U.S. patent application number 13/207607 was filed with the patent office on 2012-02-16 for articles and devices for thermal energy storage and methods thereof.
This patent application is currently assigned to DOW GLOBAL TECHNOLOGIES LLC.. Invention is credited to David H. Bank, Kalyan Sehanobish, Andrey N. Soukhojak, Jay M. Tudor, Parvinder S. Walia.
Application Number | 20120037148 13/207607 |
Document ID | / |
Family ID | 44511590 |
Filed Date | 2012-02-16 |
United States Patent
Application |
20120037148 |
Kind Code |
A1 |
Tudor; Jay M. ; et
al. |
February 16, 2012 |
ARTICLES AND DEVICES FOR THERMAL ENERGY STORAGE AND METHODS
THEREOF
Abstract
The present invention relates to articles and heat storage
devices for storage of thermal energy. The articles include a metal
base sheet and a metal cover sheet, wherein the metal base sheet
and the metal cover sheet are sealingly joined to form one or more
sealed spaces. The articles include a thermal energy storage
material that is contained within the sealed spaces. The sealed
spaces preferably are substantially free of water or includes
liquid water at a concentration of about 1 percent by volume or
less at a temperature of about 25.degree. C., based on the total
volume of the sealed spaces. The articles include one or more of
the following features: a) the pressure in a sealed space is about
700 Torr or less, when the temperature of the thermal energy
storage material is about 25.degree. C.; b) the metal cover sheet
includes one or more stiffening features, wherein the stiffening
features include indents into the sealed space, protrusions out of
the sealed space, or both, that are sufficient in size and number
to reduce the maximum von Mises stress in the cover sheet during
thermal cycling; c) the metal cover sheet and/or the metal base
sheet includes one or more volume expansion features; or d) the
metal cover sheet has a thickness, t.sub.c, and the metal base
sheet has a thickness, t.sub.b, wherein t.sub.c is greater than
t.sub.b; so that the article is durable. For example, the article
does not leak after thermal cycling between about 25.degree. C. and
about 240.degree. C., for 1,000 cycles.
Inventors: |
Tudor; Jay M.; (Goodrich,
MI) ; Soukhojak; Andrey N.; (Midland, MI) ;
Bank; David H.; (Midland, MI) ; Sehanobish;
Kalyan; (Rochester Hills, MI) ; Walia; Parvinder
S.; (Midland, MI) |
Assignee: |
DOW GLOBAL TECHNOLOGIES
LLC.
Midland
MI
|
Family ID: |
44511590 |
Appl. No.: |
13/207607 |
Filed: |
August 11, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61373008 |
Aug 12, 2010 |
|
|
|
Current U.S.
Class: |
126/400 ; 53/432;
53/467; 53/473 |
Current CPC
Class: |
Y02E 60/145 20130101;
Y02E 60/14 20130101; F28F 2275/06 20130101; F28F 2225/00 20130101;
F28F 2265/14 20130101; F28D 20/02 20130101; F28D 2020/0008
20130101 |
Class at
Publication: |
126/400 ; 53/473;
53/432; 53/467 |
International
Class: |
F24H 7/00 20060101
F24H007/00; B65B 1/04 20060101 B65B001/04; B65B 31/02 20060101
B65B031/02 |
Claims
1. An article comprising: a metal base sheet; a metal cover sheet,
wherein the metal base sheet and the metal cover sheet are
sealingly joined to form one or more sealed spaces; a thermal
energy storage material, wherein the thermal energy storage
material is contained within the sealed spaces; wherein the sealed
spaces are substantially free of water or includes liquid water at
a concentration of about 1 percent by volume or less at a
temperature of about 25.degree. C., based on the total volume of
the sealed spaces; and wherein the article includes one or more of
the following features: a. the pressure in a sealed space is about
700 Torr or less, when the temperature of the thermal energy
storage material is about 25.degree. C.; b. the metal cover sheet
includes one or more stiffening features, wherein the stiffening
features include indents into the sealed space, protrusions out of
the sealed space, or both, that are sufficient in size and number
to reduce the maximum von Mises stress in the cover sheet during
thermal cycling; c. the metal cover sheet and/or the metal base
sheet includes one or more volume expansion features; or d. the
metal cover sheet has a thickness, t.sub.c, and the metal base
sheet has a thickness, t.sub.b, wherein t.sub.c is greater than
t.sub.b; so that the article does not leak after thermal cycling
between about 25.degree. C. and about 240.degree. C., for 1,000
cycles.
2. The article of claim 1, wherein the pressure in a sealed space
is a vacuum of about 600 Torr or less, at a temperature of about
25.degree. C.
3. The article of claim 2, wherein the article is prepared by a
process including a step of joining the metal base sheet and the
metal cover sheet when the thermal energy storage material is at a
joining temperature (T.sub.j) of at least the liquidus temperature
of the thermal energy storage material (T.sub.L, TESM).
