U.S. patent application number 11/485042 was filed with the patent office on 2006-11-09 for self-cooling container for liquids.
Invention is credited to Gregory J. Kevorkian, Daniel D. Smolko.
Application Number | 20060248910 11/485042 |
Document ID | / |
Family ID | 30119422 |
Filed Date | 2006-11-09 |
United States Patent
Application |
20060248910 |
Kind Code |
A1 |
Smolko; Daniel D. ; et
al. |
November 9, 2006 |
Self-cooling container for liquids
Abstract
Disclosed are self-cooling pouches useful as containers for
beverages and other liquids. Such pouches comprise a porous matrix
as an element of the pouch body to effect the cooling of the pouch
and a liquid contained therein by pervaporation of the liquid.
Inventors: |
Smolko; Daniel D.; (Jamul,
CA) ; Kevorkian; Gregory J.; (Temecula, CA) |
Correspondence
Address: |
G. L. LOOMIS & ASSOCIATES, INC.
990 HIGHLAND DRIVE
SUITE 212Q
SOLANA BEACH
CA
92075
US
|
Family ID: |
30119422 |
Appl. No.: |
11/485042 |
Filed: |
July 11, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10453863 |
Jun 3, 2003 |
7107783 |
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11485042 |
Jul 11, 2006 |
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10162119 |
Jun 3, 2002 |
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11485042 |
Jul 11, 2006 |
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08933639 |
Sep 19, 1997 |
6398048 |
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10162119 |
Jun 3, 2002 |
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60388609 |
Jun 3, 2002 |
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60404355 |
Aug 16, 2002 |
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60458054 |
Mar 25, 2003 |
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Current U.S.
Class: |
62/315 ;
62/457.9 |
Current CPC
Class: |
F25D 2400/26 20130101;
A45F 3/04 20130101; F28D 5/00 20130101; B65D 81/18 20130101; B65D
47/265 20130101; F25D 2331/803 20130101; A47G 21/18 20130101; B65D
51/1616 20130101; A47G 2400/027 20130101; F25D 7/00 20130101; B65D
47/06 20130101; F25D 2331/806 20130101; A61M 2207/00 20130101; A61J
9/04 20130101; A47G 19/2266 20130101; A47G 19/2272 20130101; B65D
2205/00 20130101; B65D 47/242 20130101; F25D 2331/808 20130101;
A41D 13/0053 20130101; A45F 3/18 20130101; B65D 81/3886 20130101;
B65D 1/323 20130101; A45F 3/20 20130101 |
Class at
Publication: |
062/315 ;
062/457.9 |
International
Class: |
F28C 1/00 20060101
F28C001/00; F17C 13/00 20060101 F17C013/00 |
Claims
1. A drinking pouch comprising: a pouch body adapted to act as a
reservoir, comprising one or more walls, wherein at least a portion
of said one or more walls comprises a porous matrix that allows for
the passage of vapor from a liquid contained within the pouch body
such that pervaporation or evaporation of the vapor cools the
liquid contained within the pouch body; and a port through which
the pouch body may be filled with liquid.
2. A drinking pouch according to claim 1 wherein the porous matrix
comprises a membrane.
3. A drinking pouch according to claim 1 wherein the porous matrix
comprises a porous sintered matrix.
4. A drinking pouch according to claim 1 wherein the porous matrix
comprises a laminate comprising a hydrophobic outer layer and an
inner layer which functions as a liquid barrier.
5. A drinking pouch according to claim 4 wherein the hydrophobic
outer layer is pleated.
6. A drinking pouch according to claim 1 further comprising a
drinking tube extending through the pouch body and in fluid
communication with the interior of the pack such that liquid
contained within the body can be consumed through the drinking
tube.
7. A drinking pouch according to claim 6 wherein the drinking tube
further comprises a valved spout.
8. A drinking pouch according to claim 1 wherein said porous matrix
is fabricated from a polymer.
9. A drinking pouch according to claim 1 wherein said porous matrix
is fabricated from polymer selected from the group consisting of
polyethylenes, polypropylenes, ethylene copolymers,
polymethylpentenes, polybutylenes, and blends thereof.
10. A drinking pouch according to claim 1 wherein said porous
matrix is fabricated from a polymer selected from the group
consisting of polytetrafluoroethylene, polyvinylfluoride,
polyvinylidinefluoride, polyethylenetetrafluoroethylene,
fluorinated ethylene propylene, polyperfluoroalkoxyethylene,
polyvinylchloride, chlorinated polyvinylchloride,
polyvinyldichloride and blends thereof.
11. A drinking pouch according to claim 1 wherein said porous
matrix is fabricated from a blend of a fluorinated additive with a
non-fluorinated plastic resin.
12. A drinking pouch according to claim 1 wherein said porous
matrix is fabricated from a silicone polymer or fluorosilicone
polymer.
13. A drinking pouch according to claim 1 wherein said porous
matrix has a thickness of 0.025 to 7.0 mm.
14. A drinking pouch according to claim 1 wherein said porous
matrix has pore size of 0.1 to 100 .mu.m
15. A drinking pouch according to claim 1 wherein said porous
matrix has percent porosity of 10 to 90%.
16. A drinking pouch according to claim 1 wherein said portion of
said one or more walls is 5 to 100% of the total area of said pouch
body.
17. A drinking pouch according to claim 1 wherein said porous
matrix is comprised of hollow or expanded particles, which are
fused or adhered together to reduce the thermal conductivity of the
porous matrix.
18. A drinking pouch according to claim 4 further comprising a
middle layer disposed between the inner layer and the outer
layer.
19. A drinking pouch according to claim 18 wherein the middle layer
comprises a sponge or sponge-like material.
20. A drinking pouch according to claim 1 wherein said porous
matrix comprises a first surface and a second surface and wherein
at least a portion of the first surface is hydrophobic and at least
a portion of the second surface is a hydrophilic.
21. A drinking pouch according to claim 20 wherein the porous
matrix is oriented such that said hydrophobic portion of the first
surface faces the exterior of the pouch body.
22. A drinking pouch according to claim 20 wherein the porous
matrix is oriented such that said hydrophobic portion of said first
surface faces the interior of the pouch body.
23. A drinking pouch according to claim 20 wherein said portion of
said second surface is rendered hydrophilic by a process selected
from the group consisting of plasma etching, chemical etching,
impregnation with wetting agents, and application of hydrophilic
coatings.
24. A drinking pouch according to claim 1 further comprising at
least one strap which functions as a holder for the pouch.
Description
RELATED APPLICATION DATA
[0001] This application is a continuation of U.S. Ser. No.
10/1453,863 which claims priority under 35 U.S.C. .sctn.119(e) to
U.S. Provisional Application Ser. No. 60/1388,609, filed Jun. 3,
2002, and which is also a continuation-in-part of U.S. Ser. No.
10/1162,119, filed Jun. 3, 2002, which is a continuation of U.S.
Ser. No. 08/1933,639 filed Sep. 19, 1997, now US. Pat. No.
6,398,048.
FIELD OF THE INVENTION
[0002] This invention relates to a device and method of
construction of a container or closure used to cool a liquid by
means of pervaporation.
BACKGROUND OF THE RELATED ART
[0003] Evaporative cooling of both dwellings and water originated
in Ancient Egypt and subsequently spread eastward through the
Middle-East and Iran, to the north of India, westward across north
Africa to southern Spain and other regions suffering from a hot and
dry climate. In the initial use of this process non-glazed clay
pots were used for centuries for the storage of water with the
added side benefit of cooling the liquid water contents by
absorbing and wicking the water to the outer clay surface followed
by the evaporation of the water from this surface. Unfortunately,
evaporation directly from the outer clay surface eventually lead to
scale formation and reduced cooling efficiency as the minerals
build up on this surface reducing the liquid permeability and
lowering the liquid vapor pressure.
[0004] Other methods based on heat transfer reduction from the
environment to the liquid have been used. Methods that have been
used include vacuum and air gap thermoses, and foam insulative
jackets. Additional devices using ice, frozen cold packs or sticks
have been used to compensate for heating by surrounding environment
and the return of the liquid in the container to ambient
temperature. In all these cases the design of the system
necessitates that the liquid contents, a separate chamber and/or
the shell of the bottle be cooled leading to excessive weight in
addition to a liquid volume displacement loss in the container. In
all of these methods, the temperature of the liquid will
equilibrate and eventually return to the ambient temperature.
[0005] Pervaporation (PV) is defined as a combination of matrix
vapor permeation and evaporation. From 1987 on, membrane
pervaporation has gained wide acceptance by the chemical industry
for the separation and recovery of liquid mixtures (Chemical
Engineering Progress, pp. 45-52, July 1992). The technique is
characterized by the introduction of a barrier matrix between a
liquid and a gaseous phase. A liquid is in intimate contact with
one side of the matrix. Mass transfer of vapor occurs selectively
to the gas side of the matrix resulting in the loss of liquid or
the loss of select volatile liquid components and the loss of
evaporative latent heat. The process is termed pervaporation
because of the unique combination of vapor "permeation" through the
porous matrix and the liquid to vapor phase change "vaporization".
Without heat added to the liquid, the temperature falls due to the
latent heat of vaporization until an equilibrium temperature is
reached where the heat absorbed from the environment is equal to
the latent heat lost due to liquid evaporation at the matrix
surface or within the pores.
