apparatus may act as a heater to provide heat to the first heat transfer member, wherein the second heat transfer medium picks up heat when outside of the slot and dissipates the heat when inside the slot.
[0021] An example of operation of the apparatus 100 will now be described, with apparatus operating as a heat sink to cool/remove heat from the first heat transfer member.
[0022] Heat (QIN) 106 may be input at a distal region 101" of the first heat transfer member 101, for example via thermal contact with an object to be cooled such as a processor or chip. The first heat transfer member may be thermally conductive such that the input heat is conducted to the surfaces of the first heat transfer member which surround and define the slot 102'. The second heat transfer member may absorb heat from the first heat transfer member at its proximal portion. However, when the second heat transfer member moves with respect to the first heat transfer member, the (heated) portion of the second heat transfer member within the slot moves outside of the slot whereupon it can start to dissipate the heat out (QOUT) 107 (e.g. via convection) to an ultimate heat sink, e.g. the air/atmosphere.
[0023] The portion of the second heat transfer member outside of the slot 102' / outside of the heat exchange region 104 provides a region 102'" in which heat dissipation may occur. The region 102'" of the second heat transfer medium outside of the slot may be greater than: 25%, 50%, 75%, 90%, 100%, 200%, 300%, 400% or 500% larger than an area of proximal portion 102'' of the second heat transfer medium within the slot. Since heat transfer occurs within the heat exchange region 104 via the relatively low thermal impedance process of conduction, the area of the second heat transfer member within the heat exchange region, i.e. the area of the proximal portion 102") may be smaller than the area of the second heat transfer member outside of the heat exchange region, i.e. the area of the region 102"', where heat may dissipate out via the less efficient process of convection. The relative sizes of the "in-slot" 102" and "out of slot" 102'" regions may depend upon a number of factors, and generally may be designed to make the thermal time constants "in-slot" and "out of slot" to be approximately equal. Thus the relative sizes of the "in-slot" and "out-slot" regions might range from say 10% up to greater than 90% depending upon the application. As an example, a "back to back" heat exchanger which allows the transfer of heat from an hermetically sealed vessel to ambient air might have a value of "in-slot" size to "out of slot" size of around 50%. However, transfer from such an hermetic sealed apparatus might have an "in-slot" region of greater than 90% of the "out of slot" region if the external ambient medium was liquid water rather than air.
[0024] Having a large "out of slot" region 102'" provides a large surface area for heat transfer output via convection, e.g. natural convection (fanless). However, in some examples, to aid heat dissipation and enhance convective cooling a fan 108 may optionally be provided to blow air 109 (or other fluid) over the region 102"', namely the exposed surface of the second heat transfer member not within the slot 102' / outside of the heat exchange region 104. Upon further movement, the portion of the second heat transfer member may be moved (rotated in this case) back into the heat exchange region and brought back into the slot and close proximity with the first heat transfer member to absorb further heat. This cycle may be repeated.
[0025] When operating as a heater, portions of the second heat transfer member outside of the heat exchange region may absorb heat before moving (rotating) into the heat exchange region/slot wherein the second heat transfer member may transfer heat to the first heat transfer member. After passing through the heat exchange region/slot, portions of the second heat transfer member outside of the heat exchange region/slot may absorb further heat before rotating round again and being 'circulated' / passed back through the heat exchange region to transfer further heat to the first heat transfer member.
[0026] In either case, the second heat transfer member acts akin to a solid coolant / working medium which circulates in a loop through the heat exchange region. Heat energy is absorbed (e.g. via conduction) at one point in the cycle (e.g. inside the heat exchange region) and released/given up (e.g. via convention) at another point in the cycle (e.g. outside of the heat exchange region).
[0027] Without limiting the scope of the claims, an advantage/technical effect of some examples of the present disclosure may be to provide enhanced thermal transfer throughput (i.e. in terms of throughput or surface heat flux or axial heat flux) and an increased operational temperature range. Examples of the present invention do not rely on phase transitions and thus are not restricted to operational temperature ranges limited to boiling and condensation temperatures of a working fluid, e.g. coolant or refrigerant, nor is there a risk of the working fluid freezing or boiling and creating excessively large pressures at extreme temperatures. Thus examples of the present invention may be better able to withstand such temperature extremes and provide safe operation and avoids the risk of leaking of the working fluid, which could damage surrounding components (and also potentially endanger nearby personnel), especially when used as a heat sink for processors/electronics.