4. The article of claim 1, wherein i) the ratio of the thickness of
the metal cover sheet to the thickness of the metal base sheet,
t.sub.c/t.sub.b, is about 1.05 or more; ii) the difference between
the thickness of the metal cover sheet and the thickness of the
metal base sheet, t.sub.c-t.sub.b, is about 0.02 mm or more; or
iii) both i) and ii).
5. The article of claim 1, wherein the article includes one or more
welds joining the metal cover sheet and the metal base sheet,
wherein the one or more welds completely encloses the sealed
spaces; the article has an opening near the center of the article
so that a heat transfer fluid can flow through the opening; and the
article is sealed around a periphery of the opening, so that the
heat transfer fluid does not contact the thermal energy storage
material in the sealed space.
6. The article of claim 1, wherein the metal cover sheet includes
one or more stiffening features.
7. The article of claim 1, wherein the metal cover sheet, the metal
base sheet, or both includes one or more volume expansion
features.
8. The article of claim 7 wherein the one or more volume expansion
features includes dimples, chevrons, wrinkles, folds, convolutions,
or any combination thereof.
9. The article of claim 1, wherein the metal cover sheet is
embossed so that the Von Mises stress of the article at a
temperature of about 250.degree. C. is reduced by about 10% or more
compared with an article in which the metal cover sheet is
generally flat.
10. The article of claim 1, wherein the Von Mises stress in both
the metal base sheet and the metal cover sheet due to the thermal
expansion of the thermal energy storage material during repeated
thermal cycling between about 30.degree. C. and about 250.degree.
C. is less than the yield stress of the metal of the cover
sheet.
11. The article of claim 1, wherein the sealed spaces of the
article do not leak after being heated to about 400.degree. C. for
about 4 hours.
12. The article of claim 1, wherein the thermal energy storage
material has a liquidus temperature of about 25.degree. C. or
more.
13. The article of claim 12, wherein the thermal energy storage
material has a liquidus temperature of about 150.degree. C. or
more; and the thermal energy storage material is substantially
anhydrous.
14. A process for forming an article of claim 1, wherein the metal
base sheet includes one or more troughs capable of containing a
liquid, and the process comprises a step of at least partially
filling one or more troughs with the thermal energy storage
material.
15. The process of claim 14, wherein the thermal energy storage
material is at a predetermined temperature that is at least the
liquidus temperature of the thermal energy storage material when
the base sheet and the cover sheet are sealingly joined, so that
upon cooling the article to about 25.degree. C. a vacuum is formed
in the sealed space.
16. A process of claim 14, wherein the step of sealingly joining
the base sheet and the cover sheet is started prior to the step of
filling the trough with the thermal energy storage material and is
finished after the step of filling the trough with the thermal
energy storage material.
17. The process of claim 14, wherein the article is prepared by a
process including a step of joining the metal base sheet and the
metal cover sheet to form the sealed space, wherein the step of
joining includes a step of applying a vacuum to the region of the
sealed space prior to joining the sheets.
18. A device including a stack of two or more articles of claim
1.
19. The device of claim 18, wherein each articles each include an
opening and wherein the articles are arranged so that openings are
generally aligned in an axial direction, and the stack of articles
is contained in an insulated container.
20. A process for storing heat comprising a step of: transferring a
sufficient amount of thermal energy to the article of claim 1, so
that the thermal energy storage material in the article is heated
to a temperature of about 200.degree. C. or more.
Description
CLAIM OF BENEFIT OF FILING DATE
[0001] The present invention claims the benefit of the filing date
of U.S. Provisional Patent Application No. 61/373,008, filed on
Aug. 12, 2010, the contents of which are hereby incorporated by
reference in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to thermal energy storage
using a thermal energy storage material and to the packaging of the
thermal energy storage material to allow for both efficient heat
storage and efficient heat transfer.
BACKGROUND OF THE INVENTION
[0003] Industry in general has been actively seeking a novel
approach to capture and store waste heat efficiently such that it
can be utilized at a more opportune time. Further, the desire to
achieve .energy storage in a compact space demands the development
of novel materials that are capable of storing high energy content
per unit weight and unit volume. Areas of potential application of
breakthrough technology include transportation, solar energy,
industrial manufacturing processes as well as municipal and/or
commercial building heating.
[0004] Regarding the transportation industry, it is well known that
internal combustion engines operate inefficiently. Sources of this
inefficiency include heat lost via exhaust, cooling, radiant heat
and mechanical losses from the system. It is estimated that more
than 30% of the fuel energy supplied to an internal combustion
engine (internal combustion engine) is lost to the environment via
engine exhaust.
[0005] It is well known that during a "cold start" internal
combustion engines operate at substantially lower efficiency,
generate more emissions, or both, because combustion is occurring
at a non-optimum temperature and the internal combustion engine
needs to perform extra work against friction due to high viscosity
of cold lubricant. This problem is even more important for hybrid
electric vehicles in which the internal combustion engine operates
intermittently thereby prolonging the cold start conditions, and/or
causing a plurality of occurrences of cold start conditions during
a single period of operating the vehicle. To help solve this
problem, original equipment manufacturers are looking for a
solution capable of efficient storage and release of waste heat.