[0006] U.S. Pat. No. 5,946,931 illustrates the use of an
evaporative cooling PTFE membrane device using a stream of fluid in
a laminar flow profile above a membrane in order to cool an
attached device or environment. U.S. Pat. No. 4,824,741 illustrates
the use of a pervaporative cooling matrix to cool the surface of
the plate of an electrochemical cell. The moist plate may be made
from uncatalyzed PTFE-bonded electrode material,a suitable porous
sintered powder, porous fibers, or even a porous polymer film. U.S.
Pat. No. 4,007,601 demonstrates the use of evaporative cooling in a
circulating porous hollow heat exchanger to obtain a cooled
fluid.
SUMMARY OF THE INVENTION
[0007] Disclosed herein is a simplified pervaporative cooling
system for beverage and liquid containers that does not use
mechanical pumps to supply liquid to the pervaporative matrix
surface and does not rely on vacuum to enhance the cooling
efficiency as in the prior art referenced above. A container is
defined as any apparatus or enclosure that holds liquid whether it
is open or closed to the external environment. One embodiment of
this invention utilizes a pervaporative matrix that preferably
forms part of the container body or housing and comprises between 5
to 100% of the total surface area of the container or housing. The
liquid contents of the container are cooled directly at the
surrounding liquid/membrane interface due to the latent heat of
evaporation of the water. The resulting liquid vapor is lost
through the matrix to the surrounding environment or to a collector
or trap such as may comprise an absorbent material. Preferred
containers include bottles, jars, carboys and pouches. The
containers may, in some embodiments, be fabricated into larger
structures, including housings, dispensers, and garments.
[0008] In one embodiment, there is provided a pervaporatively
cooled container, comprising a container body comprising one or
more walls, wherein at least a portion of said one or more walls
comprises a pervaporative matrix, said matrix comprising a porous
hydrophobic material, wherein said matrix allows for the passage of
small quantities of a volatile liquid vapor through the matrix, the
evaporation of which cools the container, including any contents
within the container. In one embodiment, there is provided a
pervaporatively cooled tube or straw, comprising an elongated
hollow tubular structure comprising an outer pervaporative layer
comprising a hydrophobic material coextensive with a porous
internal layer comprising a hydrophilic material, the internal
layer defining a lumen through which a liquid can pass. In one
embodiment, the tubular structure is formed from a hydrophobic
porous tube in which the inner surface of the tube has been
chemically treated to be hydrophilic, thus forming the internal
layer.
[0009] In one embodiment, there is provided a cooling jacket for a
container, comprising a jacket body comprising an outer layer
comprising a hydrophobic porous material; and an inner layer
coextensive with said outer layer and in fluid communication with
said outer layer, said inner layer being adapted to hold a volatile
liquid wherein said jacket body is shaped to allow the inner layer
to contact at least a portion of a container.
[0010] In a preferred embodiment, the containers and cooling
jackets may further comprise a regenerable or disposable outer
layer, directly adjacent to or in contact with the pervaporative
layer, comprising a desiccant, absorbent material or other
substance that absorbs or adsorbs the moisture or other fluid
resulting from pervaporation.
[0011] In one embodiment, there is provided a cooling garment
comprising at least two layers: an outer layer comprising a
pervaporative material comprising a hydrophobic pervaporative
laminate; an optional middle layer comprising a thin support liquid
barrier layer for the pervaporative layer; and an inner layer;
wherein the outer layer is in fluid communication with a body of
coolant liquid, and the inner layer is in thermal contact with the
wearer of the garment. The wearer of the garment is cooled by the
pervaporation of the coolant liquid through the pervaporative
material of the outer layer. In a preferred embodiment, the cooling
garment is incorporated or integrated into a piece of clothing such
as a protective garment or suit. The garment may further comprise a
tube in fluid communication with the body of coolant liquid that
allows the wearer of the garment to orally consume coolant liquid,
preferably water. In a preferred embodiment, the garment further
comprises a regenerable or disposable outer layer comprising a
desiccant or an absorbent material that absorbs the moisture or
other fluid resulting from pervaporation.
[0012] In preferred embodiments, one or more of the following may
also be present: the garment is in thermal contact either by direct
contact with the skin or contact through a piece of fabric or
material, such fabric or material being worn by the wearer of the
garment and/or being part of the garment itself; the outer layer is
pleated to increase surface area for pervaporation; the middle
layer is a barrier to potentially hazardous biological or chemical
materials; and the inner layer comprises patterned or serpentine
regions formed by a heat sealing process.
[0013] In a related embodiment, the garment may further comprise or
be in fluid communication with a reservoir holding additional
coolant liquid. The coolant can be fed into the interstices formed
between the pervaporative matrix and the middle layer from the
reservoir by gravity or by wicking. Preferred coolant liquids
comprise water, alcohols, and blends thereof.
[0014] In related embodiments, containers such as bottles or
backpacks comprising pervaporative material, as described below,
are also provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIGS. 1A and 1B illustrate a bottle in plan and exploded
view in which a generally planar porous matrix may be wrapped a
round or pushed over a bottle body as a cylinder.
[0016] FIG. 2 shows a partially exploded view of a multilayered
structure according to one embodiment comprising a thin membrane
layered between two macroporous layers.
[0017] FIGS. 3A, 3B, 3C and 3D, illustrates plan and cut away views
of embodiments in which support ribs enhance the rigidity of a
porous matrix.
[0018] FIG. 4 shows a container comprising an outer porous
insulative layer. This sleeve reduces direct radiative warming of
the inner bottle surface, yet allows for the pervaporative flux and
loss of latent heat.
[0019] FIG. 5 illustrates one embodiment of container comprising a
pleated matrix that serves as a method for increasing the effective
cooling surface area of the container. This allows for a higher
surface area and quicker liquid cool down time for the
container.
[0020] FIGS. 6A and 6B show one embodiment of a container in plan
and cutaway view comprising an adjustable sleeve to limit the
extent of pervaporative flux and liquid loss from the container.
This sleeve preferably also reduces direct radiative warming of the
inner bottle surface, yet allows for the pervaporative flux and
loss of latent heat.
[0021] FIG. 7 illustrates a cross section of a two-layer
pervaporative sleeve comprising a sponge or sponge-like material
that can be used with a container.
[0022] FIG. 8 shows a cutaway view of another embodiment of
pervaporative cooling jacket that is used on a central housing
containing a liquid, such as a carbonated beverage.
[0023] FIG. 9 is a graph of time versus cooling pertaining to
pervaporative cooling equilibrium using a variety of porous
matrices.
[0024] FIG. 10 illustrates one embodiment of a
pervaporatively-cooled drinking cup.
[0025] FIGS. 11A, 11B and 11C illustrate one embodiment of
pervaporative cooling storage container (e.g. a cooler) having a
pervaporative body shell and pervaporative lid.
[0026] FIG. 12 illustrates a preferred liquid dispensing reservoir
comprising pervaporative matrix.
[0027] FIG. 13 illustrates one embodiment of a hydration backpack
comprising a pleated pervaporatively-cooled reservoir filled with
liquid.
[0028] FIG. 14 illustrates a pervaporatively-cooled drinking pouch
in an optional porous webbed strap-on holder. In addition an
internally wettable pervaporatively-cooled tube is shown, which can
be used for immediately-chilled drinking or dispensing in
connection with the illustrated pouch or with other containers.
[0029] FIG. 15 illustrates a pervaporatively-cooled jacket
according to one embodiment.
