US20050061473A1 - Flexible heat exchangers - Google Patents

Abstract

A heat exchanger for heating or cooling objects is flexible and can conform to surface profiles of objects to be warmed or cooled. The heat exchanger has a volume having at least one inlet for receiving a heat exchange fluid and at least one outlet. A flexible plate essentially impermeable to the heat exchange fluid is penetrated by substantially rigid thermally conductive members. The members provide paths of high thermal conductivity through the plate. The heat exchange fluid may be water based.

Description

TECHNICAL FIELD
• The invention relates to heat exchangers. The invention has broad application to heat exchangers used to deliver heat to or remove heat from objects as diverse as electrical or electronic devices or equipment, mechanical devices such as transmissions, spindles, compressors and engines, scientific and medical apparatus, living creatures, and the like.
BACKGROUND
• There are numerous situations where it is desirable to remove heat from an object or to deliver heat to an object. Various types of heat exchanger exist. Air cooled heat sinks are structures which take heat from an object and dissipate the heat into ambient air. Such heat sinks typically consist of a finned piece of thermally conductive material having a face which can be placed in thermal contact with an object, such as an electronic component, to be cooled. Some heat sinks are equipped with fans located to flow air past the fins to improve the rate at which heat is dissipated.
• U.S. Pat. No. 6,549,411 B1 discloses a flexible heat sink that can be attached to a generally flat surface of an object. The heat sink can flex to conform to the surface of the object to achieve improved contact with the object, and hence increase the efficiency of heat transfer between the heat sink and the object. U.S. Pat. No. 6,367,541 B2 discloses a heat sink that can be attached to multiple electronic chips which have different heights. The heat sink dissipates heat from the chips into ambient air.
• U.S. Pat. No. 5,368,093 discloses a flexible bag filled with thermal transfer fluid useful for thawing frozen foods. U.S. Pat. No. 4,910,978 discloses a flexible pack containing a gel. The pack can be cooled and applied to a patient for cold therapy. The pack conforms to surface contours of the patient's body. These devices have limited cooling capacities.
• More sophisticated heat exchangers use a heat exchange fluid, typically a liquid, instead of ambient air to carry heat away from or provide heat to an object to be cooled or heated. U.S. Pat. No. 5,757,615 discloses a flexible heat exchanger with circulating water as a coolant for cooling a notebook computer. U.S. Pat. No. 5,643,336 discloses a flexible heating or cooling pad with circulating fluid for therapeutically treating the orbital, frontal, nasal and peri-oral regions of a patient's head. U.S. Pat. No. 6,551,347 B1 discloses a flexible heat exchange structure having fluid-conducting channels formed between two layers of flexible material for heat/cold and pressure therapy. U.S. Pat. Nos. 6,197,045 B1 and 6,375,674 B1 disclose a flexible medical pad with an adhesive surface for adhering the pad to the skin of a patient. U.S. Pat. No. 6,030,412 discloses a flexible enveloping member for enveloping a head, neck, and upper back of a mammal for cooling the brain of the mammal suffering a brain injury. All of these heat exchangers require heat to pass through a layer of some flexible material such as rubber, or a flexible plastic such as polyurethane. In addition, heat is exchanged between the surface of the flexible material and a circulating fluid. Water is the most commonly used circulating fluid.
• Rubber and flexible plastics are poor conductors of heat. To provide a high heat transfer efficiency in a flexible heat exchanger in which heat is transferred across a layer of rubber or plastic the layer must be very thin. This makes such heat exchangers prone to damage. In addition, water is a poor heat conductor. Heat exchange between the flexible material and water is largely dependent on convection. Water flowing over a relatively flat surface will not result in efficient heat exchange.
• U.S. Pat. No. 3,825,063 discloses a heat exchanger having metal screens of fine mesh with internal plastic barriers that at least partly penetrate the screens. The screens are stacked to provide transverse heat conduction relative to longitudinal flow paths. U.S. Pat. No. 4,403,653 discloses a heat transfer panel comprising a woven wire mesh core embedded in a layer of plastic material. The mesh and closure layer extend in the same longitudinal direction. U.S. Pat. No. 5,660,917 discloses a sheet with electrically insulating thermal conductors embedded in it. The apparatus disclosed in those patents is not adapted for warming or cooling living subjects.
• There remains a need for heat exchangers capable of providing high heat transfer rates between the heat exchangers and objects that are not flat, are vibrating or are otherwise difficult to interface to. There is a particular need for such heat exchangers which have high ratio of heat-transfer capacity to contact area.
SUMMARY OF THE INVENTION
• The invention relates to heat exchangers. One aspect of the invention provides flexible heat exchange interfaces. The interfaces have plates of elastomeric material penetrated by substantially rigid thermally conductive members. The thermally conductive members have enlarged pads on at least one side of the plate.
• The elastomeric material allows the interfaces to flex while the thermally conductive members are operative to channel heat from a higher-temperature side of the interface to a lower-temperature side of the interface.
• Another aspect of the invention provides a flexible heat exchanger comprising a volume having an inlet and an outlet. The volume can receive a heat exchange fluid, for example, water or a water-based coolant. The heat exchanger includes a flexible plate. Substantially rigid thermally conductive members extend through a flexible material of the flexible plate from an outside surface of the flexible plate into the volume.