[0028] Figure 2 schematically illustrates a partial cross sectional view of another apparatus 200 according to the present disclosure. The apparatus 200 is similar to the apparatus 100 except that a plurality of second heat transfer members 102a-102d (each separated by a separation distance 210) and a plurality of slots 101'a - 101'd are provided in the heat transfer region 104. Several thin heat transfer members can be used for the same mass as single thick heat transfer member which can provide significantly increased surface area and heat exchange properties than a single thick heat transfer member. Apparatuses according to the present disclosure can be scaled so as to provide additional heat transfer members and slots to increase thermal transfer throughput. Although only 4 slots and 4 second heat transfer members are shown, in some examples more than 10, 50, 100 and 500 second heat transfer members and slots may be provided. The number of slots and moving heat transfer members may depend upon a number of factors, not the least of which is the particular application being considered. A cryogenic surgery probe may only have one or two moving members and associated slots, whereas an industrial air conditioning plant heat exchanger might have several hundred.
[0029] Stacked platters/leaves of second heat transfer members may be separated by spacers (not shown) to maintain appropriate alignment with the slots.
[0030] The plurality of second heat transfer members may be 3 dimensionally shaped so as to stack on top of one another and nest against one another to provide a self-supporting spaced apart portions that pass through the slot. For example, the second heat transfer members may be 3 dimensionally shaped akin to a trumpet end shape, each having a tapered central portion and a flange/circumferential perimeter portion, configured so that, when nested/stacked together the flange/circumferential perimeter portions are automatically appropriately spaced apart from each and in alignment with the slots of the first heat transfer member).
[0031] The plurality of second heat transfer members 102a-102d may be configured to be parallel to one another having a uniform separation distance as in the apparatus 200 of figure 2, or may be configured in a splayed configuration (as exaggeratedly shown in the apparatus 300 of Figure 3 for effect). A splayed configuration may allow easier matching of fan characteristics to the airflow impedance of the moving members "out of slot".
[0032] In the apparatus 300 of Figure 3, a separation distance 310 between adjacent second heat transfer members of the plurality of second heat transfer members 102a-102c varies along the length of the adjacent second heat transfer members. For example the plurality of second heat transfer members 102a-102c may be are splayed / gradually spread out from one another such that their separation distance 310 increases to a larger separation distance 310'. The heat transfer coefficient may reduce as the spacing of the heat transfer members 102 increases, but lower airflow impedance will also result.
[0033] In the above examples, a single second heat transfer member is provided with its own individual slot. However, in some examples more than one second heat transfer member may be provided in each slot.
[0034] Figure 4 schematically shows an apparatus 400 in which more than 1 second heat transfer members 102a, 102b (each separated by a separation distance 410) are disposed within a slot 101'. The use of plural second heat transfer members per slot may help improve the apparatus's tolerance to dirt/dust. The use of plural second heat transfer members per slot may also provide a large increase in heat transfer area in the "out of slot" convective heat transfer region. For example, two heat transfer members per slot may double the surface area for convective heat transfer, while maintaining the same heat transfer area for conductive transfer into heat transfer member 102.
[0035] Figure 5 schematically shows an apparatus 500 comprising a plurality of second heat transfer members in the form of rotatable thin discs/platters 102a-102d, configured to pass closely through plurality of narrow slots 101 'a-101'd. The apparatus also comprises a fan 508, which may be provided integrally with the discs. Here the fan is a centrifugal air blower that is coaxially aligned with central axis of rotation of the plurality of second heat transfer members 102a-102d. the centrifugal fan receives air 109 axially inwards and blows it radially outwards 510 between the layers of the plurality of second heat transfer members. Instead of using an air blast to enhance the heat dissipation, in other examples a different fluid may be used. For example, the apparatus may be housed in an hermetically sealed enclosure containing a fluid, for example: Hydrogen, Helium, a liquid or even a cryogenic fluid.