[0030] Although the figures illustrate preferred embodiments they
are intended to be merely exemplary and representative of certain
embodiments. To that end, several figures contain optional features
that need not be included in any particular embodiment of the
invention and the shape, type, or particular configuration of
container or closure illustrated should not be taken as limiting on
the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0031] Disclosed herein are containers and enclosures that use
pervaporative cooling to cool a liquid or item residing in such
container or enclosure. In preferred embodiments, the containers
are comprised of porous vent materials, also called porous
matrices. In one embodiment, the container forms part of a
pervaporatively-cooled garment. Porous matrices may be made of any
of a wide variety of materials, including, but not limited to,
plastics, elastomers, metals, glass, and ceramics. Combinations of
plastics, elastomers, metals, glasses, or ceramics may also be
used. The combinations may be intimate, such as from blending of
two or more components to become co-sintered, or may be layered,
such as from laminate structures derived from two or more
materials. Combinations of different plastics, elastomers, metals,
glasses, or ceramics can also be co-sintered or fabricated into
laminate structures for use in pervaporative containers. Preferred
plastics for porous vent materials include, but are not limited to
thermoplastic polymers, thermoset elastomers, and thermoplastic
elastomers. Preferred thermoplastic polymers include, but are not
limited to, low density polyethylene (LDPE), linear low density
polyethylene (LLDPE), medium density polyethylene (MDPE),
high-density polyethylene (HDPE), ultra-high molecular weight
polyethylene (UHMWPE), polypropylene (PP) and its copolymers,
polymethylpentene (PMP), polybutylene terephthalate (PBT);
polyethyleneterephthalate (PET), polyethyleneterephthalate glycol
modified (PETG), polyetheretherketone (PEEK), ethylenevinylacetate
(EVA), polyethylenevinylalcohol (EVOH), polyacetal,
polyacrylonitrile (PAN), poly(acrylonitrile-butadiene-styrene)
(ABS), poly(acrylonitrile-styrene-acrylate (AES),
poly(acrylonirile-ethylene-propylene-styrene) (ASA), polyacrylates,
polymethacrylates, polymethylmethacrylate (PMMA), polyvinylchloride
(PVC), chlorinatedpolyvinylchloride (CPVC), polyvinyldichloride
(PVDC) fluorinated ethylenepropylene (FEP), polyvinylfluoride
(PVF), polyvinylidinefluoride (PVDF), polytetrafluoroethylene
(PTFE), polyester, cellulosics, polyethylenetetrafluoroethylene
(ETFE), polyperfluoroalkoxyethylene (PFA), nylon 6 (N6), polyamide,
polyimide, polycarbonate polyetheretherketone (PEEK), polystyrene
(PS), polysulfone, and polyethersulfone (PES). Preferred thermoset
elastomers include styrenebutadiene, polybutadiene (BR),
ethylene-propylene, acrylonitrile-butadiene (NBR), polyisoprene,
polychloroprene, silicone, fluorosilicone, urethanes, hydrogenated
nitrile rubber (HNBR), polynorborene (PNR), butyl rubber (IIR) to
include chlorobutyl (CIIR) and bromobutyl (BIIR), fluoroelastomers
such as Viton.RTM., Kalrez.RTM., Fluorel.RTM., and chlorosulfonated
polyethylene. Preferred thermoplastic elastomer (TPE) categories
include thermoplastic olefins (TPO) including those commercially
available as Dexflex.RTM. and Indure.RTM.; elastomeric PVC blends
and alloys; styrenic block copolymers (SBC)
includingstyrene-butadiene-styrene (SBS), styrene-isoprene-styrene
(SIS), styrene-ethylene/butylenestyrene (SEBS), and
styrene-ethylene-propylene-styrene (SEPS), some commercially
available SBCs include those sold under the trademarks Kraton.RTM.,
Dynaflex.RTM., and Chronopren.RTM.; thermoplastic vulcanizate (TPV,
also known as dynamically vulcanized alloys) including those
commercially available under the trademarks Versalloy.RTM.,
Santoprene.RTM. and Sarlink.RTM.; thermoplastic polyurethane(TPU)
including those commercially available under the trademarks
ChronoThane.RTM., Versollan.RTM., and Texrin.RTM., copolyester
thermoplastic elastomers (COPE) including those commercially
available as Ecdel.RTM.; and polyether block copolyamide (COPA)
including those commercially available under the trademark
PEBAX.RTM.. Preferred metals for porous materials include stainless
steel, aluminum, zinc, copper and alloys thereof. Preferred glass
and ceramics for porous materials include quartz, borosilicate,
aluminosilicate, sodium aluminosilicate preferably in the form of
sintered particles or fibers derived from said materials.
[0032] A preferred method of making macroporous plastic is by a
process known as sintering, wherein powdered or granular
thermoplastic polymers are subjected to the action of heat and
pressure to cause partial agglomeration of the granules and
formation of a cohesive macroporous sheet or part. The macroporous
material comprises a network of interconnected macropores that form
a random tortuous path through the sheet. Typically, the void
volume or percent porosity of a macroporous sheet is from 30 to 65%
depending on the conditions of sintering although it may be greater
or lesser than the stated range depending on the specific method of
manufacturer. Due to the adjustment of chemical or physical
properties, the surface tension of a macroporous matrix can be
tailored to repel or absorb liquids, but air and vapors can readily
pass through. By example, U.S. Pat. No. 3,051,993 to Goldman,
herein incorporated by reference in its entirety, discloses the
details of making a macroporous plastic from polyethylene. Porous
plastics, including macroporous plastics, suitable for making a
pervaporatively cooled container in accordance with preferred
embodiments, can be manufactured in sheets or molded to
specification and is available for purchase from a number of
sources. Porex Corporation (Fairbum, Ga., U.S.A.) is one such
source, and provides porous plastic under the trademark,
POREX.RTM.. Porous plastic sold under the name POREX.RTM. can be
purchased in sheets or molded to specification from any one of the
thermoplastic polymers previously described. The average porosity
of such POREX.RTM. materials can vary from about 1 to 350 microns
depending on the size of polymer granules used and the conditions
employed during sintering. GenPore.RTM. (Reading, Pa., U.S.A.) is
another manufacturer of porous plastic products, with pore sizes
ranging from 5 t o 1000 microns. MA Industries Inc. (Peachtree
City, Ga., U.S.A.) also manufactures porous plastic products.
Porvair Technology Ltd (Wrexham, North Wales, U.K.) is another
manufacturer of porous products supplying both porous plastic
(range of 5 to 200 .mu.m pore size) under brand name Vyon.RTM. and
porous metal media under the trade name Sinterflo.RTM..
[0033] The basic size, thickness and porosity of the plastic chosen
to make a pervaporative matrix may be determined by calculating the
amount of vapor that must pass through the vent in a given period
of time (flow rate) and the heat transfer rate from the environment
back into the liquid. The flux rate (flow rate per unit area) of a
given macroporous plastic varies depending on factors including the
pore size, percent porosity, and cross sectional thickness of the
matrix and is generally expressed in terms of volume per unit time
per unit area. To achieve a sufficient degree of pervaporative
cooling, the flow rate of vapor through the matrix should be such
that the thermodynamic heat removed from the liquid initially at
room temperature due to vaporization is greater than the heat
absorbed from the environment. During the pervaporative process the
container liquid temperature cools until the heat loss of the
liquid due to vaporization of the liquid contents through the
matrix matches the heat gain from the surrounding environment.
[0034] In common usage, "Macroporosity" generally refers to the
overall void volume of a material or its macrostructure. The term.
"Macroporous" is generally used to classify a material's individual
pores that are considered large. The term "Microporosity" generally
refers to the individual pore sizes or distribution of pore sizes
that constitute the microstructure of a porous material. The term
"Microporous" is generally used to classify a material's individual
pores that are considered small. For purposes of the disclosure
herein, pore size (diameter) is classified according to the
International Union of Pure and Applied Chemistry (IUPAC)
Subcommittee of Macromolecular Terminology, definitions of terms
drafted on Feb. 26, 2002. This standard divides pore size
classification into three categories: Microporous (<0.002mm),
Mesoporous (0.002 to 0.050mm) and Macroporous(>0.050mm). Also
for the purposes of this disclosure herein, void volume will be
discussed in terms of the "Percent Porosity" of the material. Both
macroporous and mesoporous materials, with pore sizes of 0.05 mm or
less, can be used for pervaporative cooling. Preferred methods for
fabrication include casting or stretching membranes of such
materials. Preferred porous materials include those in which the
pores on opposite surfaces (what will become the interior and
exterior surfaces) are interconnected such that the two sides are
in communication with each other. Such interconnections are
preferably not, however, straight through as to create a single
cylindrical tube through which material passes; instead a network
of pores creates a tortuous path.
[0035] For a single layer pervaporative matrix, the porous
materials are preferably macroporous with pore sizes greater than
or equal to 0.05 .mu.m, preferably about 0.1 to 500 .mu.m or about
0.5 to 10 .mu.m including 0.25, 0.5, 1, 5, 15, 20, 40, 60, 80, 100,
150, 200, 250, 300, 350, 400, and 450 .mu.m. In one embodiment the
matrix materials used in conjunction with the pervaporative
containers are between 0.1 and 100 .mu.m preferably between 0.5 and
75 .mu.m. The percent porosity (percent open area) of the materials
are preferably about 10 to 90%, preferably 30 to 75% or 50 to 70%,
including 20%, 40%, 60%, and 80%. The thickness of the porous
materials preferably ranges from 0.025 to 7 mm, including between 1
and 3 mm. Preferred thickness for matrix materials used in
pervaporative containers are about 0.05 to 5 mm and about 0.1 to
3.0 mm, including 0.2, 0.3, 0.5, 0.7, 1.0, 1.25, 1.5, 1.75, 2.0,
and 2.5 mm. Other embodiments may have values for the above
parameters above or below those set forth above. For single layer
matrices, it is preferred that the material be hydrophobic or have
a hydrophobic coating. For the values set forth in this paragraph,
as well as elsewhere in the specification, the stated ranges
include as the values contained between the values specifically
mentioned. In other embodiments, materials can have one or more
properties having values lying outside the disclosed ranges. The
matrix material can be derived from plastic, elastomers, glass,
metal, or combinations thereof. Some preferred matrix materials,
including thermoplastic polymers, thermoset elastomers,
thermoplastic elastomers, metals, glass and ceramics are as
detailed above. Matrix materials may be purchased from commercial
sources, or they may be made according to a variety of techniques.
U.S. Pat. No. 4,076,656 to White et al. details one technique in
which porogens are added to molten or dissolved materials, which
can be leached out with a solvent, or extracted with supercritical
fluids after the material sets and is in its final form. U.S. Pat.
No. 5,262,444 to Rusincovitch et al. details another technique to
create porous material by introducing porogens that evolve into
gases after processing a material, to leave behind a porous
structure. These patents are hereby incorporated by reference in
their entireties.