• In preferred embodiments the thermally conductive members each have a thermal conductivity of at least 50 Wm⁻¹K⁻¹and preferably at least 100 Wm⁻¹K⁻¹. The thermally conductive elements may be made of materials such as aluminum, copper, gold, silver, alloys of two or more of aluminum, copper, gold, or silver with one another, alloys of one or more of aluminum, copper, gold, or silver with one or more other metals, carbon, graphite, diamond, or sapphire.
• The thermally conductive members may cover a substantial portion of the outer surface of the flexible heat exchange plate. For example, the thermally conductive members may be exposed in an area of at least 50%, preferably at least 70% and, in some embodiments, at least 80% of an area of the flexible heat exchange plate.
• The flexible material of the plate may comprise an elastomer material. The thermally conductive members may be embedded in the elastomer material by any suitable process. The elastomer material may comprise, for example, natural rubber, polyurethane, polypropylene, polyethylene, ethylene-vinyl acetate, polyvinyl chloride, silicone, or a combination of two or more of polyurethane, polypropylene, polyethylene, ethylene-vinyl acetate, polyvinyl chloride, and silicone. In some embodiments the elastomer material has a thermal conductivity not exceeding 5 Wm⁻¹K⁻¹.
• A further aspect of the invention provides a temperature control system comprising a heat exchanger according to the invention, a reservoir containing a heat exchange fluid; a first feed pump connected to feed heat exchange fluid from the reservoir into the heat exchanger and a second feed pump connected to withdraw the heat exchange fluid from the reservoir.
• Further aspects of the invention and features of specific embodiments of the invention are described below.
BRIEF DESCRIPTION OF THE DRAWINGS
• In drawings which illustrate non-limiting embodiments of the invention:
• FIGS. 1A, 1B and1C are respectively a longitudinal elevational cross-section view; a top plan view and a bottom plan view of a flexible heat exchanger;
• FIGS. 2A, 2B and2C are respectively a cross-section view; a bottom view; and a top view of the flexible plate of a heat exchanger according to an alternative embodiment of the invention;
• FIG. 2D is a partial view of the outside surface of a heat exchanger having thermally conductive members arranged in a triangular array;
• FIG. 2E is a partial view of the outside surface of a heat exchanger having thermally conductive members arranged to provide converging lines of flexible material;
• FIG. 2F is a view of the outside surface of a heat exchanger having thermally conductive members arranged in a rectangular array oriented at an angle to a long axis of the heat exchanger;
• FIGS. 3A, 3B and3C are respectively a cross-section view; a bottom view; and a top view of a heat exchanger according to one embodiment of the invention;
• FIGS. 4A through 4L are views of different heat conductors that can be used in heat exchangers according to different embodiments of the invention;
• FIGS. 5A and 5B are respectively an isometric view and a longitudinal elevational section through a pre-curved flexible fluid heat exchanger;
• FIGS. 6A, 6B,6C and6D are schematic views of heat exchangers according to the invention being applied to cool various types of apparatus;
• FIG. 7 is a schematic view of a heat exchanger according to the invention being used to exchange heat with a very hot object;
• FIGS. 8A and 8B are cross-section views of heat exchange interfaces having pads on two sides; and,
• FIGS. 9, 10 and11 are schematic views of cooling systems according to the invention.
DESCRIPTION
• Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive, sense.
• Heat exchangers according to the invention have thermally conductive members which can be placed in thermal contact with an object to be heated or cooled. The thermally conductive members pass through a membrane of a flexible material. In some embodiments the membrane is essentially impermeable to a heat exchange fluid that contacts portions of the thermally conductive members that are distal to the object. The membrane permits the heat exchange members to move relative to one another to conform with surface contours of the object. For example, the membrane may permit the members to conform to a convex and/or concave curved surface on the object.
• The thermally conductive members accept heat from a higher-temperature side of the membrane, channel the heat through the membrane, and release the heat to a lower-temperature side of the membrane. The members provide much lower thermal resistance than would be the case if the members were not present.
• In some embodiments, the members have pads on their ends proximate to the object. The pads are dimensioned and distributed in such a manner that the pads cover a large proportion of a heat exchange area of the membrane. In certain embodiments of the invention, pads of a plurality of the thermally conductive members cover at least 50%, preferably at least 70%, and most preferably at least 80% of an area of the outer side of the membrane.
• An inner side of the membrane may define one side of a channel which carries a heat exchange fluid. Heat exchange fluid may be driven to flow through the channel by way of a suitable pumping system to deliver heat to, or draw heat from, the thermally conductive members.
• In some embodiments of the invention a plurality of the thermally conductive members have thermally conductive projections, which may comprise, for example, pins, fins, bars, plates or the like that project into the volume of a heat exchanger to form an efficient heat exchange interface with heat exchange fluid in the volume. The projecting pins, fins, bars, plates or the like may or may not be similar in shape or other physical characteristics to the parts of the thermally conductive members that extend through the membrane to form thermal channels through the membrane.