[0036] The second heat transfer member(s) need not be of a circular shape but could instead be of another shape, not least for example:
a substantially planar/flat substantially 2D shape
a disc like shape (e.g. a platter of a thin foil or film)
a ring like shape such as a torus
a curved 3D shape
a frustoconical or cone shape
a trumpet shape (conical but flaring at the broad end)
an elongate shape, such as a tape, ribbon or strip of a flexible material (as in Figures 7 and 8)
[0037] The second heat transfer member may be a solid material which may be rigid/self supporting. It could be made of a thermally conductive material such as a metal not least for example Aluminium or Copper. However, in some examples it could be one or more of: a non-metallic material, a plastic material, a polymer, a flexible material. The ability to use a plastic material, e.g. PET, advantageously may enable a reduction in the mass of the apparatus and also an improved mass/heat transfer ratio of the device as well as enable the use of low cost materials. The material may be selected so as to have optimal properties for the intended use, e.g. a material having a high density and a large specific heat capacity so that it is able to absorb as much heat in as small a space as possible.
[0038] Figures 6A and 6B schematically illustrate a yet further apparatus 600, similar to the apparatus 500 of figure 5 but with the addition of a second plurality of second heat transfer members 602a-602d configured to interleave with the plurality of second heat transfer members 102a-102d in a second heat exchange region 604. The second plurality of second heat transfer members may move with respect to the first plurality of second heat transfer members, as shown with arrow 603. The first plurality of second heat transfer members 102a-102d may be configured to have a small peripheral region 102' that interleaves the first heat transfer medium 102, whilst the second plurality of second heat transfer members 602a-602d may be configured to have a larger region 602" that interleaves the first plurality of second heat transfer members 102a-102d. Such an interleaving/cascading arrangement of moving members 102a-102d and 602a-602d may provide a simple geometric means to optimally utilise available materials and space.
[0039] A further series of such cascading units (not shown) could be provided, which further increases the operational temperature range of the apparatus, wherein the configuration and materials of each unit could be optimised for its respective operational temperature range. For example, a high melting point material could be selected for the first (primary) set of plurality of second heat transfer members 102a-102d, whereas a material of a lower melting point could be selected for the second (secondary) set of plurality of second heat transfer members 602a-602d.
[0040] The second heat transfer members may also be provided with slots/apertures 611. These slots/apertures may be provided in a peripheral region and be configured to relieve stress within each second heat transfer member, particularly during motion thereof, which may increase the apparatus' tolerance and durability.
[0041] In the above described apparatuses of figures 1 - 6, the movement of the first heat transfer medium with respect to the second heat transfer medium is due to rotation of a part 102' of the second heat transfer medium through a slot/aperture 101' of the first heat transfer medium. In contrast to such 'rotational' apparatuses, figures 7 and 8 schematically illustrate apparatuses having an alternative form of motion with respect to one another, referred to herein as `linear' apparatuses.
[0042] In the apparatus 700 of Figure 7, the whole of the second heat transfer medium 702 passes through a slot/aperture 101' of the first heat transfer medium. The second heat transfer medium comprises an elongate thin tape-like member which is passed through the slot/aperture via appropriate movement means, e.g. a configuration of supports and rollers 711, 712 that conveys the strip-like second heat transfer medium into the slot 101', thereby bringing the second heat transfer medium into close, but substantially contact-free, proximity with the slot within the heat exchange region 104. A gap 105 between the second heat transfer medium and the first heat transfer medium is provided which is sufficiently small such that the primary heat transfer mechanism in the heat exchange region is conduction.
[0043] The movement means moves the second heat transfer medium (see arrows 703 and 703') such that the second heat transfer medium circulates around into and out of the heat exchange region 104.
[0044] Figure 8 schematically illustrates a further `linear' apparatus 800 which shows that various of the above described features of the 'rotational' apparatuses could equally well be applied to the `linear' apparatuses. For example, the linear apparatus 800 may comprise:
a plurality of slots 101'a-101'c,
a first plurality of second heat transfer mediums 702a-702c and
a second plurality of second heat transfer mediums 802a-802b which may be interleaved with the first plurality of second heat transfer mediums (shown here interleaving in a second heat exchange region 804 in a crosswise manner), in effect so as to form a cascade of heat transfer devices to increase the effective area for convective heat transfer.