[0036] Although many pervaporative matrix materials discussed
herein are hydrophobic, Oleophobic pervaporative materials may also
be used when the pervaporation liquid is an organic liquid such as
alcohol. Commodity plastic materials such as nylon, polysulfone,
and the cellulosics are available in hydrophilic grades. These
hydrophilic materials can be milled into particles and sintered
using techniques known to those familiar in the art to produce
hydrophilic porous materials with high liquid flux rates. Porous
hydrophilic plastic, including macroporous plastic can be
manufactured in sheets or molded to specification and is available
f or purchase from a number of sources, including Porex
Corporation. Porous hydrophilic fiber materials can range in pore
size from 20 to 120 .mu.m with percent porosity ranging from 25 to
80 for the pore volume. Moreover, hydrophobia porous materials can
be rendered hydrophilic by one or more treatment processes familiar
to those skilled in the art including, but not limited to, plasma
etching, chemical etching, impregnation with wetting agents, or
application of hydrophilic coatings. In addition, a masking process
can be used in conjunction with one or more treatment processes to
selectively pattern a hydrophobic porous material with regions of
hydrophilicity with high liquid flux rates, if desired. For
example, multilayered porous constructs containing two or more thin
layers of porous material can be laminated to make thicker layers
using techniques familiar to those in the art. Multilayered
constructs may be used to obtain a mechanical and physically
superior matrix as previously observed in our tests. For instance,
combining a sintered macroporous matrix of polyethylene with a thin
layer of expanded PTFE on the liquid side of the container
increases the hydrophobicity and liquid breakthrough pressure of
water from 5 psi to over 30 psi, yet the layered matrix still
maintains a similar pervaporative flux to that obtained using
porous polyethylene alone. Thickness of laminates preferably ranges
from about 0.025 to 7000 .mu.m with average pore sizes, percent
porosity and other properties preferably as described above.
Pervaporative matrix materials may also be derived from porous
materials made from blends. In a preferred embodiment the porous
materials comprise a fluorinated resin including, but not limited
to, polyvinylfluoride (PVF), polyvinylidinefluoride (PVDF),
polytetrafluoroethylene (PTFE), polyethylenetetrafluoroethylene
(ETFE), fluorinated ethylene propylene (FEP),
polyperfluoroalkoxyethylene (PFA) and/or fluorinated additives such
as Zonyl.RTM., blended with selected polyolefin or other resins,
preferably those selected from the series of polyethylenes (LLDPE,
LDPE, MDPE, HDPE, UHMWPE) polypropylene, polyesters,
polycarbonates, ABS, acrylics, styrene polymethylpentene (PMP),
polybutylene terephthalate (PBT); polyethyleneterephthalate (PET),
polyetheretherketone (PEEK), ethylenevinylacetate (EVA),
polyacetal, poly(acrylonitrilebutadiene-styrene) (ABS),
poly(acrylonitrile-styrene-acrylate) (AES),
poly(acrylonirileethylene-propylene-styrene) (ASA), polyesters,
polyacrylates, polymethacrylates, polymethylmethacrylate (PMMA),
polyvinylchloride (PVC), polyvinyldichloride (PVDC), nylon 6 (N6),
polyamide, polyimide, polycarbonate, polystyrene, and
polyethersulfone (PES). Elastomers may also be used alone or in
blends. Preferred elastomers include those of the thermoset type
such as styrene-butadiene, polybutadiene (BR), ethylene-propylene,
acrylonitrile-butadiene (NBR), polyisoprene, polychloroprene,
silicone, fluorosilicone, urethanes, hydrogenated nitrile rubber
(HNBR), polynorborene (PNR), butyl rubber (BR) to include
chlorobutyl (CBR) and bromobutyl (BBR). The resulting blends,
including sintered blends, have porous structures with varying
amounts of porosity, flexibility and mechanical strength determined
predominately from the non-PTFE or other non-fluorinated resin, and
high water intrusion pressures determined predominately from the
fluorinated resin due to its preferential migration to the pore
surface during the sintering process. The percent porosity, pore
size, and thickness are preferably as noted above. Blended matrix
materials may be purchased from commercial sources, or they may be
made according to a variety of techniques. U.S. Pat. No. 5,693,273
to Wolbrom details a process of c0-sintering to produce
multi-porosity porous plastic sheets that can be derived from two
or more polymeric resin materials and U.S. Pat. No. 5,804,074 to
Takiguchi et al. details a process to produce a plastic filter by
co-sintering two or more polymeric resins in a molding process to
produce filter parts. Both of these patents are hereby incorporated
by reference into this disclosure in their entirety.
[0037] In preferred embodiments, a simplified pervaporative cooling
system for containers is presented that does not use any mechanical
pumps to supply liquid to the pervaporative matrix surface and does
not rely on vacuum to enhance the cooling efficiency. The present
approach utilizes a pervaporative matrix that forms part of the
container, preferably the housing of the container, and comprises
between about 5 to 100% of the total surface area of the container,
including about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% of
the total surface area. The liquid contents of the container are
preferably cooled directly at the surrounding liquid matrix
interface due to the latent heat of evaporation of the liquid, such
as water or a water/dissolved solid mixture or solution, in the
container. In an alternate embodiment, a pervaporative sleeve or
housing is used to cool a body such as a drinking vessel or
container in contact with the sleeve. The resulting liquid vapor is
lost to the surrounding environment or to an absorbent material
through the matrix. In most containers, natural convection and
conductive heat transfer within the liquid are predominant heat
transfer mechanisms responsible for cooling the liquid contents of
the container. Depending upon the dimensions and other properties
of the container, the cooling may be substantially uniform
throughout the container.
[0038] The liquid content of the pervaporative container or sleeve
acts as a coolant. Preferably the liquid volume loss is marginal;
for example, in one embodiment, the liquid volume loss of
approximately 15% over a 24 hour time period even with significant
external air circulation. Due to the high latent heat of
vaporization of water (583 cal/g at 75.degree. F.), for example,
approximately seven times as much weight in ice would be required
to maintain the same temperature drop as a loss of water due to
vaporization. An added benefit of the porous matrix in addition to
pervaporative cooling is in venting any pressure differential
developed in the container due to the release of carbonation from a
beverage or due to the consumption of the contents.
[0039] Referring now to the drawings, there is shown in FIGS. 1A
and 1B one embodiment of a vented pervaporative-cooling container
formed in accordance with this invention. The wall 501 of the
container is formed at least in part of pervaporative matrix. This
vapor permeable matrix can be from about 5 to 100% of the total
surface area of the container. Approximately 100% coverage is
achieved if the entire cap and housing (comprising the top 500
walls 501 and bottom 502) are made from porous matrix material. In
one preferred embodiment, the pervaporative surface area is greater
than about 30% of the total container surface and provides a
substantial amount of pervaporative flux to effectively cool the
contained liquid below ambient temperature and maintain a
sub-ambient liquid temperature.
[0040] In one embodiment, as shown in FIG. 2, a multilayered
construct comprising two or more layers may be used. In one
embodiment, three layers of porous material 503, 504 and 505 are
used to obtain a multilayer or laminate matrix. In one embodiment,
a sintered macroporous matrix of polyethylene 505 with a thin layer
of expanded PTFE 504 on the liquid side of the container increases
the hydrophobicity and liquid intrusion pressure but helps to
maintain a similar pervaporative flux and good mechanical stability
as is obtained using porous polyethylene alone. In addition, a
third layer of porous polyethylene 503 forming a sandwich with the
expanded PTFE in the middle 504 provides a scratch resistance
surface close to the inside of the container making it dishwasher
safe and substantially preventing or reducing the soft expanded
PTFE layer from being damaged. In related embodiments, laminates
can comprise greater or fewer than three layers and/or different
porous matrix materials.
[0041] In an alternate embodiment, the inner layer 503 comprises a
pervaporative matrix or laminated matrix, middle layer 504
comprises a thermally insulative material with pores or other open
spaces to allow passage of the vapor, and outer layer 505 comprises
a desiccant or absorbent material.
[0042] In a preferred orientation of the matrix, membrane with a
higher liquid intrusion faces the inside of the container and the
porous matrix support is exposed to the air outside of the
container. Thicknesses for these porous materials in a preferred
embodiment are in the range from about 0.001'' (0.025 mm) to 0.25''
(6.4 mm). The porous matrices can also provide structural rigidity,
scratch resistance, and/or mechanical integrity to the walls of the
container.
[0043] In a preferred embodiment, a membrane or thin layer of
material with a small pore size (<10 .mu.m) can be selected from
a group of highly hydrophobia materials such as expanded
polytetrafuoroethylene (ePTFE) and laminated in between thicker
highly porous supports such as sintered polyethylene, which allow
for a substantial pervaporative flux. If only two layers are used,
each of these layers can vary in thickness from a monoatomic
surface treatment to 1/4'' (6.4 mm) in thickness or greater for a
foam insulation or porous composite. Porous ceramic materials
including molecular sieves (zeolites) or porous polymer films (CSP
Technologies; Auburn, Ala.) and organic matrices such as activated
carbon can be used to substantially prevent or reduce odors from
the environment from contaminating the liquid contents of the
pervaporative cooling device or container.