• The thermally conductive members may be made of any suitable thermally conductive materials including thermally conductive metals, for example, aluminum, copper, gold, silver, or alloys of these metals with one another and/or with other metals. The thermally conductive members may also be made of non-metals which have high thermal conductivities such as carbon, suitable grades of graphite, diamond, sapphire or the like. Preferably the thermally conductive members are made from materials having thermal conductivities, k, of at least 50 Wm⁻¹K⁻¹and preferably at least 100 Wm⁻¹K⁻¹.
• FIGS. 1A through 1C show aheat exchanger10 according to an embodiment of the invention.Heat exchanger10 has aheat exchange plate12 penetrated by a number of thermallyconductive members14.Plate12 has anouter face16 and aninner face18.Heat exchanger10 has aninside volume20 andports22,23 by way of which a heat exchange fluid can flow throughvolume20.Volume20 is defined on a front side byplate12 and on a rear side by arear wall24.Side walls25 extend betweenplate12 andrear wall24.Plate12,rear wall24 andside walls25 are all flexible so that theouter surface16 ofheat exchanger10 can conform to the local contours of a portion of an object to be heated or cooled.
• Thermallyconductive members14 pass through thematerial30 ofplate12. Inside ends26 of thermallyconductive members14 project intovolume20. Ends26 preferably project significantly intovolume20. In the embodiment shown inFIG. 1, ends26 are cut away to provide increased surface area for heat transfer with fluid involume20. Eachinner end26 comprises a number ofprongs27. Outer faces28 ofpads29 on the proximal ends of thermallyconductive members14 can be placed against an object.Pads29 are separated sufficiently to permitheat exchanger10 to flex in a desired degree but are preferably closely spaced to maximize the area ofouter faces28 that can be placed against a desired region on an object. For example, in some embodiments,pads29 are spaced apart from one another by spacings in the range of 0.5 mm to 50 mm. For smaller heat exchangers the spacing betweenpads29 is typically at the lower end of this range (i.e. in the range of 0 mm to 5 mm).
• In some embodiments,pads29 have thicknesses in the range of 0.5 mm to 5 mm. Preferably,pads29 have thicknesses in the range of 1 mm to 2.5 mm. The sizes and dimensions ofpads29 in the plane ofplate12 may be chosen to suit the application, taking into consideration the contours of the object to be cooled or heated.
• Thermallyconductive members14 may have reduced cross sectional areas in their portions towardinner face18 frompads29. The cross-sectional area of thermallyconductive members14 at the point that thermallyconductive members14 emerge frommaterial30 oninner face18 ofplate12 may, for example, be in the range of 20% to 100%, and in some embodiments is 35% to 65%, of the area ofpads29.
• Thermallyconductive members14 have lengths sufficient to pass throughmaterial30. In preferred embodiments,members14 project intovolume20. Thermallyconductive members14 may, for example, project intovolume20 for a distance in the range of 0 mm to 100 mm. For small heat exchangers the projection may be at the lower end of this range (i.e. in the range of 0 mm to 20 mm). The portions ofmembers14 which project intovolume20 may also function as supports to maintain a minimum spacing betweenwall24 andplate12. These portions may constitute spacing means for preventingrear wall24 from collapsing againstplate12.
• It is not necessary that all thermallyconductive members14 be identical or that all thermallyconductive members14 have equal-sized pads29 although it is convenient to makeheat exchanger10 with thermallyconductive members14 substantially the same as one another.
• Material30 constitutes a flexible membrane through which thermallyconductive members14 extend. In some embodiments,rear wall24 is made ofmaterial30. Substantially all ofheat exchanger10, except for thermallyconductive members14, may be made of thesame material30.Material30 is preferably both flexible and elastically stretchable.Material30 may, for example, comprise natural rubber or any of a variety of suitable flexible polymers such as polyurethane, polypropylene, polyethylene, ethylene-vinyl acetate, polyvinyl chloride, silicone, a combination of these materials or the like.Material30, or portions ofmaterial30 may optionally be loaded with particles of one or more thermally conductive materials such as metal or graphite. However, sincematerial30 is not required to play a significant role in conducting heat,material30 may be a material having a relatively low thermal conductivity (i.e. a thermal conductivity not exceeding 5 Wm⁻¹K⁻¹) without significantly impairing the function ofheat exchanger10. In some embodiments,material30 has a hardness in the range of 10 to 80 on the Shore A hardness scale.
• Plate12 may be fabricated using any suitable process. For example,plate12 may be made by making holes in a sheet ofmaterial30 and inserting thermallyconductive members14 through the holes. The holes may initially have dimensions smaller than corresponding dimensions of thermallyconductive members14 so that material30 seals around thermallyconductive members14 sufficiently to prevent any significant loss of heat exchange fluid fromvolume20. Additionally, or in the alternative, a sealant, such as a suitable glue, may be provided to enhance the seal between thermallyconductive members14 andmaterial30.Plate12 may also be made by a suitable plastic manufacturing process such as thermal injection molding, reaction injection molding, compression molding, vacuum forming or casting. In this case, thermallyconductive members14 may be molded intoplate12.
• The thickness ofmaterial30 inplate12 can be selected to provide a desired compromise between flexibility and durability. Sinceheat exchanger10 does not rely onmaterial30 to conduct heat, it is not necessary to makematerial30 extremely thin to improve heat conduction.Material30 may, for example, have a thickness in the range of about 1 mm to 20 mm. In some currently preferred embodiments of the invention,material30 has a thickness in the range of 3 mm to 7 mm inplate12.