[0045] The plurality of second heat transfer mediums may also be splayed similar to that of Figure 3 (not shown in Figure 8).
[0046] Various examples of the above described apparatuses (both the rotational and linear versions) may take the form of: a heat exchanger, a heat sink, a heat pump, or a module and each of these may be comprised in a device. As used here 'module' refers to a unit or apparatus that excludes certain parts/components that would be added by an end manufacturer or a user.
[0047] The apparatus may be configured for use in heat pump and refrigeration applications and provide the potential for a solid material to be used both as the thermodynamic element (whether magnetocaloric or electrocaloric) and also act as the main heat transfer element to ambient air.
[0048] Figure 9 schematically illustrates a method 900 for exchanging heat between a first heat transfer member and at least a second heat transfer member according to an example of the present disclosure. The method comprises, in block 901, passing at least a part of the at least second heat transfer member through at least one slot of the first heat transfer member so as to enable the transfer of heat therebetween.
[0049] The at least a part of the at least second heat transfer member may be passed sufficiently proximal to, yet still in non-contact with, the at least one slot of the first heat transfer member such that the primary mechanism for heat transfer between the two heat transfer members is via conduction.
[0050] Examples of the present disclosure provide both a method and corresponding apparatus comprising various means or modules that provide the functionality for performing the actions of the method.
[0051] In the "linear" form a ribbon or tape of material is moved through a gap with small clearance. Heat may be added or removed by the tape depending upon the application and on the position in an heat transfer device. Typically, the tape or several tapes in parallel will move through a slot or parallel array of slots. The slots are part of either a source or a sink and thus heat may be transferred to, or from, the tape. This second region may, or may not be an array of fins as for the source or sink at the first region. It may alternatively be simply a region of air blast cooling, where air is passed over the bare tape to transfer heat from or to the tape. It should be noted that the tape does not have to touch any of the extended/fin surfaces and thus friction can be extremely low as can wear resulting from such contact. However, it is expected that such contact may occur but that it will be minimal if the device is constructed carefully.
[0052] The combination of a high "effective" heat transfer coefficient as a result of the gap's equivalent thermal resistance, together with the surface area augmentation resulting from surface finning, allows very high thermal flux levels to be obtained.
[0053] The material from which the fins are constructed should be of high thermal conductivity to allow large ratios of fin height to base dimension to be achieved. Materials such as copper, silver, graphite or diamond composite may typically be considered. However, the use of thin heat pipes may also be used as "fins". The material from which the tape is made can be almost any solid material. The thinner the tape becomes, the less important the thermal conductivity of the material. Polymeric materials such as PET or PTFE or POM, etc. may all be advantageously used for the construction of the tape as long as the operating temperature of the device fits within the operational limits of the material used. Thus PET might be used between cryogenic temperatures and approximately 120C while PEEK polymer may be used beyond 200C. Stainless steel tape could be used to beyond 600C. Stainless steel has particularly advantageous material properties in terms of the product of its specific heat and density (cp*ρ). The "residence" time of the ribbon's engagement with the finning may be adjusted to ensure that adequate take up of thermal energy takes place, while at the same time affording a high enough temperature rise such that this heat may be dissipated effectively to the ambient air in the non-engaged section.
[0054] The same general principles apply to the "rotary" form of the technology. In some "rotary" examples these may be provided a parallel stack of discs of thin material which rotate about a common axis. One distinct angular region of the discs engages with narrow slots formed in a block of thermally conductive material, e.g., aluminium or copper. The block may be cut from a solid or formed from a stack of thin sheets of thermally conductive material. This stack of sheets is held together by an outer frame. Each thin disc engages with the slots formed in the conductive material for a fraction of the full 360 degrees. Typically the engagement arc is of the order of 10 to 90 degrees. During the rest of the period of rotation when the thin disc is not in engagement, there is formed a gap between the discs through which air or other gaseous media may be passed.