[0044] In a preferred embodiment, a layered construct comprises
five layers: an inner ePTFE layer, a porous polypropylene, a
thermally insulative urethane foam layer, a ceramic such as zeolite
and a thin nonporous polyolefin or polyester outer wrap. This
device can be used to maintain a pervaporative cool within the
device in a humid environment. Upon absorption of the vapor
released from the liquid, the zeolite or other desiccant transfers
the heat directly or indirectly into the environment while the
insulated liquid contents within the pervaporative sleeve are
cooled. The outer two layers comprising zeolite and a nonporous
film may be disposable or regenerable such as by drying in an
oven.
[0045] Except for any surface treatments that may be applied
directly to the porous matrices in the constructs, the porosities
of the matrices or composite are preferably maintained between
about 10 to 95%. This provides for structural support within the
matrix and enhances the available pervaporative surface area and
hence the overall cooling rate of the container. The pore size of
the matrix can also have an effect with Knudsen diffusion
Predominating below a pore size of 200 nm effectively decreasing
the vapor permeation rate and extending the liquid t o vapor
transition and cooling zone to the air/vapor surface of the
material. In accordance with one embodiment preferred pore sizes
include those between about 0.5 .mu.m to 30 .mu.m, which is larger
than the Knudsen diffusion range. The liquid intrusion pressure
decreases substantially above a 100 .mu.m pore size, making the use
of a single layer of macroporous material less desirable in some
instances. If a combination of a membrane and a macroporous support
are used, then larger pore sizes in the macroporous support become
more desirable than in the absence of the combination.
[0046] As shown in FIGS. 3A, 3B, 3C, and 3D ribs 508 and 514 may be
added to the inside and/or outside walls of the container to
enhance the structural rigidity of the container, prevent or reduce
damage to the pervaporative matrix 507 and 513 and/or provide a
handhold 514. FIGS. 3C and 3F show a sports version of the ribbed
design with a narrowed neck 512.
[0047] The embodiment in FIG. 4 comprises a layer of open cell
porous insulator 518 may be added to the outside surface of the
container to allow for relatively unimpeded vapor diffusion out of
the system but reduced convective and radiative heat flow from the
surrounding environment through to the inner container walls 517
and into the liquid. A beneficial feature of this insulator 518 is
that it aides as an additional structural support, provides a
hand-grip on the container, and reduces or prevent damage to the
matrix 517. As used herein, "pleated" includes rippled surfaces and
other configurations for increasing surface area. Pleated matrices
include those, in which the entire surface is pleated, or in which
one or more portions are pleated and others are left smooth.
[0048] Use of a pleated membrane or pleated porous sintered matrix
520, as shown in FIG. 5, can enhance the pervaporative cooling of
the container since the rate of pervaporative cooling is a direct
function of the surface area of the container.
[0049] Pervaporative containers and garments may comprise an
adjustable or movable sleeve on the outside of the pervaporative
matrix to allow for selective covering or uncovering of some or all
of the pervaporative material. Covering some of the pervaporative
material reduces the vapor flux rate is while still maintaining
some pervaporative cool. Covering all of the pervaporative material
substantially stops the pervaporation and can serve as a type of
"on-off" switch for the container or garment.
[0050] For example, sleeves 524 and 525, as shown in FIGS. 6A and
6B can be provided as a means to reduce the exposed porous surface
area 527 and overall evaporative cooling rate of the container and
hence reduce the liquid vaporization rate and cooling rate allowing
for greater control of the temperature of the container contents.
Reduced cooling may be desired in some situations such as when the
absolute pressure, relative humidity and/or ambient temperature are
low. As shown in FIG. 6B, there is preferably a separation or gap
530 between one or more portions between the container and the
surrounding sleeve. The gap can serve as an insulating region
and/or as a region of buoyant natural convective flow of vapor,
allowing for the maintenance of pervaporative cooling and the
minimization of radiative heat transfer to the liquid contents 529
of the container. The inner sleeve 524 on the outside of the porous
matrix 523 of the container is preferably attached to the
pervaporative matrix at least at the top 522 and bottom 526
portions of the container housing, especially if such portions are
non-porous.
[0051] In one embodiment, some or all of a pervaporative garment or
container may comprise a pervaporative sponge, which both holds
water within the body of the sponge and serves to provide cooling
by pervaporation. One preferred embodiment is a two-layer
pervaporative sponge having an inner sponge comprising a
hydrophilic material and an outer hydrophobic layer attached
thereto. In this configuration, the inner sponge can be soaked with
water or another vaporizable liquid prior t o use and the porous
hydrophobic top layer substantially prevents or reduces the leakage
of the pervaporative liquid at the outer surface of the
pervaporative matrix. The liquid provides a heat transfer path
through the wet matrix directly to the inner container wall
surface.
[0052] FIG. 7 illustrates a two-layer pervaporative sponge 533 that
can be used on glasses, bottles and containers. This configuration
allows the inner sponge layer 534 to be soaked with water or
another vaporizable liquid and a porous hydrophobic top layer 535
substantially prevents or reduces the leakage of the liquid coolant
at the outer surface of the pervaporative matrix 535. The liquid
provides a heat transfer path through the wet matrix directly to
the inner container wall surface 532.
[0053] FIG. 8 shows an alternate configuration in which a cooling
jacket 542 holding water or another pervaporative fluid 541 is
filled through the port 543 and used to cool the contents of an
enclosed container housing 539. The housing comprises one or more
sections of pervaporative matrix 537 and optionally comprises one
or more ribs 538 to enhance structural strength. The liquid
contents 540 within the enclosed central housing 539 can thus be
sealed, substantially preventing or reducing the loss of liquid
volume or carbonation within this region. In addition, the
pervaporative cooling efficiency of the container is not dependent
on the nature of the enclosed liquid; it depends only on the
volatility, heat of vaporization, ionic strength (tonicity) and
solute content of the water or liquid 541 used to fill the
surrounding housing. As shown in FIG. 7 the cooling jacket may also
be made of a detachable sleeve consisting of an outer hydrophobic
pervaporative layer 535 and an inner porous liquid holding or
absorbing layer 534.
[0054] FIG. 10 illustrates a pervaporatively-cooled drinking cup
similar in function to the pervaporative bottles shown in FIGS. 1A,
1B, 2, 3A and 3B. As soon as liquid is poured into the cup the
porous matrix 555 allows the liquid to pervaporatively chill. The
bottle housing and support ribs 556 provide structural support and
insulation.
[0055] These types of cooling jackets 533 and 542 can also be used
in a similar configuration as a food cooler to reduce and maintain
the temperature of the contents 568 below ambient. In one
embodiment, as shown FIGS. 11A, 11B and 11C, baffles 560, 565 and
573 can be used on the cooler to protect the pervaporative matrix
566, and to aide in the mechanical rigidity and handling of the
storage container. Both the lid 558, 572 and bottom 563, 559
portions of the cooler can be filled with water or another
pervaporative liquid 567 and 575 through the liquid fill and drain
ports 561 and 576. The inside of the lid 574 and the bottom 569
portions of the container are preferably made of a nonporous
material.
[0056] FIG. 12 illustrates a chilled water dispenser comprising of
a high capacity water bottle 579, such as a 5 or 10 gallon bottle,
and a pervaporatively chilled liquid dispensing reservoir 580. As
the liquid is replenished in the reservoir 580 from the bottle 579,
the pervaporative matrix 581 surrounding the reservoir chills the
liquid prior to being dispensed from one or more port valves 583.
Alternately, one valve can be used for chilled water and one valve
can be used for hot water. Pervaporative cooling reduces or
eliminates the need for an electrical chilling mechanism such as a
refrigerant compressor. The plastic housing 582 of the reservoir
provides mechanical support for the pervaporative matrix 581.
[0057] In one embodiment, a pervaporative container may comprise
one or more straps to allow the container to be carried on the
body. The container may be worn in any manner, including but not
limited to, being strapped around the torso or a limb or worn in
the form of a backpack or purse. Potential market applications of
this technology fit within the scope of pervaporatively cooled
sports equipment to optimize athlete performance. FIG. 13 shows one
embodiment of a pervaporatively cooled hydration pack 585. The pack
comprises a body 588 comprising pervaporative matrix 591, which in
one embodiment is ribbed to provide greater pervaporative surface
area. The pack is filled with pervaporative fluid through the fill
drain port 587 and can be carried by means of one or more straps
586. A drinking tube 589 is in fluid communication with the
interior of the pack is preferably included to allow the carrier to
conveniently drink the fluid. Pervaporatively-cooled hydration
pack, including backpack-type wearable/carryable containers may be
constructed by forming at least a portion of the bladder component
of any of a variety of hydration packs as are known in the art and
are available commercially (e.g. CamelBak, Petaluma, Calif.;
HydraPak, Berkeley, Calif.) with a pervaporative material such as
by heat sealing, adhesive and/or stitching techniques.
[0058] In one embodiment, a hydration pack 585 comprises a laminate
of at least two layers (1) an outer layer 591 comprising a pleated
or non-pleated pervaporative layer comprising a hydrophobic
pervaporative laminate; (2) a support layer 593 including a
preferably thin support layer for the pervaporative layer 591 which
acts as a liquid barrier. In some embodiments such as for extended
operations, water is fed by gravity or by wicking from a liquid
holding reservoir 588 down into the interstices 592 formed between
the pervaporative matrix 591 and the middle layer 593.