• Projections ofmaterial30, or some other material, may optionally extend intovolume20. Such projections may be positioned to supportwall24 relative to plate12, to direct the flow offluid65 withinvolume20 and/or to induce turbulence at selected locations in the flow offluid65 in order to provide enhanced thermal contact between thermallyconductive members14 andheat exchange fluid65. Such projections may constitute spacing means for preventingrear wall24 from collapsing againstplate12.
• Thermallyconductive members14 may be arranged in a wide range of patterns. For example, as shown inFIG. 1,members14 may be arranged in rows and columns to form a rectangular array, which could be a square array. In some embodiments,members14 are arranged in rows or columns which are shifted relative to one another as shown inFIGS. 2B and 2C. This arrangement creates increased turbulence in fluid flowing throughvolume20 and hence increases the efficiency of heat transfer between the inner ends of thermallyconductive members14 andfluid65. In some embodiments, pads ofmembers14 are arranged in a rectangular array as illustrated, for example, inFIG. 1, while portions ofmembers14 which project intovolume20 are arranged in rows or columns which are shifted relative to one another as shown inFIGS. 2B and 2C. In some embodiments,members14 are arranged in a triangular array, as shown inFIG. 2D.
• Flexing ofplate12 may be facilitated by arrangingmembers14 to provide substantiallyunbroken lines31 ofmaterial30 extending generally parallel to one or more axes about whichheat exchanger10 may be flexed. The embodiment shown inFIG. 1B shows two sets oflines31 ofmaterial30 which extend between adjacent rows and columns ofmembers14. The embodiment illustrated inFIG. 2B has one set ofparallel lines31.Lines31 are not necessarily parallel to one another. For example,FIG. 2E illustrates an arrangement ofmembers14 which facilitates flexing in such a way as to conform to a portion of the surface of a cone. The array ofmembers14 is not necessarily aligned with any axis ofheat exchanger10. For example,FIG. 2F shows the outside face of a heat exchanger wherein thermallyconductive members14 are arranged in a rectangular array oriented at an angle, φ, to a long axis of the heat exchanger.
• FIGS. 2A to2F and3A to3C illustrate heat exchangers in which faces28 are substantially flush withmaterial30 onouter face16. This arrangement facilitates cleaning, asouter face16 is substantially smooth.FIGS. 1A to1C illustrate an embodiment of the invention whereinpads29 project frommaterial30 onouter surface16 ofheat exchanger10. The embodiment illustrated inFIGS. 1A to1C can be fabricated, for example, by inserting thermallyconductive members14 though holes formed in a sheet ofmaterial30.
• Thermallyconductive members14 may take any of a wide variety of forms which provide effective means to transfer heat from a higher-temperature side to a lower-temperature side of the membrane. The members preferably provide good thermal interface between the thermally conductive members and the object to be cooled or heated, good thermal channels acrossmembrane material30, and good thermal interface between the thermally conductive members and the heat exchange fluid involume20 of the thermal exchanger.
• Some possible forms formembers14 are illustrated inFIGS. 4A through 4K. It is understood that these possible forms are illustrated as examples and modifications to these examples can be made to obtain a much larger list of examples. In addition, features illustrated in these examples can be swapped or combined partially or fully to obtain an even larger list of examples.FIG. 4A shows a thermallyconductive member14A having asquare pad29 andcylindrical pin32 as means to channel heat throughmaterial30 and to release heat into (or take heat from) the fluid involume20 of the heat exchanger.FIG. 4B shows a thermallyconductive member14B having acircular pad29 instead of a square pad.
• FIG. 4C shows a thermallyconductive member14C wherein bothpad29 and thepin32 are square in cross-section (like the thermally conductive members ofFIGS. 2A to2C).FIG. 4D shows a thermallyconductive member14D similar tomember14A except thatpin32 has acircumferential groove33 in its part close topads29.Groove33 receivesextra material30 in an injection molding or casting process tobetter seal member14D tomaterial30.FIG. 4E shows a thermallyconductive member14E wherein a tip ofpin32 is tapered to facilitate insertion into a hole in a sheet ofmaterial30.
• FIG. 4F shows a thermallyconductive member14F having a pair of platelikerectangular conductors34.Conductors34 carry heat throughmaterial30 and provide a mechanism for releasing heat into (or taking heat from) heat exchange fluid involume20.Conductors34 may be arranged in a V-shape to better transfer heat to fluid flowingpast plates34. Plate-like conductors could also be arranged in other manners such as being parallel with each other. Thermallyconductive member14F has the advantage that it can be made by cutting and folding a thermally conductive sheet material.
