U.S. patent application number 12/598114 was filed with the patent office on 2010-06-03 for flexible heat/mass exchanger.
This patent application is currently assigned to CREARE, INC.. Invention is credited to Weibo Chen, Michael G. Izenson.
Application Number | 20100132930 12/598114 |
Document ID | / |
Family ID | 40341955 |
Filed Date | 2010-06-03 |
United States Patent
Application |
20100132930 |
Kind Code |
A1 |
Izenson; Michael G. ; et
al. |
June 3, 2010 |
Flexible Heat/Mass Exchanger
Abstract
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.
Inventors: |
Izenson; Michael G.;
(Hanover, NH) ; Chen; Weibo; (Hanover,
NH) |
Correspondence
Address: |
DOWNS RACHLIN MARTIN PLLC
199 MAIN STREET, P O BOX 190
BURLINGTON
VT
05402-0190
US
|
Assignee: |
CREARE, INC.
Hanover
NH
|
Family ID: |
40341955 |
Appl. No.: |
12/598114 |
Filed: |
May 2, 2008 |
PCT Filed: |
May 2, 2008 |
PCT NO: |
PCT/US08/62478 |
371 Date: |
October 29, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60915558 |
May 2, 2007 |
|
|
|
Current U.S.
Class: |
165/168 ;
165/173 |
Current CPC
Class: |
A41D 13/0053 20130101;
F28D 21/0015 20130101; F28F 3/086 20130101; F28F 2255/02 20130101;
F28F 3/12 20130101; F28F 21/065 20130101; F28D 5/00 20130101 |
Class at
Publication: |
165/168 ;
165/173 |
International
Class: |
F28F 3/12 20060101
F28F003/12; F28F 9/02 20060101 F28F009/02 |
Goverment Interests
STATEMENT OF GOVERNMENT INTEREST
[0002] Subject 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.
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.
Description
RELATED APPLICATION DATA
[0001] 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.
FIELD OF THE INVENTION
[0003] The 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.
BACKGROUND
[0004] There 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.
[0005] 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 DISCLOSURE
[0006] In 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.
[0007] 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.
[0008] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] 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:
[0010] FIG. 1 is a schematized cross-sectional view of a heat/mass
exchanger made in accordance with concepts of the present
disclosure;
[0011] FIG. 2 is a graph of temperature versus time for an example
heat/mass exchanger made in accordance with the present disclosure,
illustrating the cooling performance of the heat/mass exchanger at
various flow rates and with and without an evaporation-assisting
fan;
[0012] FIG. 3A is an isometric exploded view of a four-layer
rectangular laminate heat/mass exchanger made in accordance with
concepts of the present disclosure;
[0013] FIG. 3B is a plan view of the two inner layers of FIG. 3A
placed side-by-side;
[0014] FIG. 3C is a plan view of the two inner layers of FIG. 3A
one superimposed on the other;
[0015] FIG. 4 is an isometric exploded view of another four-layer
heat/mass exchanger made in accordance with concepts of the present
disclosure that is flexible in any direction;
[0016] FIG. 5 is a perspective view of a personal hydration system
having a cooling system that includes a heat/mass exchanger similar
to the heat/mass exchanger of FIG. 4;
[0017] FIG. 6A is a plan view of a flow matrix structure that
includes elongated depressions in opposing faces of adjacent layers
oriented substantially perpendicularly to each other;
[0018] FIG. 6B is a cross-sectional view as taken along line 6B-6B
of FIG. 6A;
[0019] FIG. 7A is a plan view of an alternative flow matrix
structure having circular depressions that extend inwardly from
opposing faces of adjacent layers;
[0020] FIG. 7B is a cross-sectional view as taken along line 7B-7B
of FIG. 7A;
[0021] FIG. 8 is a plan view of yet another flow matrix structure
for a four-layer exchanger formed by overlapping two patterns of
circular holes cut in two separate layers;
[0022] FIG. 9 is a plan diagrammatic view of another alternative
flow matrix structure formed by joining adjacent layers in a manner
to direct fluid flow through the flow matrix in a serpentine
pattern;
[0023] FIG. 10 is a partial perspective view/partial diagrammatic
view of a personal evaporative cooling system having exchangers
made in accordance with concepts of the present disclosure;
[0024] FIG. 11 is a plan view of the cooling module of FIG. 10 with
the cover removed to expose the internal components to view;
[0025] FIG. 12 is a cross-sectional view as taken along line 12-12
of FIG. 11; and
[0026] FIG. 13 is a perspective view of an evaporative cooling
system made in accordance with concepts of the present
disclosure.
