Flexible Heat/Mass Exchanger
A flexible heat/mass exchanger constructed of flexible layers defining a flow channel and exterior surfaces. The heat/mass exchanger utilizes a working liquid, such as water, that is present in the flow channel during use. The heat/mass exchanger uses one or more porous and/or permeable materials to allow mass exchange between the working liquid in the flow channel and the environment surrounding the heat/mass exchanger. In a cooling mode, evaporation of the working liquid occurs via the mass exchange. In a dehumidification mode, moisture in the surrounding environment is transported to the working liquid via the mass exchange. In some embodiments, the heat/mass exchanger is made of a number of flexible sheets of material. One or more flexible heat/mass exchangers may be used to form a semi-closed system, such as a personal cooling system with a circulating coolant loop, or an open system, such as a personal hydration system.
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This application claims the benefit of priority of U.S. Provisional Patent Application Ser. No. 60/915,558, filed May 2, 2007, and titled “Flexible Laminated Heat/Mass Exchangers,” which is incorporated by reference herein in its entirety.
STATEMENT OF GOVERNMENT INTERESTSubject matter of this disclosure was made with government support under U.S. Army Contract No. W911QY-05-C-0008. The government may have certain rights in this subject matter.
FIELD OF THE INVENTIONThe present invention generally relates to the field of heat exchangers and liquid cooling. In particular, the present invention is directed to a flexible heat/mass exchanger.
BACKGROUNDThere is a growing interest in small-scale power, refrigeration, and thermal management systems that require small and efficient liquid/air heat exchangers for heat rejection. Often these systems are meant to be integrated with human-portable equipment, such as chemical/biological protective suits, personal hydration systems, and soldier-portable power systems. The environments where these applications are needed are often remote and difficult to access. Heat must be rejected to an easily available heat sink, which almost always is ambient air. Typically the liquid will flow through an array of passages with large exposed surface area. Ambient air will flow past the outer surfaces of the flow passages and absorb heat from the liquid.
Typical heat transfer assemblies are formed from metal or ceramic components, and can be heavy and rigid. Furthermore, most heat rejection components are designed to transfer heat across a solid boundary. Systems like this have limited cooling potential because the circulating fluid cannot be cooled to a temperature that is lower than the temperature of the surrounding air. In hot environments, effective cooling using a typical heat exchanger can be impossible.
SUMMARY OF THE DISCLOSUREIn one implementation, the present disclosure is directed to a system for use with a working liquid. The system comprises a heat/mass exchanger that includes: a thin flexible body having a first face and a second face spaced from the first face, the thin flexible body comprising a plurality of layers defining a flow field region containing at least one passageway and having boundary margins, the plurality of layers fluidly sealingly attached to one another at least at the boundary margins, wherein at least one of the plurality of layers is permeable so as to allow mass transfer of a portion of the working liquid from the at least one passageway to the first face of the thin flexible laminate when the heat/mass exchanger is in use.
In another implementation, the present disclosure is directed to a heat/mass exchanger for use with a working fluid in an ambient environment. The heat/mass exchanger includes: a flexible laminate having a flexible first sheet and a flexible second sheet fluidly sealed around a boundary region, each of the flexible first and second sheets having an external face exposed to the ambient environment during use; a flow channel defined by the flexible first sheet, the flexible second sheet and the boundary region, the flow channel containing the working fluid during use; and either or both the flexible first and second sheets configured to transport a portion of the working fluid from the flow channel to the external face of either or both of the flexible first and second sheets.
In yet another implementation, the present disclosure is directed to a hydration system that includes: a hydration reservoir for storing potable water during use; and a heat/mass exchanger fluidly coupled with the hydration reservoir downstream thereof, the heat/mass exchanger including: a thin flexible body having a first face and a second face spaced from the first face, the thin flexible body comprising a plurality of layers defining a flow channel region containing a flow channel and having boundary margins, the plurality of layers fluidly sealingly attached to one another at the boundary margins so as to define the flow channel; a water inlet fluidly coupled between the hydration reservoir and the flow channel for providing the potable water thereto; and a water outlet fluidly coupled to the flow channel for conducting the potable water therefrom; wherein at least one of the plurality of layers is permeable so as to allow mass transfer of a portion of the working liquid from the flow channel to the first face of the thin flexible laminate when the heat/mass exchanger is in use.