[0059] An optional third layer preferably comprises insulation,
directly touches the skin (or is in thermal contact with the skin
through clothing) and provides a thermal barrier between the user
and the hydration pack. This layer may be continuous or have a
bumped pattern (e.g. fluted, pleated, scalloped) to allow the
passage of air between the user and the hydration pack. An optional
third or fourth layer comprises a desiccant or absorbent
material.
[0060] FIG. 14 shows a pervaporatively-cooled drinking pouch 594 in
an optional webbed strap-on holder 599. The holder may comprise
materials other than webbing; it need only be able to hold the
pouch and preferably not substantially interfere with
pervaporation. A pervaporative pouch such as this can, for example,
be strapped into a belt loop using securing straps 600 or attached
to the side of an existing belt. The webbing 601 allows a free path
for the porous pouch matrix 595 to pervaporate. The pouch 594, in
one preferred embodiment, comprises three main parts: 1) the
pervaporative body 595 comprising a pervaporative matrix, 2) a fill
port 596 and 3) a pervaporatively chilled drinking tube 597, 602
and a valved-spout 598. The body 595 may be made substantially
entirely or in part of pervaporative matrix. The pervaporatively
cooled drinking tube 602, in one embodiment, comprises an outer
pervaporative hydrophobic layer 604, which substantially prevents
or reduces liquid leakage and pervaporative cooling, and an
internal liquid wettable layer 605. Once liquid is introduced
through the center 603 of this layered construct 602 the liquid
penetrates into the hydrophilic material producing a liquid lock
605 which substantially prevents or reduces air form entering the
center of the tube 603 through the porous matrix 604. The liquid
trapped in the hydrophilic matrix 605 is free to pervaporate
through the outer hydrophobic matrix 604. This combination of
hydrophilic 605 and hydrophobic 604 matrices in a tube format 602
provides the benefit of delivering chilled drinking water directly
from the internal tube volume 603 when placed in combination with a
pervaporatively cooled reservoir 594 or with a non-pervaporatively
cooled reservoir, in an alternate embodiment. One simple method of
manufacture of such a device 602 is to plasma treat the center of a
hydrophobic porous PTFE tube. Alternatively, the drinking tube may
be made of non-pervaporative materials.
[0061] In some embodiments, the pervaporative container is in the
form of a lightweight liquid-filled (preferably water-filled)
pervaporative cooling garment that serves as a simple personal
microclimate cooling system to relieve heat stress in individuals
wearing protective clothing, in normal or elevated
ambient-temperature conditions. This type of cooling garment can be
manufactured into protective clothing, such as chemically or
biologically protective suits or Nomex.RTM. fire suits, to form a
part of such clothing or it may be worn in conjunction with such
protective garments. Alternatively, the garment can be worn under a
layer of body armor.
[0062] A cooling garment according to preferred embodiments can be
used for many purposes, including, but not limited to, fire and
rescue personnel, military personnel, and hazardous (chemical
and/or biological) materials workers, as well as for sports
enthusiasts who could increase their endurance by releasing more
heat from their bodies during sporting activities. Pervaporative
garments can also lower the amount of infrared radiation given off
by the wearer. In preferred embodiments, water or combination of
water and ethanol (preferably about 5 to 15%) as a pervaporative
coolant source is used to allow the device to be substantially
non-hazardous and provide an additional functionality such as an
extra pouch for pervaporatively-chilled drinking water for the
wearer. Chilled drinking water can also lessen the heat load on an
individual wearing a protective suit or clothing or engaging in
sporting activities, especially those requiring endurance. Although
non-hazardous and/or potable coolants are preferred, any liquid
capable of providing a pervaporative cooling functionality may be
utilized, including methanol, isopropanol, non-potable water, and
other liquids and solvents. Preferably, the coolant chosen is
compatible with the material(s) it contacts within the garment.
[0063] In one preferred embodiment, a pervaporatively-cooled
garment is in the form of a jacket or vest. The pervaporative
garment may be worn alone or it may be worn incorporated or
integrated in to another article of clothing or garment, such as a
protective suit. When incorporated or integrated into another
garment, the pervaporative garment preferably comprises the
innermost layers to be in close contact (i.e. in thermal contact)
with the wearer. The pervaporatively cooled garment may be in
direct contact with the skin or it may be in contact with other
clothing worn by the wearer. In some embodiments, the pervaporative
garment comprises a layer of fabric or material covering some or
all of the portion of the pervaporative matrix which is directed
toward the inner portion of the garment (i.e. the portion that
touches or is in thermal contact with the wearer).
[0064] Although the discussion regarding pervaporative garments is
in terms of a vest or jacket having a particular configuration,
this discussion should not be construed to limit the disclosed
invention. The principles discussed herein provide for a variety of
pervaporatively cooled garments, including jackets, hats, belts,
pants, leggings, and structures that encase one or more parts of
the body, such as a wrap for a leg or arm (or a portion thereof),
or the neck.
[0065] FIG. 15 shows a design of one preferred embodiment of a
jacket 608. The jacket may be worn alone or the jacket or vest may
be hidden under clothing or protective clothing such as a chemical
suit, Nomex.RTM. fire suit or body armor.
[0066] In a preferred embodiment, the jacket comprises a laminate
of three or four layers: [0067] (1) an optional regenerable or
disposable outer layer 610 comprising a desiccant or an absorbent
material that absorbs the moisture or other fluid resulting from
pervaporation [0068] (2) an outer layer comprising a pervaporative
layer 611, preferably pleated, comprising a pervaporative laminate,
preferably hydrophobic in nature; [0069] (3) a middle layer 613
comprising a thin support layer for the pervaporative layer that
may also act as a liquid barrier, and in some embodiments, a
barrier to potentially hazardous biological or chemical materials.
For extended operations, in one embodiment, water or other cooling
fluid can be fed by gravity or by wicking from a liquid-holding
reservoir 616 such as on the shoulders of the jacket down into the
interstices 612 formed between the pervaporative matrix and the
middle layer; and [0070] (4) an inner layer 615 that is in contact
with the skin, directly or through a piece of fabric or material,
such fabric or material being part of the jacket itself and/or a
separate item worn by the wearer. The inner layer preferably
comprises patterned or serpentine regions formed by a heat-sealing
process. In one embodiment, there is provided a simplified jacket
comprising only layers 2 and 4 above.
[0071] The fluid may be placed in the jacket through the port 607
on the jacket. In a preferred embodiment, the space 614 between the
inner and middle layers forms an air bladder which, when inflated
via a mouthpiece 618, provides insulation from the liquid in the
cooling jacket. When the air bladder is collapsed via the terminal
mouth piece on the air hose, the liquid layer comes into thermal
contact with the skin through the stacking of the middle and inner
layers and this provides on demand cooling. In another embodiment,
a segregated water reservoir in the jacket is sandwiched between
the middle and an inner insulative layer to provide a cool source
of drinking water. Optionally, the reservoir may comprise a
collapsible bag to prevent water from sloshing around which may
create undue or undesirable noise. In other embodiments, the
garment may comprise a drinking tube 617 to allow the wearer to
consume the liquid in the jacket.
[0072] If a pervaporative garment not having an outer
desiccant/absorbent layer is worn under clothing, protective or
otherwise, it is preferred that such clothing be permeable to the
pervaporative fluid or that the clothing have vents, pores or other
openings to allow for passage of the pervaporative fluid.
[0073] In some embodiments, the pervaporative garment further
comprises a regenerable or disposable outer layer comprising a
desiccant or an absorbent material that absorbs the moisture or
other fluid resulting from pervaporation. Suitable desiccants or
absorbent materials for aqueous pervaporative fluid include, but
are not limited to, ammonium sulfate, molecular sieves and
polyacrylic acid. The outer desiccant/absorbent layer can be
discarded following use or it may be regenerated such as by
application of heat and/or reduced pressure. In a preferred
embodiment, the absorbent/desiccant layer absorbs at least about
3-4 times its weight in water. The process of absorbing water in
the layer is preferably endothermic or at least minimally
exothermic. In preferred embodiments, this layer provides a high
degree of absorbency, dimensional stability and/or minimizes
heating due to water vapor hydration in this layer. As will be
readily understood by those skilled in the art, a desiccant or
absorbent layer may be used in combination with any pervaporative
container described herein. When a pervaporative garment of this
type is used in combination with or incorporated or integrated into
another garment, there is no need for pores, vents, openings and
the like in the other garment, although they may be present if
desired. In a related embodiment, at least one surface of the outer
desiccant/absorbent layer comprises a material that is chemically
resistant and/or substantially impervious to chemical and/or
biological agents to provide additional protection to the
wearer.
[0074] The following is brief look at the thermodynamic feasibility
of such a construction. Assuming an average water vapor
pervaporative flux through a porous matrix of 4*10.sup.-6
g*cm.sup.2* s.sup.-1 at 75.degree. F. in still air from Table 1 and
assuming the water vapor flux is doubled at 95.degree. F. gives a
value of 8*10.sup.-6 g *cm.sup.-2*s.sup.-1 for the flux. If the
enthalpy of vaporization at 95.degree. F. is 2400 J/g, the energy
dissipation per unit area of the matrix is 1.9*10.sup.-2
Watts*cm.sup.-2. In order to achieve a power dissipation of 25
Watts, approximately 1500 cm.sup.2 or 1.5 ft.sup.2 of available
matrix surface area must be used in the construction the hydration
pack. Use of a pleated membrane or a pleated porous sintered matrix
to enhance the pervaporative cooling power, since pervaporative
cooling power is a direct function of the porous surface area of
the jacket. In order to cool for 4 hours at this rate approximately
150 mL of water will be spent in the process. Thereby a little
under 0.5 lbs. of water will be used in the process. It would seem
reasonable that a water filled jacket like this may be made to
weigh approximately 3 lbs or less.