DETAILED DESCRIPTION OF THE DRAWINGS
[0027] Referring now to the drawings, FIG. 1 illustrates a
heat/mass exchanger 100 made in accordance with concepts of the
present disclosure. At a high level, heat/mass exchanger 100 has
first and second outer faces 104, 108 spaced from one another, with
a flow channel 112 located between the first and second outer
faces. As will be discussed below in detail, exemplary heat/mass
exchanger 100 includes a number of beneficial features, including a
resilient highly flexible construction (e.g., it can be folded back
on itself without permanent deformation), a permeable construction
that allows for mass transfer from fluid in the flow channel 112
through either or both of the first and second outer faces
(depending on the location(s) of permeable material) to a cooling
medium outside the exchanger, and fabrication materials and
techniques that favor creation of integral design features such as
either or both of an inlet manifold 116 and outlet manifold 120
placed adjacent to the flow channel 112. In addition, although not
explicitly shown in FIG. 1 but explained in more detail below, flow
channel 112 may be configured for highly efficient heat and/or mass
transfer across a large extent of the expanse of the flow matrix,
i.e., both along the "length" of the flow channel between inlet and
outlet manifolds 116, 120 and along the "width" of the flow channel
in a direction perpendicular to the length.
[0028] 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 FIGS. 3A-C, 4, and 6A-9. It is noted that
while heat/mass exchanger 100 includes all of these features, those
skilled in the art will readily understand that other embodiments
of a heat/mass exchanger made in accordance with the present
disclosure does not need to include all of these features, but
rather may include only one or two of these features.
[0029] 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 FIG. 1 as a discrete layer relative to the others
so as to suggest that each layer consists of a single sheet of
material, this need not necessarily be so. For example, in various
embodiments, each layer 124, 128, 132 may comprise one, two or
three or more sheets. Alternatively, regarding intermediate layer
132, this layer may not include any discrete sheets at all, but
rather may be formed from portions of sheets that make up the first
and/or second outer layers. In an extreme example (albeit one that
would likely be challenging to manufacture but nonetheless
possible), heat/mass exchanger 100 could be made of a single sheet
of material, and layers 124, 128, 132 in this context would
correspond to "zones" within the single sheet. At the other
extreme, examples could be made where a plurality of internal
layers 132, each created by one or more sheets or by portions of
adjacent sheets, are used to construct the flow channel 112.
Specific examples of heat/mass exchangers of the present disclosure
having two- and four-sheet laminated construction are shown and
described below in connection with FIGS. 3A-C, 4, 6A-9.
[0030] 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.
[0031] 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.
[0032] 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 FIG. 1, but see 3A-C, 4, 6A-B, 7A-B, 8 and
9) formed in intermediate layer 132 that allow fluid contact with
outer layers 124, 128 bounding the flow matrix, thereby permitting
mass transfer to one or both of first and second outer faces 104,
108. It is noted that in the embodiments shown in FIGS. 3A-C, 4,
6A-B, 7A-B, 8 and 9 the flow matrices that each provide flow
channel 112 to the respective heat/mass exchanger are defined by
sheets of material provided with various openings, depressions or
other structures when the sheets are overlain with one another. In
other embodiments, the structure of flow matrix may be provided in
other ways, such as using a sheet of fibrous material formed into a
three-dimensional matrix. In yet other embodiments, flow channel
112 may simply be a single passageway without any sort of flow
matrix structure. In differing embodiments, possible materials
composing the heat/mass exchanger include urethane, polyimide,
nylon, and others. When flexibility is not needed, thin metal
sheets can also be used to assemble intermediate layer 132.
Typically, though not necessarily, the intermediate layer will have
a thickness in the range 0.025 mm to 1 mm.
[0033] 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 FIG. 1, may
be molded to conform to the shape of the outer surface of a
military personnel combat helmet. During use, the molded heat/mass
exchanger would be secured to the outer surface of the helmet with
a permeable outer layer facing outward. Mass transfer of a working
liquid, e.g., water, through the permeable layer would provide
evaporative cooling as described below, thereby providing cooling
to the helmet and relief to the wearer.