For the purpose of illustrating the invention, the drawings show aspects of one or more embodiments of the invention. However, it should be understood that the present invention is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein:
Referring now to the drawings,
In this connection, flexible heat/mass exchangers made in accordance with concepts of the present disclosure, such as flexible heat/mass exchanger 100, are characterizable as “thin” structures, i.e., structures having widths and lengths much greater than their thicknesses. Minimum width:thickness and length/thickness ratios are each about 100:1 and 300:1. Examples of structures meeting this criterion are sometimes characterized as sheets and ribbons, among others. Exemplary configurations of such highly efficient configurations for flow channel 112 are presented below in connection with
Heat/mass exchanger 100 may be conveniently described as comprising three layers, i.e., first and second outer layers 124, 128 and an intermediate layer 132 that contains flow channel 112. It is to be understood that while each of these layers 124, 128, 132 is shown in
First and second outer layers 124 and 128 may themselves comprise multiple layers of various materials. For example, some of the layers that make up the outer layers can serve as structural support, some may provide permeability to the exchanger's working fluid, and some may be present to simplify fabrication (for example by enabling bonding to the intermediate layer 132). Typically commercial “membrane” materials are assembled from multiple layers, each of which performs a separate function.
Exemplary materials of construction for layers 124, 128, and 132 include thin flexible polymeric sheets. Thin polymeric sheets provide enhanced heat and mass transfer as well as flexibility. The sheets may be formed in non-planer shapes for specific applications where form-fitting heat/mass transfer area is desirable. The sheets may be permeable or impermeable to the working liquid, or combinations thereof, though at least one sheet should exhibit at least partial permeability to facilitate mass transfer to or from an outer face, such as first outer face 104 or second outer face 108, of an external layer 124 or 128 respectively, of the heat/mass exchanger 100. For example, a permeable sheet may be composed of a material that is inherently impermeable but contain sufficient porosity to permit mass transfer, such as ePTFE (expanded polytetrafluoroethylene). Alternatively, a sheet may be formed from a solid hydrophilic membrane, such as urethane. Fluid may dissolve into the sheet and diffuse through the sheet material without passing through openings or other porous structures.
Intermediate layer 132 need not facilitate mass transfer through its solid components to an external face and so, if provided as one or more separate and distinct layers, may be manufactured from inherently permeable or inherently impermeable materials so as to promote flow of working fluid along the direction of arrows 136. In some embodiments, flow channel 112 includes interconnecting flow passageways that form a flow matrix (not explicitly shown in
It is noted that some of the materials used to make heat/mass exchangers of the present disclosure and the configurations of such heat/mass exchangers allow the heat/mass exchangers to be readily made/formed into a variety of shapes. For example, in some embodiments, the various layers 124, 128, 132 may be made of corresponding respective sheets of material that may be cut to any shape and suitably secured to one another while engaged with a shaping form, such as a convex of concave form, or engaged in a shaping mold, such as a mold having two parts that together define a cavity that contains the heat/mass exchanger during molding. As an illustrative example, a heat/mass exchanger of the present disclosure, such as heat/mass exchanger 100 of
When: 1) a liquid working fluid (represented in
The primary driving force for this process is the difference in chemical potential of the working fluid 136 between the flow channels 112 and surrounding air 144, not the difference in temperature. Therefore this cooling process can proceed even if the temperature of the surrounding air is greater than the temperature of the working fluid. The remaining portion of working fluid 136 transiting through flow channel 112 passes through the outlet manifold 120 and exits the heat/mass exchanger through an outlet fluid port 142. The additional cooling achieved through the evaporation mechanism provided by permeable first outer layer 124 is highlighted by
Referring now to
Referring to
The embodiment shown in
In addition, while channel 112 of exemplary heat/mass exchanger 100 of
Referring now to