[0055] There are a number of features which improve either the construction/assembly of the device or allow for further exploitation of the device. These include:
Two "leaves" per slot - this improvement may help to increase the tolerance of the system, rotary or linear, to either variations in gap width or leaf/ribbon thickness, or to the system's ability to cope with the ingress of dirt or dust particles. It may also double the surface area available for heat transfer in the convective region of the device. Generally, the overall flux and throughput capability of the devices constructed with this feature will be reduced but there are situations where the additional tolerance is worth having. Such a reduction may be due to the fact that there could be a reduction in mass transport through the slot simply because of the addition of an additional gap between the two moving members 102a and 102b.
[0056] "Splayed" linear or rotary layout. Here, the thin discs or ribbons are forced apart from one another as they exit the slots and are forced together as they enter the slots. This allows very high flux levels at the engagement region while allowing increased air passage side over the non-engaged portion of travel to ensure low pressure drop air flow.
[0057] "Cascaded" layout of either linear or rotary form (e.g. as per figures 6A and 6B). With such feature, the ratio of input to output fluxes may be considerably increased by engaging one or more sets of thin discs or ribbons with one another. This form has the added advantage over the single disc stack in that much better utilisation of the available material may also be achieved, particularly for the case of the rotary forms of the device.
[0058] "Sealed Hydrogen or Helium based devices". The thermal conductivities or Hydrogen and Helium are several times higher than that of air, this allows for much higher heat fluxes to be achieved but does require a sealed vessel for the device, to maintain the Hydrogen or Helium atmosphere between the slot gaps and the thin discs or ribbons of material. In this instance the advantage over heat pipes, of having a relatively open structure, is lost. However, at cryogenic temperatures, the flux capability of the new technology may be considerably better (two or more times greater) than heat pipe alternatives.
[0059] Toxic or exotic materials can be excluded from the design over a very wide operating temperature range. Various examples of the apparatus may allow heat transfer both for cooling or heating an can provide considerable performance improvements in terms of thermal flux over existing methods, particularly at cryogenic temperatures.
[0060] In the rotary example, a parallel array of thin discs mounted on a common shaft are rotated about the common axis, i.e., as per figure 5. The discs engage for approximately 10% to 90% of their travel, with a stationary array of thermally conductive plates or fins. The precise percentage of the thin discs' perimeter engaged with the stationary plates is determined by a number of operating parameters, such as the size of the heat sources and the space available for the heat transfer mechanism, etc. The thin discs are separated from one another on the central shaft by spacers to allow precise matching of the disc positions with the lost positions formed by the stationary plates. The spacing of the stationary plates is produced either by precision machining or by a precision assembly made from a stack of plates and spacers. The slot width is intended to be only slightly larger than the thickness of the thin rotating discs. A typical value of the "gap" resulting from the thin disc in the slot may be around 25 microns for a small (<1KW) device. Plate material thicknesses can be readily achieved with a tolerance of plus and minus 5 microns over about 300 mm+ dimension on a mean thickness of 100µ. A similar tolerance can be obtained for the material of the thin rotating discs. Nevertheless, for large stacks of thin discs and thin plates, it may be desirable to make some allowance for a build up of tolerances. This tolerance allowance may be produced by one or more features. The spacers between the thin rotating discs may be flexible; the thin discs themselves may have slotted sections which allow for flexibility of the disc as it rotates; additional spacers may be added to the thin disc pack as the assembly is made. An alternative to the large number of spacers and "tolerance allowance adjusters" might be that the thin discs are stackable with inner flexible members which are locked in place by, e.g., welding or adhesive bonding on completion of the assembly. The thin discs are allowed to find their own optimum position relative to the central shaft and are then fixed in place by one or other means (laser, ultrasonic or adhesive bonding).
[0061] On a particular example of the disclosure suited to, but not limited to, processor cooling is a stack of circular discs with a central hole which is rotated by some means at the base of the device. The means of rotation may be by a reduction geared electric motor, or by stepper motor type drive or by piezoelectric drive or by harmonic drive operating off the fan shaft. Typically for this size of application (100 to 1000[W]), the stack of discs will be rotating at around 50 rpm while the fan shaft will be turning at about 5000 rpm. A typical value for the circular disc thickness would be 75 microns in polyethyleneteraphthlate (PET), a very common polymer used extensively for packaging and food containers. However, many other polymers may also be used. Polyoxymethylene (POM), also known as acetal, has a particularly attractive (density x specific heat) product. Low, medium or high density polyethylene may also be used if the operating temperature is kept low and cost is a major factor. Multilayer or composite foils or films may be used to advantage where particular characteristics of the rotating discs have to be provided, such as flexibility, or robustness to dirt ingress.