[0034] When: 1) a liquid working fluid (represented in FIG. 1 by
arrows 136) resides in or passes through the flow channel 112 in a
cooling mode; 2) first outer layer 124 is permeable and second
outer layer 128 is impermeable to the working liquid and its vapor
and 3) heat/mass exchanger 100 is located in an ambient air
environment 144 that is not saturated with the vapor phase of the
working fluid, the heat/mass exchanger works as follows. Working
liquid 136, such as water to be cooled for personal hydration,
flows into inlet manifold 116, for example, via an inlet fluid port
140. Manifold 116 delivers working liquid 136 to flow channel 112
and distributes it substantially evenly across the width of the
flow matrix. Because the ambient air 144 is not saturated with
vapor, there is a difference in chemical potential that favors mass
transfer from the working fluid to the ambient air. As working
fluid 136 flows through flow channel 112, a very small fraction of
fluid will transfer through the permeable outer layer 124 and enter
the surrounding air 144 as vapor. Substantial heat is absorbed in
this process by evaporation of the working fluid. Heat needed to
drive this evaporation is drawn from the working fluid and the
surrounding air.
[0035] 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 FIG. 2, which contains a graph 200 of data
collected using a working example of a heat/mass exchanger made in
accordance with the present disclosure. For context, this working
example was a 15 in. (38.1 cm).times.8 in. (20.3 cm) rectangular
heat exchanger constructed in the manner of heat exchanger 300 of
FIG. 3A, wherein the thickness of the outer layers was on the order
of 125 .mu.m (0.005 inches).
[0036] Referring now to FIG. 2, and also to FIGS. 1 and 3A, FIG. 2
contains a graph 200 illustrating the performance of a heat/mass
exchanger having the general configuration of heat/mass exchanger
300 of FIG. 3A. In this working example, heat/mass exchanger 300
had a working liquid of water passing through flow channel 112.
First and second outer layers 124, 128 (corresponding to first and
second outer sheets 304, 308 of FIG. 3A) were constructed of ePTFE
porous polymer membranes. Intermediate layer 132 (which corresponds
to the composite formed by first and second intermediate sheets
312, 316 of FIG. 3A-C) incorporating flow channel 112 was
constructed of a pair of urethane sheets, each sheet containing a
diagonal pattern of parallel channels 320, 324 fully penetrating
the sheet thickness as shown in FIG. 3B. Two such sheets were
overlain with one another so that parallel channels 320 in each
intermediate sheet 312, 316 run along opposite diagonals, creating
a crisscrossing pattern of interconnected flow channels that
constitute the flow channel 112. The porosity of the ePTFE material
in each of first and second outer layer 124, 128 (first and second
outer sheets 304, 308 of FIG. 3A) permitted a portion of the water
from flow channel 112 to migrate to some part of each of first and
second outer faces 104, 108 where unsaturated ambient air induced
evaporative cooling at the two outer faces. The water was thereby
cooled by conduction through the flexible laminate structure of
heat exchanger 300, which in turn was cooled by evaporative cooling
at first and second outer faces 104, 108.
[0037] Referring to FIG. 2 in greater detail, graph 200 displays
the ambient air temperature 204, water inlet temperature 208, and
water outlet temperature 212 as a function of time for an
embodiment similar to that shown in FIG. 3A as operational
conditions were varied. Before any flow through the exchanger
(until approximately 10 minutes into the test), all three
temperatures 204, 208, 212 were approximately the same (70.degree.
F.-72.degree. F.). The relative humidity of the ambient air was
such that the wet bulb temperature was 51.degree. F., which would
be the lowest achievable fluid temperature at equilibrium. When
water flow through the exchanger began at approximately 10 minutes,
the water cooled to an outlet temperature 212 of about 63.degree.
F. by natural convection with the surrounding air. When the
velocity of the ambient air 144 across the outer faces (104, 108 in
FIG. 1) was increased by starting a fan at 25 minutes, evaporative
cooling was enhanced by forced convection, resulting in increased
cooling of the water (working liquid). This is evident in graph 200
by the drop in water outlet temperature 212 from approximately
63.degree. F. at time t=25 minutes, to approximately 55.degree. F.
when the fan is turned on. Water outlet temperature 212 does not
reach the wet bulb temperature, suggesting insufficient area to
completely reach equilibrium. As the working liquid flow rate was
increased from 1.8 L/hr to 3.3 L/hr at approximately t=90 minutes,
the residence time of the working liquid decreases and the volume
of fluid that must be cooled in a given time increases. As a
result, the outlet temperature of the working fluid 136 rose
slightly, to approximately 57.degree. F. An apparatus without the
ability to utilize a portion of the working liquid for evaporative
cooling would have been unable to achieve exit working liquid
temperatures lower than the ambient air temperature.
[0038] The embodiment shown in FIG. 1 has been described in terms
of heat/mass transfer that involves cooling of the working fluid
136 in conjunction with transport and evaporation of working fluid
from the first or second outer faces 104, 108 into the ambient air
144. It should be recognized that this process may be reversed,
using a chemical potential gradient to transport moisture from the
ambient air 144 and into the working fluid 136. This
dehumidification process requires that the external layers 124, 128
have the same properties for transporting fluid (in liquid or vapor
form) as are utilized in the evaporation mode. Various chemical and
physical means for controlling the chemical potential gradient are
well known in the engineering arts.