In this example, heat/mass exchanger 300 includes integrated inlet/outlet manifolds 328, 332 formed in corresponding respective ones of first and second intermediate sheets 312, 316. This example also includes a pair of inlet/outlet ports 336, 340 in fluid communication with corresponding respective ones of integrated inlet/outlet manifolds 328, 332 for carrying a working liquid (not shown) to and from the respective inlet/outlet manifolds. Inlet/outlet ports 336, 340 are roughly positioned in the diagonal corners of the two overlain intermediate sheets 312, 316 in small tab-like extensions 344, 348 of the otherwise rectangular sheets, but still located over their respective inlet/outlet manifolds 328, 332. As those skilled in the art will readily appreciate, manifolds 328, 332 and ports 336, 340 are conveniently characterized as “inlet/outlet” simply because whether each manifold and port is an inlet-type or outlet-type depends only on the direction the working liquid flows through heat/mass exchanger 300. This convention is also used relative to heat/mass exchanger 400 of
In the example shown in
In this example, both first and second outer sheets 304, 308 are constructed from materials that permit working fluid mass, in either liquid or vapor form, to migrate to the respective first and second outer faces 352, 356 from the flow matrix, such as ePTFE or urethane. The construction of the various layers (i.e., layers 124, 128, 132 of diagrammatic heat/mass exchanger 100 of
In contrast to heat/mass exchanger 300 of
Referring now to
Referring again to
The volume of the flow channel in flow field region 524 may be any suitable size. For example, if compactness of heat/mass exchanger 400 is important, this volume may be limited to a single drink or sip by the user. In this example, cooling of the water in heat/mass exchanger 400 occurs primarily between drinks by the user while the water is stagnant. This single-drink volume of heat/mass exchanger 400 is best suited for occasional hydration since each time the user takes a drink, the entire volume of the heat/mass exchanger is refilled with warm uncooled water from hydration pack 500. In other embodiments, the liquid volume of the flow channel may be greater than the volume of one drink. This way, a greater volume of cooled water is available to the user at one time.
As seen in
Referring now to
The views of
First and second sheets 704, 708 may be made of any suitable material, such as any one or more of the non-permeable and permeable materials mentioned above relative to heat/mass exchangers 100, 300 of FIGS. 1 and 3A-C, respectively. One, the other, or both, of first and second sheets 704, 708 will be permeable so as to make flow matrix structure 700 provide the mass exchange functionality described above relative to, for example, heat/mass exchanger 100. The spacing, size, and height of depressions 712 may be determined as a function of one or more of a number of variables, such as the pressure of the liquid that will flow within flow channels 716, the amount of ballooning tolerable between depressions, and the physical properties of first and second sheets 704, 708, among others. First and second sheets 704, 708 may be fastened at depressions 712 using any fastening technique suitable for the materials chosen for the sheets, such as any one or more of the fastening techniques mentioned above relative to heat/mass exchanger 300 of
Sheets 804, 808 may be made of any suitable material(s) for the design contemplated and may be secured to one another by any suitable technique compatible with the materials used. The sizing and spacing of holes 820 and locations of connections between sheets 804, 808 may be determined as a function of a number of variables, such as the pressure of the liquid that will flow within flow channels 824, the amount of ballooning tolerable in the outer layers at the depressions, and the physical properties of the outer layers, among others. The basic structure of flow matrix structure 800 lends itself to many variations. For example, the shapes of holes 820 may be other than circular, such as oval, rectangular, and octagonal, one or both of single sheets 804, 808 may be replaced with multiple sheets. Similarly, the holes may be replaced by depressions that do not extend all the way through the respective sheets. In this last case, the resulting flow matrix structure could be executed in as few as two sheets, since the material of each sheet remaining at each depression would function as one or the other of first and second outer layers 124, 128 of heat/mass exchanger 100 of
Under the harsh and mobile conditions envisioned for many of the applications of a heat/mass exchanger made in accordance with the present disclosure, such heat/mass exchanger may be a component of a modularized unit which can be easily installed or replaced in the application it services. For example and referring to
As best seen in
Referring to
The variety of useable materials of construction and variety of methods of bonding these materials together create many possible embodiments of a heat/mass exchanger assembly made in accordance with the present disclosure that may have various configurations to meet different design and/or geometric requirements. In this connection,