• FIG. 4G shows a thermallyconductive element14G having a thermal channel portion provided by atubular pin36.FIG. 4H shows a thermallyconductive member14H havingmultiple pins38 extending frompads29.Pins38 provide multiple thermal channels extending from thesame pad29 and projecting intovolume30.Conductive member14H advantageously provides increased contact area betweenconductive member14H and a heat transfer fluid involume20.FIGS. 4I and 4J show a thermally conductive member14I that is designed to reduce the possibility of fluid leaking betweenmaterial30 and member14I. Member14I may be fabricated in two-pieces14I-1 and14I-2 that can be assembled together in a manner that provides good thermal contact between pieces14I-1 and14I-2. In the illustrated embodiment, one of the pieces of member14I has apin39 which is received in a corresponding socket40 (seeFIG. 4J) in the other piece.Pin39 may have an interference fit insocket40 to keep the two pieces tightly together and to provide good heat transfer between the pieces. Acircumferentially extending groove41 is defined between pieces14I-1 and14I-2.Groove41 receivesmaterial30. The faces of pieces14I-1 and14I-2 whichcontact material30 may be undercut to provideridges42 which help to prevent fluid from leaking past member14I. The pieces of multi-piece thermally conductive members may be fastened together in other ways which provide thermal contact between the pieces. For example, fastening means such as screws, rivets, or the like may be provided.FIGS. 4K and 4L show a thermallyconductive member14K that is similar to member14I but is an integral part.Member14K is designed to be cramped ontomaterial30.Material30 projects into agroove43. The sides of thegroove43 may be cramped together to holdmaterial30 around the edges ofmember14K as shown inFIG. 4L.
• FIGS. 5A and 5B show a flexible fluid heat exchanger50 which is normally curved in the absence of applied forces. Heat exchanger50 may be used to apply heat to or to cool a substantially cylindrical object. Apart from being curved, heat exchanger50 is similar toheat exchanger10 ofFIGS. 1A through 1C.
• Heat exchangers according to the invention may be pre-formed so thatsurface16 has a concave and/or convex curvature in the absence of applied forces.FIGS. 5A and 5B show a heat exchanger in which surface16 has a pre-formed concave curvature.
• Heat exchangers according to the invention may be applied to heating or cooling objects of diverse types. For example,FIG. 6A shows aheat exchanger10 being used to cool anelectric motor52.Pads29 contact the curvedouter surface53 ofmotor52.FIG. 6B shows aheat exchanger10 being applied to cool acompressor54 having anouter housing55 which has a profile having compound curvature.Pads29contact surface55. Compressors having compound curves are frequently used in refrigeration and air conditioning systems.FIGS. 6C and 6D show aheat exchanger10 being applied to cool anexchange pipe56.Pads29 contact an outercylindrical surface57 ofexhaust pipe56.
• FIG. 7 illustrates schematically aheat exchanger58 being used to cool anobject59 having a temperature high enough that it could cause degradation ofmaterial30.Heat exchanger58 is similar toheat exchanger10 except thatpads29 are spaced away frommaterial30,members14 are longer and aheat shield60 is provided betweenpads29 andmaterial30. Each of thermallyconductive members14 extends through a thermally insulatingsleeve59A.Sleeves59A protectmaterial30 from becoming overheated through contact withmembers14.Shield60 protectsmaterial30 from heat radiated byobject59.
• Heat exchangers according to the invention may also be used to transfer heat between fluids and/or between solid objects.FIG. 8A shows aheat exchanger61 comprising a membrane of a material30 penetrated by thermallyconductive members62.Members62 havepads29 on both sides ofmaterial30. As shown inFIG. 8B,pads29 can optionally comprise fins, pins or other thermally conductive elements disposed to provide improved thermal contact betweenpad29 and a surrounding fluid. Theheat exchanger61A illustrated inFIG. 8B haspins32 projecting from eachpad29.Pads29 are larger in area than the central portions ofmembers14 which pass throughmaterial30. The edges of the pads press against the membrane to seal any gap between the member and the membrane so that fluid will not leak from one side to the other.
• A suitable circulation system may be used to circulate a heat exchange fluid through thevolume20 of one or more heat exchangers as described herein. Water has a high specific heat capacity which makes water or water-based coolants good for use as a circulatingfluid65 in cases where fluid65 can operate at temperatures where such coolants are liquid.
• It is generally desirable to maintain the pressure of fluid involume20 approximately equal to the ambient air pressure surroundingheat exchanger10. If the pressure withinvolume20 is significantly smaller than the ambient air pressure then pressure differences across the walls ofvolume20 will tend to collapsevolume20. The projected ends26 of thermallyconductive members14 or other supports provided inheat exchanger10 may prevent the walls from complete collapse. If the pressure withinvolume20 is significantly larger than the ambient air pressure thenheat exchanger10 will tend to balloon.
• FIG. 9 is a schematic view of acooling system100 which includes aheat exchanger10 and afluid circulating system63.Circulation system63 has an insulatedreservoir64 containing a volume ofice66.System63 contains a suitableheat exchange fluid65, which may be liquid water.System63 deliversfluid65 toheat exchanger10 throughdelivery conduit67 and returns coolant toreservoir63 through areturn conduit68.
• Afirst feed pump70 upstream fromheat exchanger10 delivers fluid65 fromreservoir64 toheat exchanger10. Asecond feed pump72 is located downstream fromheat exchanger10.Second feed pump72 draws fluid65 fromheat exchanger10 and returns the fluid toreservoir64. First and second feed pumps70 and72 are balanced so that the pressure offluid65 withinvolume20 ofheat exchanger10 is substantially equal to the ambient air pressure.
• One or more bypass valves may be provided to provide better control over fluid pressure withinvolume20. Insystem100, anadjustable bypass valve74 is connected between the output offirst feed pump70 andreservoir64.Bypass valve74 indirectly regulates the pressure withinvolume20. Whenbypass valve74 is opened, a larger proportion offluid65 is returned toreservoir64 by way ofbypass conduit75 and the amount offluid65 flowing intoheat exchanger10 is reduced.Bypass valve74 may be pressure-operated.
• System100 has asecond bypass valve76 connected in parallel withsecond feed pump72. Whensecond bypass valve76 is open,second feed pump72 can draw fluid65 fromreservoir64 by way ofconduit77. Openingsecond bypass valve76 increases pressure at the input ofsecond feed pump72 and consequently increases the pressure withinvolume20.