[0062] Inside the central hole a fan may be mounted to provide air flow through the discs or foil or film, thus providing an integrated fan heat exchanger apparatus.
[0063] The discs are rotated through a series of slots in an offset stack of aluminium sheets which are connected to the processor chip or other load. The aluminium stack occupies typically 20% of the perimeter of the foil or film discs. The remaining 80% is available for air blast cooling.
[0064] This particular example has so far been described as an open device operating in air, with the thermal resistance between foils or films and slots being calculated based on air as the conductive medium. However, vastly improved performance may be obtained if the foils or films and slots are operated in either a Helium or Hydrogen environment. This would require the apparatus to be sealed to maintain the presence of the gases in the slot gap.
[0065] The short list below gives some indication of the diversity of applications of examples of the present disclosure:
Cooling of computer processor chips;
Cooling of power semiconductors;
Cooling of photovoltaic solar collectors - particularly concentrated systems;
Solar furnace heat transfer for power generation - the new technology provides an alternative to molten salt systems;
Compact heat exchangers for nuclear power generation;
Temperature control in industrial process plant by heat transfer either heating or cooling action;
Spacecraft/satellite temperature control;
Cryogenic surgery applications where examples of the apparatus may offer superior performance to existing systems in terms of both temperature control and surface flux capacity;
Compact heat exchangers for compressed gas cooling on maritime gas platforms/rigs where space is at a premium
[0066] The above applications are mainly for cooling heat transfer, however, examples of the disclosure may be used for either heating or cooling applications.
[0067] Features described in the preceding description may be used in combinations other than the combinations explicitly described. Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. Although features have been described with reference to certain examples, those features may also be present in other examples whether described or not. Although various examples of the present disclosure have been described in the preceding paragraphs, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as set out in the claims. For example, although an air gap is disclosed, in some examples other working fluids could be used. For example, one or more parts of the apparatus could be housed in a hermetically sealed enclosure containing another fluid, for example Hydrogen or Helium. Also, although example apparatuses have primarily been discussed operating as a heat sink whereby heat input to the first heat transfer member is output and dissipated via the second heat transfer member, it is to be appreciated that apparatuses could operated in the opposite manner whereby heat is transferred from the second heat transfer member to the first heat transfer member.
[0068] The term 'comprise' is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use 'comprise' with an exclusive meaning then it will be made clear in the context by referring to "comprising only one ..." or by using "consisting".
[0069] Figure 10 schematically illustrates a yet further apparatus 1000 for effecting heat transfer between two environments that are kept separate by a physical wall. A first side of a first heat transfer member 1001 interleaves and inter-engages with a first set of second heat transfer members 102a-d disposed on a first side of a hermetic barrier (which defines a first environment). A second side of the first heat transfer member interleaves and inter-engages with a second set of second heat transfer members 1002a-d disposed on a second side of a hermetic barrier 1010 (defining a second environment). The first heat transfer member is configured such that its first side is located on the first side of the hermetic barrier and its second side is located on the second side of the hermetic barrier. This example provides the advantage that a small mass/amount of thermally conductive medium may be required for the first heat transfer medium 1001 whilst the sets of second heat transfer members 102a-d and 1002a-d may be made from low cost, low mass materials, not least for example polymeric sheets/discs. It will be appreciated that a linear version of the rotary version shown in figure 10 may also be possible.
[0070] Figure 1 schematically illustrate rotary version of an apparatus 1100 in which a plurality of first heat transfer members 1101a-c are provided, e.g. around a periphery of the second heat transfer member 1102. Such an arrangement may provide multiple conducting inputs QIN1 - QIN3 and a single convective output QOUT.
[0071] Figure 12 schematically illustrates a linear version of an apparatus 1201 comprising multiple convective inputs QIN and a single slotted conductive output QOUT.
[0072] Figure 13 schematically illustrate a rotary version of an apparatus 1300 comprising a conductive inputs QIN and a conductive output QOUT. The conductive input(s) and output(s) may be hermetically sealed from one another. The input and output flux levels may be the same or the apparatus may be configured to provide large ratios between the input and output fluxes and a wide operating temperature may be provided.