In one embodiment, the heat/mass exchangers are fluidly connected in a parallel flow configuration. In this embodiment, an inlet port 1332 provides a working liquid, for example, water, to all heat/mass exchangers 1308 via an inlet header, which in this embodiment is formed by the inlets of the individual heat/mass exchangers. An outlet header, which in this embodiment is formed by the outlets of the individual heat/mass exchangers 1308, collects the working liquid from the heat/mass exchangers that has flowed through heat/mass exchanger assembly 1300 as indicated by arrows 1336 and communicates it to an outlet port 1340. In another embodiment, the heat/mass exchangers 1308 are fluidly connected in a series flow configuration. In this case, outlet port 1340 would connect with bottom-most heat/mass exchanger, on the side of stack 1304 that is opposite from inlet port 1332 (and not visible in
As will be understood by those skilled in the art, in a complete semi-closed system inlet and outlet ports 1332, 1340 would be connected, for example, to a liquid circulating loop that is coupled to a heat source desired to be cooled. An example of a semi-closed system is the personal cooling system 1000 of
Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions may be made to that which is specifically disclosed herein without departing from the spirit and scope of the present invention.
Claims
1. A system for use with a working liquid, comprising:
- a heat/mass exchanger that includes: a thin flexible body having a first face and a second face spaced from said first face, said thin flexible body comprising a plurality of layers defining a flow field region containing at least one passageway and having boundary margins, said plurality of layers fluidly sealingly attached to one another at least at said boundary margins; wherein at least one of said plurality of layers is permeable so as to allow mass transfer of a portion of the working liquid from said at least one passageway to said first face of said thin flexible laminate when said heat/mass exchanger is in use.
2. A system according to claim 1, wherein said flow field region contains a plurality of interconnecting flow channels, said plurality of layers fluidly sealingly attached to one another at multiple regions throughout said flow field region so as to define said plurality of interconnecting flow channels.
3. A system according to claim 2, wherein said thin flexible body comprises two polymeric outer sheets at least one polymeric intermediate sheet fluidly sealingly secured to said two outer polymeric sheets therebetween, said at least one polymeric intermediate sheet having a plurality of openings partially defining ones of said plurality of interconnecting channels.
4. A system according to claim 3, wherein said thin flexible body comprises two polymeric intermediate sheets sealingly secured to one another and having like openings formed therein, said like openings of one of said two polymeric intermediate sheets partially overlapping said like openings of the other of said two polymeric intermediate sheets, said like openings forming said plurality of interconnecting flow channels.
5. A system according to claim 4, wherein said two polymeric intermediate sheets include corresponding respective sets of elongate strips defining ones of said like openings, said two polymeric intermediate sheets oriented so that said elongate strips of said corresponding respective sets cross one another to form overlap regions, said elongate strips fastened to one another at said overlap regions.
6. A system according to claim 4, wherein said like openings form two-dimensional arrays on corresponding respective ones of said two polymeric intermediate sheets.
7. A system according to claim 6, wherein said like openings are circular.
8. A system according to claim 4, further comprising an inlet manifold and an outlet manifold in fluid communication with opposing ends of said plurality of interconnecting flow channels, said inlet and outlet manifolds formed by said two polymeric intermediate sheets.
9. A system according to claim 1, wherein said thin flexible body comprises two flexible sheets providing said first and second outer faces and defining said at least one passageway.
10. A system according to claim 9, wherein said at least one passageway is defined by partially overlapping sets of depressions formed in corresponding respective ones of said two flexible sheets.
11. A system according to claim 1, wherein the system is a personal hydration system comprising a human-wearable hydration pack, said mass/heat exchanger secured to said human-wearable hydration pack and in fluid communication therewith.
12. A system according to claim 1, wherein the system is a personal cooling system comprising a liquid cooled garment, said mass/heat exchanger in fluid communication with said liquid cooled garment so as to provide a circulation path for the working fluid to and from said liquid cooled garment.