[0075] As will be understood by those skilled in the art, the
various layer configurations in the embodiments of jacket, pouch,
and backpack discussed above are interchangeable, as they are
interchangeable with other container configurations disclosed
herein.
[0076] A preferred orientation of multilayer or multifunctional
matrix according to one embodiment is where the higher liquid
intrusion matrix surface faces the inside of the garment and the
matrix supporting backing is exposed to the air outside of the
garment. Thicknesses for these porous materials in a preferred
embodiment are in the range from about 1/128'' (0.2 mm) to 1/8''
(3.2 mm). In one embodiment, layered composites of membranes and
pervaporative matrices are selected to provide both a high liquid
intrusion pressure at the liquid matrix interface using a thin
highly hydrophobic material with a small pore size such as expanded
polytetrafluoroethylene (ePTFE) laminated between thicker highly
porous supports such as sintered polyethylene, which allow for a
substantial pervaporative flux.
[0077] Several processes are available for the manufacture of
pervaporative containers or the pervaporative matrix portion of a
pervaporative garment including, but not limited to, sintering
sub-millimeter size plastic beads in a mold cavity to directly form
the pervaporation wall; thermal or ultrasonic lamination or welding
of one or more pieces of pervaporative matrix together or to a
suitable frame; insert molding whereby one or more sheets or a
cylinder of the porous matrix is inserted into the cavity of a mold
and a thermoplastic polymer is injection molded directly around the
insert(s) to form the desired composite having porous matrix
portions; heat sealing; attaching components using adhesives;
and/or stitching techniques may also be used to assemble all or
part of a pervaporative garment or container.
[0078] Multilayered constructs containing two or more layers of
porous material may be used to obtain a mechanical and physically
superior matrix. For instance, combining a sintered macroporous
matrix of polyethylene with a thin layer of expanded PTFE on the
liquid side of a container increases the hydrophobicity and liquid
breakthrough pressure of water from 5 psi to over 30 psi, yet the
layered matrix still maintains a similar pervaporative flux to that
obtained using porous polyethylene alone.
[0079] FIGS. 1A and 25B show the construction of a preferred
embodiment of a pervaporative container with wall portion 501
comprising pervaporative matrixes. The wall 501 is fixed to the top
500 and bottom 502 portions of the container by a process such as
by insert molding, thermal or ultrasonic welding, adhesive joining,
or other suitable means. Insert injection molding may also be used
to attach the matrix to the other portions of the container. The
top of the bottle 500 illustrated in this example allows for a
threaded fit and can be used with a vented bottle cap. The top 500
and bottom 502 portions of the container may be made by any
suitable method, including injection molding, vacuum forming, and
the like.
[0080] FIGS. 3A and 3B show a ribbed configuration for a thin
pervaporative matrix 507 for which additional structural support
508 is desired. The ribs 508 give the container wall both
structural integrity and a ridged surface for a firmer hand grasp
on the container. The ribs 508 can be placed on the outside, inside
and/or one or more sides of the pervaporative matrix. The ribs 508
are preferably injection molded by insert molding onto the
pervaporative matrix 507. Alternatively, ribs 508 can be sealed to
a porous matrix 507 or porous matrix 507 can be sealed to a ribbed
container shell 508 by ultrasonic, thermal or adhesive means, among
others.
[0081] FIGS. 3C and 3D demonstrate a sports version of this
container, which allows the container to be fixed securely in
a-holding bracket by the bottleneck 512. The mouth of the bottle
511 allows for the use of various closures, including a snap lid
and threaded closure.
[0082] FIG. 4 shows a thermally insulating, hydrophobic open cell
foam layer 518 that allows water vapor to move through the open
cell structure, but impedes the convective and radiative heating of
the container contents. Table 1 demonstrates that the thermally
insulating matrix reduces the liquid loss rate while maintaining a
substantial pervaporative cool. In a preferred embodiment, the
insulating foam 518 is placed or taken off the bottle as an elastic
sleeve.
[0083] Increases in pervaporative cooling efficiency can be
achieved by increasing the surface area of the matrix in contact
with the liquid by pleating the matrix. FIG. 5 shows a pleated
container body 520 that allows a greater pervaporative surface area
to be exposed per contained liquid volume. This configuration
allows for a decrease in the time taken to pervaporatively cool the
container volume. A container having this configuration can be made
by insert molding or by potting both ends with adhesive to a bottom
521 and top 519 container elements or with molten plastic.
[0084] FIGS. 6A and 6B demonstrate a rotating sleeve 525 on the
outside of the matrix body 523. As the outer sleeve 525 rotates
past the inner sleeve 524, a set of vertical slits 527 is formed,
which open and close to allow variable exposure to the
pervaporative matrix 523, thereby reducing the vapor flux rate but
still maintaining an adequate pervaporative cool. A vertical slip
sleeve, whose slits are adjusted vertically instead of by rotation,
may also be used in a configuration of this type. The inner and
outer sleeves 524 and 525 are made of a substantially nonporous
material such as plastic or metal that does not allow water vapor
to pass. FIG. 6B illustrates the annular sleeve that helps to
maintain a very thin gap 530 between the porous matrix 523 and the
inner stationary sleeve 524. This gap 530 is useful as a shield to
substantially prevent or reduce direct conductive and radiative
heat transfer to the porous matrix 523 of the main container body.
In addition, this spacing 530 allows for vapor flux out of this
annular region 527. The sleeves 524 and 525 may also be used over a
pleated pervaporative surface 520 such as shown in FIG. 5. Again,
the sleeves 524 and 525 can be placed on the outside of the
container by sliding them onto the outside of the container. The
inner sleeve 524 may be attached or sealed in place.
[0085] FIGS. 7 and 8 show jacketed embodiments of pervaporative
containers. As shown in FIG. 7 the cooling jacket may be made of a
detachable sleeve consisting of an outer hydrophobic pervaporative
layer 535 and an inner porous liquid holding or absorbing layer
534. In the embodiment of FIG. 8, the outside jacket 541 is filled
through special ports 543 with water or other volatile fluids 541
and the contents of the inner liquid container 540 are maintained
at a sub-ambient temperature. One advantage to this configuration
lies in that a carbonated beverage can be, stored in this container
without losing carbonation. In addition, a liquid with a low
propensity to pervaporate, such as a liquid high in electrolytes or
sugar can be placed in the inner chamber 540 of the container while
distilled water or other easily pervaporated liquid 541 is placed
in the outside chamber to obtain an adequate temperature drop.
[0086] Another embodiment for a sponge 533 or jacketed 542
pervaporative-configuration as shown in FIGS. 7 and 8 is for the
use of an oleophobic pervaporative matrix that retains organic
liquids such as alcohol. In such a configuration the outside jacket
533, 542 are be filled with ethanol, and serves as the
pervaporative coolant 534, 541.
[0087] FIG. 10 illustrates a pervaporatively-cooled drinking cup
similar in function to FIGS. 1A, 1B, 2, 3A and 3B. Assembly may be
performed wrapping a planar pervaporative matrix around or pushing
the matrix 555 over the cup body 556 as a cylinder and attaching
the material by adhesive, potting, thermal welding or ultrasonic
welding. Insert molding may be used to directly attach the material
into the bottle frame and walls.
[0088] FIGS. 11A, 11B and 11C show a configuration for producing a
cooling container for the storage of beverages and foodstuffs 568.
In this configuration the lid 558, the cooler walls 559 and 564 or
preferably both the lid 572 and the walls 559 and 564 contain a
liquid-filled 860 pervaporative jacket 566 and 578. The container
may further comprise one or more layers of insulation. The
container can be used to store foods and beverages 568 at
sub-ambient temperatures for several days at a time. In one
embodiment, assembly of the cooler body 563 is performed by placing
the planar pervaporative matrix 566 inside the case body 564 and
attaching the material by adhesive, potting, thermal welding or
ultrasonic welding. Alternatively, insert molding is used to
directly attach the material 566 into the frame and walls 564.
[0089] One proposed solution for heat stress relief is based on the
idea of pervaporation. A chilled hydration pack or other cooling
garment utilizing a pervaporative cooling mechanism, such as this
would find applications not only in the military as a personal
cooling system but also for a sports enthusiast who could increase
their endurance by releasing more heat from their bodies during a
race. Using water or a combination of water and ethanol (preferably
about 5 to 15%) as a pervaporative coolant source allows such a
device to be non-hazardous and provide an additional functionality
such as an extra pouch for pervaporatively-chilled drinking water.
Chilled drinking water would also lessen the heat load on an
individual wearing a protective suit or clothing.
[0090] The pervaporative hydration pack described herein will
follow a design similar to the pervaporative beverage cooling
bottles, which were previously designed. A comparison of the
cooling efficiency using pervaporative cooling (2400 J/g) versus
the heat of fusion (335 J/g) plus the warming of the liquid (105
J/g) to room temperature (77.degree. F. reveals that pervaporative
cooling is five times more efficient on a mass basis than using
ice. Tables 1, 2, and 3 provide data to show what happens to the
pervaporative cooling bottles under different conditions of wind
speed and matrix composition at room temperature and a relative
humidity of 30 to 40%.