[0039] In addition, while channel 112 of exemplary heat/mass
exchanger 100 of FIG. 1 is denoted as a "flow channel," it should
be appreciated that working fluid 136 does not need to be moving to
be cooled. For example, when working fluid 136 is not moving,
channel 112 may be considered a reservoir. In this case, the
stagnant working fluid 136 is cooled by the same evaporative effect
described above. An example of a useful device in which channel 112
intermittently acts as a reservoir for stagnant working fluid 136
is described below in the context of personal hydration system 500
of FIG. 5.
[0040] Referring now to FIGS. 3A-C, FIG. 3A illustrates an
exemplary heat/mass exchanger 300 having the basic configuration of
heat/mass exchanger 100 of FIG. 1 executed with a four-sheet
construction that includes first and second outer sheets 304, 308
and first and second intermediate sheets 312, 316. Comparing
heat/mass exchanger 300 of FIG. 3A to diagrammatic heat/mass
exchanger 100 of FIG. 1, it is seen that first and second outer
sheets 304, 308 correspond, respectively, to first and second outer
layers 124, 128, and first and second intermediate sheets 312, 316
together correspond to intermediate layer 132. For additional
clarity, FIG. 3B shows intermediate sheets 312, 316 oriented as
they would be when overlain with one another in the assembled
heat/mass exchanger 300, with first sheet 312 containing a diagonal
pattern of parallel channels 320 fully penetrating the sheet
thickness, and second sheet 316 containing a complementary diagonal
pattern of parallel channels 324 fully penetrating the sheet
thickness. The flow matrix (112 in FIG. 1) is constructed by
overlaying the two intermediate sheets 312, 316 so that parallel
channels 320, 324 in corresponding respective sheets run on
opposite diagonals, creating a crisscrossing pattern of
interconnected flow channels that constitute the flow matrix. This
aspect of the embodiment is perhaps best illustrated in FIG. 3C.
Channels 320, 324 may be created in intermediate sheets 312, 316 by
means well known to those practiced in the arts, such as by
mechanical or laser cutting a finished sheet or in the sheet
manufacturing process by molding or casting techniques. FIG. 3B
illustrates a case in which intermediate sheets 312, 316 are
actually the same design rotated and flipped in two different
orientations. However the intermediate sheets 312, 316 can be
patterned with different designs as well, depending on the specific
requirements for the exchanger.
[0041] 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 FIG. 4.
[0042] In the example shown in FIG. 3A, first and second outer
sheets 304, 308 each include corresponding respective openings
304A-B, 308A-B provided to receive therethrough corresponding ones
of inlet/outlet fluid ports 336, 340 and inlet/outlet manifolds
328, 332 formed in intermediate sheets 312, 316. It is noted that
in alternative embodiments, any one or more of openings 304A-B,
308A-B need not be provided. For example, in some other
embodiments, first outer sheet 304 may be continuous over
inlet/outlet manifold 328 and include an embossment (not shown)
that conformally receives therein that inlet/outlet manifold, and
likewise, second outer sheet may be continuous over inlet/outlet
manifold 332 and include an embossment (not shown) that conformally
receives therein that inlet/outlet manifold. In yet other
embodiments, the inlet/outlet manifolds may be defined by
corresponding respective embossments or like structures (similar to
manifolds 328, 332) formed in corresponding respective ones of the
first and second outer sheets rather than in the first and second
intermediate sheets.
[0043] 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 FIG. 1) from
thin flexible sheets as done in heat/mass exchanger 300 of FIGS.
3A-C can create concerns with ballooning of the heat/mass exchanger
in the region of the flow matrix under pressure of the flowing
working liquid. This is overcome by implementing any one or more of
various techniques for joining, adhering, or otherwise sealingly
securing sheets 304, 308, 312, 316 at points of contact with
adjacent sheets, for example, adhesive bonding, thermal bonding,
sonic welding, or other similar technologies appropriate for the
particular materials of construction used. The same or similar
techniques may be used to fluidly seal the various sheets 304, 308,
312, 316 of heat/mass exchanger 300 to one another around the
perimeter of the flow matrix so as to laterally define the flow
matrix.