13. A system according to claim 12, further comprising a makeup liquid reservoir in fluid communication with said heat/mass exchanger for making up a portion of the working liquid lost to the mass transfer.
14. A system according to claim 13, further comprising a fan, said fan and said heat/mass exchanger located so that said fan moves air across at least one of said first and second surfaces during use so as to assist evaporation of a portion of the working liquid therefrom.
15. A system according to claim 1, wherein said heat/mass exchanger comprises an inlet manifold, an outlet manifold and multiple ones of said thin flexible body, each of said multiple ones of said thin flexible body fluidly having a fluid inlet connected to said inlet manifold and a fluid outlet connected to said outlet manifold.
16. A system according to claim 1, wherein said thin flexible body comprises a sheet folded into a plurality of pleats.
17. A system according to claim 1, wherein said heat/mass exchanger has a central stacking axis and comprises multiple ones of said thin flexible body lying in corresponding respective planes perpendicular to said stacking axis, said multiple ones of said thin flexible body spaced from one another along said central stacking axis and defining a central open region surrounding said central stacking axis so that said central open region fluidly communicates with spaces between adjacent ones of said multiple ones of said thin flexible body.
18. A system according to claim 17, wherein said multiple ones of said thin flexible body are configured so that, during operation, the working fluid flows through said multiple ones of said thin flexible body circumferentially relative to said central stacking axis.
19. A system according to claim 18, further comprising a fan, said fan and said heat/mass exchanger configured so that air flows radially within said spaces between adjacent ones of said multiple ones of said thin flexible body.
20. A system according to claim 1, wherein said at least one of said plurality of layers that is permeable is permeable by virtue of a porous material.
21. A system according to claim 1, wherein said at least one of said plurality of layers that is permeable is permeable by virtue of a liquid impermeable, vapor permeable material.
22. A system according to claim 1, wherein said at least one passageway is provided by a three-dimensional fibrous sheet.
23. A heat/mass exchanger for use with a working fluid in an ambient environment, comprising:
- a flexible laminate having a flexible first sheet and a flexible second sheet fluidly sealed around a boundary region, each of said flexible first and second sheets having an external face exposed to the ambient environment during use;
- a flow channel defined by said flexible first sheet, said flexible second sheet and said boundary region, said flow channel containing the working fluid during use; and
- either or both said flexible first and second sheets configured to transport a portion of the working fluid from the flow channel to said external face of either or both of said flexible first and second sheets.
24. A heat/mass exchanger according to claim 23, wherein said flow channel is provided by a flow matrix of interconnecting flow passageways defined by said flexible first sheet, said flexible second sheet and said boundary region.
25. A heat/mass exchanger according to claim 24, wherein said flexible laminate comprises two flexible intermediate layers sealingly secured to one another and to said flexible first and second sheets and having like openings formed therein, said like openings of one of said two flexible intermediate layers partially overlapping said like openings of the other of said two flexible intermediate layers, said like openings forming said interconnecting flow passageways.
26. A heat/mass exchanger according to claim 25, wherein said two flexible intermediate layers include corresponding respective sets of elongate strips defining ones of said like openings, said two flexible intermediate layers oriented so that said elongate strips of said corresponding respective sets cross one another to form overlap regions, said elongate strips fastened to one another at said overlap regions.
27. A heat/mass exchanger according to claim 26, wherein said like openings form two-dimensional arrays on corresponding respective ones of said two flexible intermediate layers.
28. A heat/mass exchanger according to claim 27, wherein said like openings are circular.
29. A heat/mass exchanger according to claim 26, further comprising an inlet manifold and an outlet manifold in fluid communication with opposing ends of said interconnecting flow passageways, said inlet and outlet manifolds formed by said two flexible intermediate layers.
30. A heat/mass exchanger according to claim 24, wherein said interconnecting flow passageways are defined by partially overlapping sets of depressions formed in corresponding respective ones of said flexible first and second sheets.
31. A heat/mass exchanger according to claim 23, wherein said either or both said flexible first and second sheets is permeable by virtue of a porous material.