• Many variations ofsystem100 are possible. Although two bypass valves are shown inFIG. 9 for maximum flexibility, one bypass valve connected in parallel with either one ofpumps70 or72 or in parallel withheat exchanger10 may be sufficient to permit pressure insideheat exchanger10 to be maintained within a desired range. In addition, depending upon the construction ofpumps70 and72 and the fluid flow properties of the circuit which includesconduits67,68 andheat exchanger10 it may be possible to maintain the fluid pressure involume20 within the desired range without the need forbypass valves74 and76. Where bypass valves are provided it is not necessary that they be connected directly toreservoir64 as illustrated. Other connections may be provided which have the result of maintaining pressures upstream and/or downstream fromheat exchanger10 at values which keep the pressure withinvolume20 at a desired level while maintaining fluid flow throughvolume20.
• In some cases it may be convenient to provide asingle reservoir64 for providing heat exchange fluid formultiple heat exchangers10. In such cases it is best to provide upstream anddownstream pumps70 and72 for eachheat exchanger10. In the alternative, suitable manifolds, such as T-connectors, could be provided to allow a number ofheat exchangers10 to be connected in parallel between a single upstream pump system and a single downstream pump system.
• FIG. 10 illustrates anotherfluid circulating system100A. Insystem100A, afirst flow regulator78 comprising a restrictor80 and abypass valve82 is provided betweenfirst feed pump70 andheat exchanger10.Bypass valve82 is connected in parallel withrestrictor80. When fluid65 is flowing throughflow regulator78 then a pressure drop acrossflow regulator78 depends upon the fluid flow rate and upon the degree to whichbypass valve82 is open.
• System61A has asecond flow regulator79 which includes asecond flow restrictor84 and abypass valve86.Bypass valve86 is connected in parallel withrestrictor84. Insystem100A,bypass valves82 and86 are adjustable. The fluid pressure withinvolume20 can be controlled by adjusting one or both ofbypass valves82 and86.
• Some alternative embodiments of the invention lack one offlow regulators78 and79. Whensystem100A is connected to supplyfluid65 to a plurality ofheat exchangers10 it is preferable to provide for eachheat exchanger10 at least oneadjustable flow regulator78 or79 located where only fluid going to or from that heat exchanger passes through the flow regulator. This permits the pressure within eachheat exchanger10 to be individually regulated. In the alternative, as described above, suitable manifolds may be provided to split the flow offluid65 between a number ofheat exchangers10 connected in parallel.
• FIG. 11 illustrates another fluid circulating system10B. Insystem100B the pressure withinvolume20 ofheat exchanger10 is controlled by adjusting the rate of operation of one or both of upstream and downstream feed pumps70 and72. In some embodiments of the invention a control system simultaneously increases the rate of operation offeed pump70 and decreases the rate of operation offeed pump72 or vice versa. The rate of operation ofpumps70 and72 may be controlled by adjusting the rate of rotation of motors which drive the pumps, by adjusting displacements of the pumps, or the like.
• In the illustrated embodiment, control is accomplished by operating a power splitter88 (illustrated schematically by a potentiometer).Power splitter88 can be operated to increase the speed of amotor driving pump70 and to decrease the speed of amotor driving pump72 or vice versa.
• Systems100,100A and100B may be automatically controlled using any suitable control system. For example, a controller may be provided to operate bypass valves and/or control pump speeds or displacements by way of suitable actuators (not shown) as necessary to control pressure withinvolume20 to stay within a desired range. Those skilled in the art are familiar with suitable controllers. The controller may, for example, comprise a suitably programmed programmable controller or a hardware control circuit. One or more pressure sensors and/or flow sensors (not shown) may be included to provide feedback to the controller.
• Any of coolingsystems100,100A or100B may be adapted for warming by replacingice66 with a suitable heating element which can be operated towarm fluid65 inreservoir64 to a desired temperature. Instead ofice66, any ofsystems100,100A or100B could include a refrigeration system to coolfluid65.
• Where a component (e.g. a member, assembly, element, device, circuit, etc.) is referred to above, unless otherwise indicated, reference to that component (including a reference to a “means”) should be interpreted as including as equivalents of that component any component which performs the function of the described component (i.e., that is functionally equivalent), including components which are not structurally equivalent to the disclosed structure which performs the function in the illustrated exemplary embodiments of the invention.
• As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. For example:
• • Thermallyconductive members14 may have any suitable shapes and arrangements. Those illustrated herein are but examples.
  • Flexible material30 may have different compositions in different parts of a heat exchanger according to the invention. Different suitableflexible materials30 may be used formaterial30 in different parts of a heat exchanger.
  • A heat exchanger according to the invention is not necessarily rectangular or parallel-sided. A heat exchanger according to the invention could have other shapes. Heat exchangers according to some currently preferred embodiments of the invention are elongated and have fluid inlets and fluid outlets located in areas at opposed ends of a long axis.
    Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.