[0044] FIG. 4 illustrates another exemplary heat/mass exchanger 400
having the basic configuration of heat/mass exchanger 100 of FIG. 1
and executed with a four-sheet construction in a manner similar to
heat/mass exchanger 300 of FIGS. 3A-C. In particular and relating
heat/mass exchanger 400 to heat/mass exchanger 100 of FIG. 1,
heat/mass exchanger 400 includes first and second outer sheets 404,
408 that correspond, respectively, to first and second outer layers
124, 128 of FIG. 1 and first and second intermediate sheets 412,
416 that together correspond to intermediate layer 132 of FIG. 1.
Flow channel 112 of FIG. 1 is generally formed from the two
intermediate sheets 412, 416, each of which has diagonal cutouts
420 and that are overlain with one another in a manner to cause the
cutouts portions of the sheets to intersect in a crisscross
pattern.
[0045] In contrast to heat/mass exchanger 300 of FIG. 3A-C, each
fluid inlet/outlet port 424 of heat/mass exchanger 400 of FIG. 4
(only one visible in FIG. 4) is centrally located relative to a
corresponding one of a pair of inlet/outlet flow manifolds 428,
432. Both fluid inlet/outlet ports 424 in this example are provided
in second outer sheet 404. First outer sheet 408 includes a pair of
recesses 436, 440 that accommodate corresponding respective
inlet/outlet flow manifolds 428, 432, which are generally formed in
first intermediate sheet 412. Depending on the materials of
construction, recesses 436, 440 may be specifically formed, for
example, by molding or embossing, or, if first outer sheet 408 is
essentially flat and sufficiently flexible, may simply be an
artifact of laying the first outer sheet over inlet/outlet
manifolds 428, 432 that are relatively rigidly formed in first
intermediate sheet 412. Second interior sheet 416 includes a pair
of openings 444 (only one visible in FIG. 4) for allowing fluid
communication between inlet/outlet flow manifolds 428, 432 and
corresponding respective ones of fluid inlet/outlet ports 424
(again, only one is visible in FIG. 4). In this example, each of
the four corners of heat/mass exchanger 400 is provided with an
attachment point 448, 452, 456, 460 for securing the heat/mass
exchanger to some other structure. FIG. 5 illustrates one example
of utilization of attachment points 448, 452, 456, 460 in which
heat/mass exchanger 400 of FIG. 4 is secured to a hydration pack
500 via the attachment points to form an integrated personal
hydration system 504. The materials of sheets 404, 408, 412, 416
may be the same as the materials described above for layers 124,
128, 132 of heat/mass exchanger 100 of FIG. 1.
[0046] Referring now to FIG. 5, hydration pack 500 provides a
reservoir for potable water for drinking by a user (not shown) of
personal hydration system 504. Hydration pack 500 can be any
conventional or custom pack adapted for supporting or otherwise
integrating heat/mass exchanger 400 and for fluidly communicating
the potable water to and from the heat/mass exchanger. Hydration
system 504 shown includes a handle 508 for hand-carrying and
-wielding, as well as shoulder straps 512 (one visible in FIG. 5)
for allowing the system to be carried on the back of a wearer. In
this example, heat/mass exchanger 400 is secured to hydration pack
500 with a set of four straps 516 and four cinch buckles 520 (only
three of each shown) secured to attachment points 448, 452, 456,
460 (see FIG. 4). Manifolds 428, 432 of FIG. 4 and the
corresponding respective embossments 436, 440 have corrugated
features to afford sufficient flexibility along the width of the
heat/mass exchanger 400 and prevent the manifolds 428, 432 from
being closed off when exchanger 400 is bent in the "width"
direction. It is noted that the curvature of heat/mass exchanger
400 of this example is due to its highly flexible nature, rather
than being molded to this shape (although in alternative
embodiments, the latter could be done, if desired). Regarding the
structure of heat/mass exchanger 400, visible in FIG. 5 is a flow
field region 524 containing the plurality of interconnecting flow
channels of the flow matrix (corresponding to flow channel 112 of
FIG. 1) formed by the oppositely angled cutouts 420 of first and
second intermediate sheets 412, 416 of FIG. 4. Flow field region
524 (FIG. 5) is bounded by a boundary margin 528 where all sheets
404, 408, 412, 416 (FIG. 4) are fluidly sealed to one another to
fluidly seal the flow matrix along the boundary margin.