[0073] It will be appreciated that the apparatuses may be configured to provide multiple heat sources and multiple sinks. For examples the apparatus may be configured to provide:
one or more conductive input(s) and one or more convective output(s);
one or more convective input(s) and one or more convective output(s);
one or more conductive input(s) and one or more conductive output(s); and
one or more convective input(s) and one or more conductive output(s).
[0074] In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term 'example' or 'for example' or 'may' in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some or all other examples. Thus 'example', 'for example' or 'may' refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all of the instances in the class.
[0075] In this description, references to "a/an/the" [feature, element, component, means ...] are to be interpreted as "at least one" [feature, element, component, means ...] unless explicitly stated otherwise.
[0076] The above description describes some examples of the present disclosure however those of ordinary skill in the art will be aware of possible alternative structures and method features which offer equivalent functionality to the specific examples of such structures and features described herein above and which for the sake of brevity and clarity have been omitted from the above description. Nonetheless, the above description should be read as implicitly including reference to such alternative structures and method features which provide equivalent functionality unless such alternative structures or method features are explicitly excluded in the above description of the examples of the present disclosure.
[0077] The examples of the present disclosure and the accompanying claims may be suitably combined in any manner apparent to one of ordinary skill in the art.
[0078] Whilst endeavouring in the foregoing specification to draw attention to those features of examples of the present disclosure believed to be of particular importance it should be understood that the applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.
1. An apparatus for exchanging heat comprising:
a first heat transfer member comprising a slot;
a second heat transfer member, physically separate from the first heat transfer member, wherein the second heat transfer member is movable with respect to the first heat transfer member, and wherein at least a part of the second heat transfer member is configured to pass through the slot, thereby defining a proximal portion of the second heat transfer member which is within the slot and;
a heat exchange region configured to transfer heat between the first heat transfer member and the second heat transfer member, the heat exchange region comprising the slot and the proximal portion.
2. The apparatus of claim 1, wherein apparatus is configured such that heat transfer
between the proximal portion and the slot occurs predominately via conduction.
3. The apparatus of any one or more of the previous claims, wherein the proximal portion
within the slot is separated from the slot by a separation distance of less than one
or more of: 1 mm, 0.1 mm, 50µ, 25µ, 10µ, 5µ
4. The apparatus of any one or more of the previous claims, wherein the thickness of
the at least part of the second heat transfer member is less than one or more of:
5mm, 1 mm, 0.1 mm, 50µ and 5µ.
5. The apparatus of any one or more of the previous claims, wherein an area the second
heat transfer medium outside of the slot is: 25%, 50%, 100%, 200% or 500% larger than
an area of second heat transfer medium within the slot.
6. The apparatus of any one or more of the previous claims, further comprising a plurality
of second heat transfer members.
7. The apparatus of any one or more of the previous claims, further comprising a plurality
of slots.
8. The apparatus of claim 6 or 7, wherein a separation distance between adjacent second
heat transfer members of the plurality of second heat transfer members varies along
the length of the adjacent second heat transfer members.
9. The apparatus of claim 6, 7 or 8, further comprising a second plurality of second
heat transfer members configured to interleave with the plurality of second heat transfer
members.
10. The apparatus of any one or more of the previous claims, further comprising means
for passing a fluid over an area the second heat transfer medium outside of the slot.
11. The apparatus of any one or more of the previous claims, wherein the second heat transfer
member is made of one or more of:
a non-metallic material, a polymer, and a flexible material.
12. The apparatus of any one or more of the previous claims, wherein the apparatus is
configured such that the second heat transfer member passes through the slot.
13. A module comprising the apparatus of any one or more of previous claims 1 to 12.
14. A heat exchanger, heat sink or device comprising the apparatus of any one or more
of previous claims 1 to 12, or the module of claim 13.
15. A method for exchanging heat between a first heat transfer member and at least a second
heat transfer member, the method comprising causing, at least in part, actions that
result in:
passing at least a part of the at least second heat transfer member through at least one slot of the first heat transfer member so as to enable the transfer heat therebetween.