Claims (38)

1. A flexible heat exchange interface for use in a heat exchanger, the flexible interface comprising a plate of an elastomer material penetrated by a plurality of substantially rigid thermally conductive members, each of the plurality of thermally conductive members having a first enlarged pad on at least a first side of the plate.

2. A flexible heat exchange interface according toclaim 1 wherein each of the plurality of thermally conductive members project from a second side of the plate opposed to the first side of the plate.

3. A flexible heat exchange interface according toclaim 1 wherein each of the plurality of thermally conductive members has a second enlarged pad on a second side of the plate opposed to the first side of the plate.

4. A flexible heat exchange interface according toclaim 3 wherein at least one of the first and second enlarged pads is cramped around its edge against the elastomer material.

5. A flexible heat exchange interface according toclaim 3 wherein each of the plurality of thermally conductive members comprises first and second parts, the first part including the first pad and comprising a pin engaging a socket on the second part, the second part including the second pad.

6. A flexible heat exchange interface according toclaim 3 wherein at least one of the first and second enlarged pads comprises a plurality of projections, the projections projecting away from the plate.

7. A flexible heat exchanger comprising:

a volume having at least one inlet for receiving a heat exchange fluid and at least one outlet; and,

a flexible plate essentially impermeable to the heat exchange fluid, the plate comprising a plurality of substantially rigid thermally conductive members extending through a flexible material of the plate from an outside surface of the plate into the volume.

8. A flexible heat exchanger according toclaim 7 wherein the volume is defined between the plate and a flexible back wall spaced apart from the plate.

9. A flexible heat exchanger according toclaim 7 wherein the thermally conductive members are arranged in a rectangular array.

10 A flexible heat exchanger according toclaim 9 wherein the thermally conductive members each comprise a generally rectangular pads on the outside surface of the plate.

11. A flexible heat exchanger according toclaim 7 wherein the thermally conductive members are arranged in a triangular array.