[0047] Referring again to FIG. 5, heat/mass exchanger 400 is
fluidly coupled to hydration pack 500 by a pair of flexible tubes
(only an upper tube 532 is shown) connected to corresponding
respective ones of inlet/outlet ports 424 (see FIG. 4). In the
setup shown, one of the tubes (not shown) fluidly connects the
lower (relative to FIG. 5) inlet/outlet port 424 of heat/mass
exchanger 400 to the bottom of the reservoir inside hydration pack
500, and upper tube 532 is fluidly connected to the upper
inlet/outlet port 424. A mouthpiece 536, which can be a
conventional hydration-pack-type mouthpiece, is coupled to upper
tube 532. During use of personal hydration system 504, a user,
using mouthpiece 536, draws water from hydration pack 500 through
the lower tube (not shown) and into and through heat/mass exchanger
400, where the water is cooled via the thermal processes and
mechanisms described above relative to graph 200 of FIG. 2, but
without the additional cooling enhanced by the fan. The water then
exits heat/mass exchanger 400 cooler than it entered the heat/mass
exchanger from hydration pack 500, providing the user with water of
a more refreshing temperature. Those skilled in the art will
readily appreciate that many variations of personal hydration and
other liquid systems could be made using the broad underlying
principles disclosed herein.
[0048] 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.
[0049] As seen in FIGS. 3A-C and 4, both heat/mass exchangers 300,
400 shown there have flow matrices formed by two intermediate
layers 312, 316, 412, 416 having corresponding respective channels
320, 324 or cutouts 420 extending along differing diagonal
directions. As those skilled in the art will appreciate, suitable
flow matrices for a heat/mass exchanger made in accordance with
principles and concepts disclosed herein may have any one or more
of a variety of configurations and executions. FIGS. 6A through 9
illustrate a few alternative configurations and executions of flow
matrices to illustrate this variety.
[0050] Referring now to FIGS. 6A-B, these figures illustrate a flow
matrix structure 600 executed in a two-sheet construction
consisting of a first sheet 604 and a second sheet 608 that each
have corresponding respective set 612, 616 of depressions 620
therein that together define the serpentine flow channels 624
within the flow matrix. Flow matrix structure 600 has the
similarity relative to the flow matrices of heat/mass exchangers
300, 400 of FIGS. 3A-C and 4, respectively, of comprising flow
channels 624 formed from elongate spaces that cross one another. A
difference, however, is that flow channels 624 of flow matrix
structure 600 are executed with just two sheets 604, 608 as opposed
to the four sheets 304, 308, 312, 316 or 404, 408, 412, 416 of
heat/mass exchangers 300, 400, respectively. In the present
context, a "depression" is defined as an internal space (relative
to flow matrix structure 600) that extends away from a plane 628
that contains all of the joints where first and second sheets 604,
608 contact one another or are joined to one another. Depending on
the nature of the materials of first and second sheets 604, 608,
which may be made of any of the materials described above relative
to layers 124, 128 of heat/mass exchanger 100 of FIG. 1,
depressions 620 may be, for example, molded into the sheets or
formed by the ballooning of the sheets under positive internal
pressure within flow channels 624 (in such an embodiment the sheets
must be joined to one another at locations other than at the
depressions). As best seen in FIG. 6B, the outer faces 632, 636 of
first and second sheets 604, 608 may follow the contours of
depressions 620 or, alternatively, may be planar, as would be the
case when depressions are provided such that the thickness of each
sheet at locations other than the depressions is greater than the
thickness of that sheet at the depression.
[0051] The views of FIGS. 6A-B show only the relative positions of
depressions 620 and, for the sake of clarity, intentionally omit
other features of an entire heat/mass exchanger that includes flow
matrix structure 600. Those skilled in the art would readily
appreciate how to incorporate such other features as desired upon
reviewing the entire present disclosure. Explicitly comparing the
structure of flow matrix structure 600 of FIGS. 6A-B to the
structure of diagrammatic heat/mass exchanger 100 of FIG. 1, it is
seen that the portions of first and second sheets 604, 608 that
form flow channels 620 and are exposed to the ambient environment
would make up first and second outer layers 124, 128 of heat/mass
exchanger 100 and that the space within flow channels 620
themselves would make up intermediate layer 132 of the heat/mass
exchanger. As discussed above relative to other examples, it should
be clear that one, the other, or both, of first and second sheets
604, 608, or portions thereof, will be permeable so as to provide
flow matrix structure 600 with mass-exchange ability.