32. A heat/mass exchanger according to claim 23, wherein said either or both said flexible first and second sheets is permeable by virtue of a liquid impermeable, vapor permeable material.
33. A heat/mass exchanger according to claim 23, wherein said flow channel is provided by a three-dimensional fibrous sheet.
34. A hydration system, comprising:
- a hydration reservoir for storing potable water during use; and
- a heat/mass exchanger fluidly coupled with said hydration reservoir downstream thereof, said heat/mass exchanger including: a thin flexible body having a first face and a second face spaced from said first face, said thin flexible body comprising a plurality of layers defining a flow channel region containing a flow channel and having boundary margins, said plurality of layers fluidly sealingly attached to one another at said boundary margins so as to define said flow channel; a water inlet fluidly coupled between said hydration reservoir and said flow channel for providing the potable water thereto; and a water outlet fluidly coupled to said flow channel for conducting the potable water therefrom; wherein at least one of said plurality of layers is permeable so as to allow mass transfer of a portion of the working liquid from said flow channel to said first face of said thin flexible laminate when said heat/mass exchanger is in use.
35. A hydration system according to claim 34, wherein said hydration reservoir is contained in a human-portable hydration pack.
36. A hydration system according to claim 35, wherein said human-portable hydration pack has an exterior and said heat/mass exchanger is secured to said human-portable hydration pack on said exterior.
37. A hydration system according to claim 34, wherein said flow channel comprises a plurality of interconnecting flow passageways, said plurality of layers fluidly sealingly attached to one another at said boundary margins and attached to one another throughout said flow channel region so as to define said plurality of interconnecting flow passageways.
38. A hydration system according to claim 37, wherein said thin flexible body comprises two polymeric outer sheets at least one polymeric intermediate sheet fluidly sealingly secured to said two outer polymeric sheets therebetween, said at least one polymeric intermediate sheet having a plurality of openings partially defining ones of said plurality of interconnecting flow passageways.
39. A hydration system according to claim 37, wherein said thin flexible body comprises two polymeric intermediate sheets sealingly secured to one another and having like openings formed therein, said like openings of one of said two polymeric intermediate sheets partially overlapping said like openings of the other of said two polymeric intermediate sheets, said like openings forming said plurality of interconnecting flow passageways.
40. A hydration system according to claim 39, wherein said two polymeric intermediate sheets include corresponding respective sets of elongate strips defining ones of said like openings, said two polymeric intermediate sheets oriented so that said elongate strips of said corresponding respective sets cross one another to form overlap regions, said elongate strips fastened to one another at said overlap regions.
41. A hydration system according to claim 39, wherein said like openings form two-dimensional arrays on corresponding respective ones of said two polymeric intermediate sheets.
42. A hydration system according to claim 41, wherein said like openings are circular.
43. A hydration system according to claim 39, further comprising an inlet manifold and an outlet manifold in fluid communication with opposing ends of said interconnecting flow channels, said inlet and outlet manifolds formed by said two polymeric intermediate sheets.
44. A hydration system according to claim 37, wherein said thin flexible body comprises two flexible sheets providing said first and second outer faces and defining said interconnecting flow passageways.
45. A hydration system according to claim 44, wherein said interconnecting flow channels are defined by partially overlapping sets of depressions formed in corresponding respective ones of said two flexible sheets.
46. A hydration system according to claim 34, wherein said at least one of said plurality of layers that is permeable is permeable by virtue of a porous material.
47. A hydration system according to claim 34, wherein said at least one of said plurality of layers that is permeable is permeable by virtue of a liquid impermeable, vapor permeable material.
48. A hydration system according to claim 34, wherein air is forced across the permeable face of the heat/mass exchanger by an air-moving device.
49. A hydration system according to claim 34, wherein said flow channel is provided by a three-dimensional fibrous sheet.
Type: Application
Filed: May 2, 2008
Publication Date: Jun 3, 2010
Applicant: CREARE, INC. (Hanover, NH)
Inventors: Michael G. Izenson (Hanover, NH), Weibo Chen (Hanover, NH)
Application Number: 12/598,114
International Classification: F28F 3/12 (20060101); F28F 9/02 (20060101);