[0091] FIG. 14 shows one embodiment of a pervaporatively-cooled
drinking pouch 594, shown in an optional webbed strap-on holder
599. In one embodiment, a strap is attached directly to the body
595 and no holder, webbed or otherwise, is used. A pervaporative
pouch such as this can be worn over the shoulder, strapped into a
belt loop or another portion of the body using securing straps 600
or similar attachment devices or attached to the side of an
existing belt. In one embodiment, the webbing 601 is sewn from
nylon netting and the straps 600 are Velcro, a Nylon/Velcro
Composite, or other natural or synthetic material. The various
portions of the pouch porous matrix 595 can be assembled by thermal
sealing, thermal welding, ultrasonic welding, adhesive lamination,
or other methods discussed herein in relation to other containers.
In one embodiment, a pervaporatively cooled drinking tube 602
comprises an outer pervaporative hydrophobic layer 604, which
substantially prevents or reduces liquid leakage and pervaporative
cooling, and an internal liquid wettable layer 605. Once liquid is
introduced through the center 603 of this layered construct 602 the
liquid penetrates into the hydrophilic material producing a liquid
lock 605 which prevents or substantially reduces the amount of air
entering the center of the tube 603 through the porous matrix 604.
The liquid trapped in the hydrophilic matrix 605 is free to
pervaporate through the outer hydrophobic matrix 604. This
combination of hydrophilic 605 and hydrophobic 604 matrices in a
tube format 602 provides the benefit of delivering chilled drinking
water directly from the internal tube volume 603. As noted above,
this tube may be used with a pervaporative or non-pervaporative
pouch, or it may be used with other containers, both pervaporative
and non-pervaporative. One method of manufacture of a pervaporative
tube 602 is to plasma treat the center of a hydrophobic porous PTFE
tube rendering the inner portion of the tube 605 hydrophilic.
[0092] Preferred designs for pervaporative cooling devices are
simple and can be operated under ambient conditions to cool and/or
maintain the coolness of fluid or solid contents of the container
without the weight and portability limitations associated with
mechanical pumping or the need for the application of an external
mechanical vacuum to increase the pervaporative cooling rate. In a
preferred embodiment, the radial dimensions of a container of the
type in FIG. 1A are large enough such that convective mixing by
natural convection of liquid contents is obtained. This is because,
in some cases, the thermal conductivity of the liquid alone may not
be high enough to effectively maintain a generally uniform
temperature distribution throughout the container. When-the liquid
at the inner walls of the container are cooled, this reduces the
density of the liquid at the inner walls as compared to that in the
center. Because of this density difference, the cooler liquid flows
down the inside walls of the container to the bottom of the
container where it is entrained back up into a circulatory pattern
within the middle of the container in a process called natural
convection, as opposed to forced convection. When the cooling rate
is high enough, convective eddies break off from the side of-the
container and enhance thermixing rate.
[0093] These phenomena and their occurrence can be predicted using
a combination of calculated dimensionless parameters, namely the
Grashof Number (parameter for fluid buoyancy in a gravitational
field) and the Prandlt Number (parameter that describes the thermal
and capacitive nature of the liquid). The combination of these two
parameters leads to the calculation of the Nusslet Number (an
overall heat transfer parameter). Natural convection within a
pervaporative container will enhance the cooling efficiency and the
cooling rate of the device by allowing for convective heat transfer
through the buoyant fluid in lieu of thermal conduction through the
same liquid medium.
[0094] Table 1 presents endpoint pervaporative cooling data at a
relative air humidity of 30% to 41% and different ambient air
velocities and the effect of a porous insulative matrix. Tables 2
and 3 present endpoint water pervaporative cooling data at
different relative humidity in the shade (Table 2) or in the
presence of direct solar radiation (Table 3). The pervaporative
materials are PTFE (polytetrafluoroethylene) or sintered UHMWPE
(ultra high molecular weight polyethylene). X-7144, X-6919, and
402HP are all UHMWPE materials of varying porosity, pore size and
thickness as outlined in the tables. TABLE-US-00001 TABLE 1 Pore
Cool @ Cool @ Matrix Porosity Size Thickness Liquid Loss Flux Cool
2 mph 5 mph Material (%) (.mu.m) (mm) (%/hr) (g cm.sup.2/s .times.
10.sup.6 (.degree. F.) (.degree. F.) (.degree. F.) Control 1 None
None 1.5 0 0 0 0 0 PE Control 2 None None 1.5 0 0 0 0 0 PE PVDF 75
0.5 0.1 0.4-3.0 1.9-7.6 12.7 14.3 14.8 UHMWPE 35-50 7 0.6 0.3-1.0
1.2-6.6 10.6 12.6 13.9 PVDF 75 13.5 5.1 0.4-1.9 2.0-6.5 12.1 11.5
10.7 w/foam insulation UHMWPE 35-50 20 5.6 0.3-0.8 2.2-5.2 9.8 10.5
11.3 w/foam insulation
[0095] TABLE-US-00002 TABLE 2 Shade/ Pore Thick- Pervaporative RH
38.6%/75.degree. F. size ness Temp. Cool Matrix Material Porosity
(.mu.m) (mm) (.degree. F.) (.degree. F.) Control #1 (PE) None None
1.5 72.1 -- Control #2 (PE) None None 1.5 71.9 -- X-7744 35 to 50%
7 0.6 63.6 8.4 X-6919 35 to 50% <15 1.6 65.1 6.9 402 HP 40 to
45% 40 0.6 63.4 8.7 402 HP 40 to 45% 40 1.3 64.7 7.3 Supported PTFE
75% >50 0.3 63.4 8.7
[0096] TABLE-US-00003 TABLE 3 Full Sun/RH Pore Thick-
41.0%/77.degree. F.* size ness Temp. Pervaporative Matrix Material
Porosity (.mu.m) (mm) (.degree. F.) Cool (.degree. F.) Control #1
(PE) None None 1.5 93.6 -- Control #2 (PE) None None 1.5 93.3 --
X-7744 35 to 50% 7 0.6 71.3 22.2 X-6919 35 to 50% <15 1.6 73.1
20.4 402 HP 40 to 45% 40 0.6 73.1 20.4 402 HP 40 to 45% 40 1.3 73.7
19.7 Supported PTFE 75% >50 0.3 73.1 20.4
[0097] Table 1 sets forth endpoint water pervaporative cooling data
at different ambient air velocities and the effect of a 1/16 inch
open-cell porous urethane insulative matrix at a relative humidity
of 30%. Tables 2 and 3 set forth endpoint water pervaporative
cooling data at different relative humidity and in the dark or in
the presence of direct solar irradiation. The pervaporative
materials in all three tables are PTFE or sintered UHMWPE (ultra
high molecular weight polyethylene).
[0098] Additional enhancement in cooling efficiency may be seen
with the container as the outside relative humidity drops and if
the container is placed in direct sunlight. The lower external
humidity increases the vapor concentration gradient, and the
externally applied heat raises the liquid temperature and vapor
pressure, which lead to a rise in the pervaporative flux. Depending
on ambient conditions, the geometry and materials selection of the
container, this process can maintain a sub-ambient cool in the
container of 22* below ambient temperature (see Table 3). The time
to attain this cooled temperature for a liquid volume of 700 ml is
about 2 hours as demonstrated in FIG. 9 for a variety of
pervaporative matrices and combinations thereof.
[0099] One preferred embodiment of evaporative cooling container
includes a single or combined porous matrix having a pervaporative
layer thickness of about 0.025 mm (0.001 in.) to 10 mm (0.394 in.).
Additionally, to increase the efficiency of the pervaporative
process, the matrix preferably has qualities such that render it
minimally thermally conducting. It is preferable that the matrix
does not substantially impede vapor diffusion, such that, in one
embodiment, a pore size above about 100 nm is preferred. Preferred
surface porosities of the matrix are between about 15 and 90%
including about 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80,
and 85%. A porous matrix with a low thermal conductivity, such as a
porous perfluorinated Styrofoam, an expanded porous matrix, or an
open cell porous matrix made from hollow fused particles, can help
to substantially prevent or reduce undue heat transfer from the
surroundings in to the container.
[0100] The various methods and techniques described above provide
some of the numerous ways to carry out the invention. Of course, it
is to be understood that not necessarily all objectives or
advantages described may be achieved in accordance with any
particular embodiment described herein or with any other single
embodiment. Thus, for example, those skilled in the art will
recognize that the methods m ay be performed and/or t he articles
made in a manner that achieves or optimizes one advantage or group
of advantages as taught herein without necessarily achieving other
objectives or advantages as may be taught or suggested herein.
[0101] Furthermore, the skilled artisan will recognize the
interchangeability of various features from different embodiments.
Similarly, the various features and steps discussed above, as well
as other known equivalents for each such feature or step, can be
mixed and matched by one of ordinary skill in this art to perform
methods in accordance with principles described herein.
[0102] Although the invention has been disclosed in the context of
certain embodiments and examples, it will be understood by those
skilled in the art that the invention extends beyond the
specifically disclosed embodiments to other alternative embodiments
and/or uses and obvious modifications and equivalents thereof.
* * * * *