[0052] FIGS. 7A-B illustrate another flow matrix structure 700 that
is made of just two sheets (first and second sheets 704, 708) in a
manner similar to flow matrix structure 600 of FIGS. 6A-B. Relating
flow matrix structure 700 of FIGS. 7A-B to flow matrix structure
600 of FIGS. 6A-B, flow matrix structure 700 may be considered to
have "reverse" depressions 712 in each of first and second sheets
704, 708. That is, depressions 712 extend inward relative to flow
matrix structure 700, whereas depressions 620 of FIGS. 6A-B extend
outward relative to flow matrix structure 600. In the embodiment
shown in FIGS. 7A-B, depressions 712 in first sheet 704 are formed
at locations different from the depressions formed in second sheet
708, but with the same height, so that when the first and second
sheets are fastened together (at the depressions), the depressions
on one sheet are staggered relative to the depressions on the other
sheet. Consequently, the "height" of the flow channels 716 formed
among depressions 712 is equal to the height of the depressions. In
alternative embodiments, the depressions may be formed in only one
of sheets 704, 708 and the other sheet remains planar. In yet other
embodiments, the depressions may be formed in both sheets but
located so that when the two sheets are put together, the
depressions of one sheet contact the depressions of the other
sheet. In such embodiments, the "height" of the flow channels
formed amongst the depressions would be the sum of the heights of
each pair of contacting depressions.
[0053] 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 FIGS. 3A-C. The structure of
flow matrix structure 700 corresponds to the three-layer (or zone)
construction of heat/mass exchanger 100 of FIG. 1 in essentially
the same manner as described above relative to flow matrix
structure 600 of FIGS. 6A-B.
[0054] FIG. 8 illustrates another flow matrix structure 800 that
could be utilized in a heat/mass exchanger made in accordance with
concepts disclosed herein, such as heat/mass exchanger 100 of FIG.
1. Flow matrix structure 800 corresponds to flow channel 112 in
FIG. 1 and takes the place of the inner two layers (312, 316 or
412, 416) of the four-layer exchangers 300 and 400 assemblies
described above. In this example, flow matrix structure 800 is
largely defined by overlaying with one another two sheets 804, 808
each containing a two-dimensional array 812, 816 of holes 820 (here
full thickness circular openings). Holes 820 in each array 812, 816
are arranged so that when sheets 804, 808 are overlain, portions of
the holes in one sheet overlap with the holes in the other sheet.
In a finished heat/mass exchanger, flow matrix structure 800 shown
would be sandwiched between first and second outer layers (not
shown, but corresponding to first and second outer layers 124, 128
of heat/mass exchanger 100 of FIG. 1). These outer layers would
contain a working liquid that flows through the holes in flow
matrix 800. The overlapping portions of the holes allow the liquid
to flow through the flow matrix by defining continuous flow
channels 824 through the final structure.
[0055] 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 FIG. 1.
[0056] FIG. 9 illustrates a flow matrix structure 900 in which the
flow matrix 904 (generically denoted by crosshatching) is provided
with a set of flow baffles 908A-D arranged relative to one another
to direct the flow within the flow matrix in a predetermined
manner, here along a generally serpentine path 912. Relating flow
matrix structure 900 to heat/mass exchanger 100 of FIG. 1, it is
noted that first and second outer layers 124, 128 that would bound
flow matrix 904 are omitted from FIG. 9 for clarity and simplicity.
In FIG. 9, flow baffles 908A-D are formed by bonding all layers
together at the locations of the baffles. Those skilled in the art
will readily appreciate that flow matrix 904 may be made in any
suitable manner, such as any one or more of the manners illustrated
in FIGS. 3A-C, 4 and 6A-8. Those skilled in the art will also
appreciate that more or fewer than four baffles may be provided,
that the baffles need not be straight (e.g., they could be curved,
segmented, etc.), and that the baffles may be used to force the
flow along a path that is other than the simple back-and-forth
serpentine path shown. It will also be understood that flow matrix
structure 900 need not be rectangular in shape as shown, but rather
may have any shape desirable to conform to particular design
constraints. This is also true of other flow matrix structures and
entire heat/mass exchangers disclosed herein, such as flow matrix
structures 600, 700, 800 of FIGS. 6A-8 and heat/mass exchangers
300, 400 of FIGS. 3A-5.
[0057] 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 FIGS.
10-12, these figures illustrate a liquid-based personal cooling
system 1000 that includes at least one liquid-cooled garment 1004
and a cooling unit 1008 that together form a liquid/thermal circuit
in which heat gained by the garment from a wearer (not shown) of
the garment is conveyed by a working liquid (e.g., water) to the
cooling unit, where it is given up to the environment. Garment 1004
may be any type of garment, such as a vest, portion of a garment,
or other wearable device, such as a helmet cover and lining,
containing at least one flow channel for conducting the liquid
through the garment and absorbing heat from the wearer.
Liquid-cooled garments suitable for use as garment 1004 are
generally known in the art and, therefore, need not be described in
any more detail herein. The heated liquid from garment 1004 is
conveyed from the garment to cooling unit 1008, via one or more
feed conduits 1012, where it is cooled by a heat/mass transfer
process similar to the heat/mass transfer process described above
relative to FIGS. 1 and 2. After this cooling, the cooled liquid is
returned to garment 1004 via one or more return conduits 1016 so
that it can again be used to absorb heat from the wearer of the
garment.