12. A flexible heat exchanger according toclaim 7 wherein the thermally conductive members are arranged to provide a plurality of substantially unbroken lines of the flexible material extending between the thermally conductive members.

13. A flexible heat exchanger according toclaim 7 wherein the thermally conductive members each have a thermal conductivity of at least 50 Wm⁻¹K⁻¹.

14. A flexible heat exchanger according toclaim 7 wherein the thermally conductive members each have a thermal conductivity of at least 100 Wm⁻¹K⁻¹.

15. A flexible heat exchanger according toclaim 14 wherein the thermally conductive members are made of a material selected from the group consisting of: aluminum, copper, gold, silver, alloys of two or more of aluminum, copper, gold, or silver with one another and alloys of one or more of aluminum, copper, gold, or silver with one or more other metals.

16. A flexible heat exchanger according toclaim 13 wherein the thermally conductive members are made of materials selected from the group consisting of: carbon, graphite, diamond, and sapphire.

17. A flexible heat exchanger according toclaim 7 wherein a plurality of the thermally conductive members covers at least 70% of an area of the outer side of the heat exchange plate.

18. A flexible heat exchanger according toclaim 7 wherein the flexible material of the plate comprises an elastomer material and the thermally conductive members are embedded in the elastomer material.

19. A flexible heat exchanger according toclaim 18 wherein the elastomer material comprises a material selected from the group consisting of: polyurethane, polypropylene, polyethylene, ethylene-vinyl acetate, polyvinyl chloride, silicone, natural rubber and a combination of two or more of polyurethane, polypropylene, polyethylene, ethylene-vinyl acetate, polyvinyl chloride, and silicone.

20. A flexible heat exchanger according toclaim 7 wherein the thermally conductive members project into the volume.

21. A flexible heat exchanger according toclaim 20 wherein the thermally conductive members project into the volume from the inner surface of the plate by distances of at least 3 mm.

22. A flexible heat exchanger according toclaim 7 wherein the flexible material of the plate has a thermal conductivity not exceeding 5 Wm⁻¹K⁻¹.

23. A flexible heat exchanger according toclaim 7 wherein a plurality of the thermally conductive members each comprise an outer end comprising a pad on the outer side of the plate and an inner end projecting into the volume.

24. A flexible heat exchanger according toclaim 23 wherein the inner end of each of the plurality of thermally conductive members comprises a plurality of spaced apart projections.

25. A flexible heat exchanger according toclaim 23 wherein a plurality of the thermally conductive members each comprise a first part connected to the second part wherein the first and second parts define a circumferentially extending groove and the flexible material of the plate is received in the groove.

26. A flexible heat exchanger according toclaim 23 wherein the inner end of each of the thermally conductive members is tubular, square, rectangular, cylindrical or spherical.

27. A flexible heat exchanger according toclaim 7 wherein the outer surface has a concave curved configuration in the absence of bending forces acting on the heat exchanger.

28. A flexible heat exchanger according toclaim 7 wherein the outer surface has a convex curved configuration in the absence of bending forces acting on the heat exchanger.

29. A flexible heat exchanger according toclaim 7 wherein a portion of the outer surface of the heat exchanger on which the thermally conductive members are disposed is dimensioned to be applied exclusively to an area of a subject's anatomy overlying a carotid artery of the subject.

30. A flexible heat exchanger according toclaim 7 wherein a total area of the thermally conductive members exposed on the outside surface of the plate exceeds a total cross sectional area of the thermally conductive members at a point where the cross sectional members enter the volume.

31. A flexible heat exchanger according toclaim 7 wherein the volume is defined between a flexible rear wall and the flexible plate and the heat exchanger comprises spacing means for preventing the rear wall from collapsing against the flexible plate.

32. A flexible heat exchanger according toclaim 7 wherein the volume is defined between the flexible plate, a flexible rear wall made of the flexible material and flexible side walls made of the flexible material.

33. A temperature control system comprising:

a heat exchanger according toclaim 7;

a reservoir containing a heat exchange fluid;

a first feed pump connected to feed the heat exchange fluid from the reservoir into the input of the heat exchanger;

a second feed pump connected to withdraw the heat exchange fluid from the output of the heat exchanger.

34. A system according toclaim 33 comprising a controller connected to control operation of the first and second feed pumps to maintain a pressure of the heat exchange fluid within the volume within a desired range of an ambient air pressure outside the volume.

35. A system according toclaim 34 comprising an adjustable bypass valve connected in parallel with one of the first and second feed pumps wherein the controller is configured to operate an actuator to adjust the bypass valve.

36. A system according toclaim 33 comprising an adjustable bypass valve connected in parallel with one of the first and second feed pumps.

37. A system according toclaim 36 wherein the adjustable bypass valve is configured to be opened by a pressure differential across the bypass valve.

38. A system according toclaim 33 comprising a variable restriction connected between the heat exchanger and one of the feed pumps.

Images