[0058] As best seen in FIG. 11, the interior of cooling unit 1008
contains one or more heat/mass exchanger assemblies 1100, a liquid
reservoir 1104, a liquid circulation pump 1108, air circulation
fans 1112, and a power supply, here rechargeable batteries 1116. An
electrical charge port 1120 is provided for recharging batteries
1116 when needed. Cooling unit 1008 also includes various conduits
1124, 1128, 1132 and fittings 1136, 1140 for conveying the working
liquid from component to component and connecting the cooling unit
to garment 1004 (FIG. 10). During use, circulation pump 1108 draws
the heated working fluid from garment 1004 (FIG. 10) and forces
fluid through heat/mass exchanger assembly 1100, where the working
liquid is cooled, and then back to the garment to complete the
thermal loop. At the same time, air circulation fans 1112 draw
ambient air into the interior of cooling unit 1008 via an air inlet
1020 (FIG. 10) and across heat/mass exchanger assembly 1100 before
exhausting the air back to the environment via an exhaust outlet
1024 (FIG. 10). The air moving across heat/mass exchanger assembly
1100 enhances evaporation of the working liquid from the outer
surface(s) of the heat/mass exchanger assembly, and may aid in
removing convective heat from cooling unit 1008 (if the ambient
temperature is lower than the cooling fluid's temperature). Liquid
reservoir 1104 stores a makeup supply of the working liquid, for
example, water, to make up for the liquid lost to evaporation
through the mass-exchange cooling process.
[0059] Referring to FIG. 12, in this example heat/mass exchanger
assembly 1100 includes a plurality of parallel, spaced heat/mass
exchangers 1200 fluidly connected at opposite ends to common inlet
and outlet manifolds 1204, 1208. Each heat/mass exchanger 1200 may
be, for example, a mass-transfer-enabled heat exchanger having a
suitable combination of the features described above in connection
with FIGS. 1-9. Parallel heat/mass exchangers 1200 are held in
spaced relation from one another via three multi-slot supports 1212
spaced from one another along the lengths of the heat/mass
exchangers. Providing multiple heat/mass exchangers 1200 in this
manner increases the surface area of heat/mass exchanger assembly
1100 to increase its heat-transfer ability not only by increasing
the surface area available for heat transfer and evaporation, but
also by increasing the flow capacity of the heat/mass exchanger
assembly. In other embodiments, such increases in surface area per
unit volume of a region occupied by a heat/mass exchanger assembly
can be achieved in other ways, such as by pleating a single
sheet-like heat/mass exchanger by creating a plurality of
alternating opposite direction folds or by rolling a large
sheet-like heat/mass exchanger with suitable spacers to provide a
spirally configured heat/mass exchanger assembly, among others.
[0060] 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, FIG. 13 illustrates a heat/mass exchanger assembly 1300
that utilizes a stack 1304 of, in this case, substantially annular
heat/mass exchangers 1308 and a motorized convection fan 1312 to
actively draw air over the surfaces of the heat/mass exchangers to
facilitate cooling. Each heat/mass exchanger 1308 may be, for
example, a mass-transfer-enabled heat exchanger having an
appropriate set of the features described above in connection with
FIGS. 1-9. The multiple heat/mass exchangers 1308 may be considered
to be stacked with one another along a central stacking axis 1316,
though immediately adjacent ones of the heat/mass exchangers are
spaced from one another so that air drawn by fan 1312 is drawn
across the expansive faces of the heat/mass exchangers as indicated
by arrows 1320. Since heat/mass exchangers 1308 are substantially
annular in shape, the inner peripheries 1324 of the heat/mass
exchangers define substantially circular openings 1328.
[0061] 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 FIG.
13). Other embodiments may encompass one or more heat/mass
exchanger units connected and/or formed in helical, cylindrical, or
other useful shapes; pleated or unpleated; have heat/mass exchanger
surfaces having variable orientation to convective air flow or
different orientation than those shown; or may be operated with
steady or intermittent flow of working fluid.
[0062] 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 FIGS.
10-12. In a complete open system, such as the personal hydration
system 504 of FIG. 5, inlet port 1332 would be connected to a
reservoir of liquid desired to be cooled and outlet port 1340 would
provide the cooled liquid to a user of the cooled liquid. Many more
mass/heat exchangers/assemblies and open and closed systems are
possible using the broad underlying concepts of the present
disclosure.
[0063] 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.
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