The basic idea is to recover and store waste heat during normal
vehicle operation followed by controlled release of this heat at a
later time thereby reducing or minimizing the duration and
frequency of the cold start condition and ultimately improving
internal combustion engine efficiency, reducing emissions, or
both.
[0006] To be a practical solution, the energy density and the
thermal power density requirements for a thermal energy storage
system are extremely high. Applicants have previously filed 1) U.S.
Patent Application Publication No. 2009-0211726 by Soukhojak et
al., entitled "Thermal Energy Storage Materials" and published on
Aug. 27, 2009; 2) U.S. Patent Application Publication No.
2009-0250189 by Bank et al., entitled "Heat Storage Devices" and
published on Oct. 8, 2009, 3) PCT Application No. PCT/US09/67823
entitled "Heat Transfer Systems Utilizing Thermal Energy Storage
Materials" and filed on Dec. 14, 2009, and 4) U.S. Provisional
Application No. 61/299,565 entitled "Thermal Energy Storage" and
filed on Jan. 29, 2010. These previous applications are
incorporated herein by reference in their entirety.
[0007] There are known heat storage devices and exhaust heat
recovery devices in the prior art. However, in order to provide a
long term (e.g., greater than about 6 hour) heat storage
capability, they generally occupy a large volume, require pumping
of a large volume of heat transfer fluid, require a relatively
large pump to overcome the hydraulic resistance, and the like.
Therefore, there is a need for a heat storage system which can
offer an unprecedented combination of high energy density, high
power density, long heat retention time, light weight, low
hydraulic resistance for heat transfer fluid flow, or any
combination thereof.
[0008] The issue of packaging of the thermal energy storage
materials for applications requiring systems that are light weight,
such as in transportation, requires both strong packaging and
packaging that is light weight. For example, the packaging should
be durable so that it may contain a large concentration of thermal
energy storage material, contain the thermal energy storage
material over a wide range of temperatures (upon which it may
undergo large changes in volume), contain the thermal energy
storage material in a plurality of cells or capsules that are
sealed from each other, or any combination thereof. The need for
light weight thermal energy storage systems may require that the
weight of the packaging be reduced.
[0009] For example, there is a need for thermal energy storage
material that is encapsulated in capsules that are light weight,
have a high energy density, or have a high power density; and are
durable (e.g., so that the capsules do not leak upon heating to a
temperature of about 400.degree. C.; the capsules do not leak upon
repeated heating between a temperature of about 25.degree. C. and a
temperature of about 240.degree. C. for about 1,000 cycles or more;
or both).
SUMMARY OF THE INVENTION
[0010] One aspect of the invention is an article comprising: a base
sheet (preferably a metal base sheet); a cover sheet (preferably, a
metal cover sheet) sealingly joined to the base sheet to form a
capsular structure, wherein the capsular structure includes one,
two or more sealed spaces; a thermal energy storage material,
wherein the thermal energy storage material is contained within the
sealed spaces, and wherein the thermal energy storage material has
a liquidus temperature of about 150.degree. C. or more; wherein the
sealed spaces are substantially free of water or includes liquid
water at a concentration of about 1 percent by volume or less at a
temperature of about 25.degree. C., based on the total volume of
the sealed spaces; and wherein the article includes one or more of
the following features: a) the pressure in a sealed space is a
vacuum of about 700 Torr or less, when the temperature of the
thermal energy storage material is about 25.degree. C.; b) the
cover sheet includes one or more one or more stiffening features,
wherein the stiffening features include indents into the sealed
space, protrusions out of the sealed space, or both, that are
sufficient in size and number to reduce the maximum von Mises
stress in the cover sheet during thermal cycling; c) the base sheet
and/or the cover sheet includes one or more volume expansion
features; or d) the cover sheet has a thickness, t.sub.c, and the
base sheet has a thickness, t.sub.b, wherein t.sub.c is greater
than t.sub.b; so that the article does not leak after thermal
cycling between about 25.degree. C. and about 240.degree. C., for
about 1,000 cycles. The stiffening feature may be any feature (such
as an indention or a protrusion) that redistributes the stresses in
the base sheet and the cover sheet so that when the pressure in the
sealed space increases (e.g., due to thermal expansion, or melting
of the thermal energy storage material) the maximum von Mises
stress is reduced compared to a base sheet and/or a cover sheet
without the stiffening feature and subjected to the same pressure.
Without limitation, examples of stiffening features that may be
employed in the metal cover sheet include dimples, chevrons, ribs,
or any combination thereof.
[0011] In a particularly preferred aspect of the invention, the
capsular structure has one or more fluid passages which are
sufficiently large to allow a heat transfer fluid to flow through
the one or more fluid passages; and when the capsular structure is
in contact with a heat transfer fluid, the thermal energy storage
material is isolated from the heat transfer fluid.
[0012] Another aspect of the invention is a device including a
container and a stack of two or more articles within the container.
For example, the device may contain a plurality of articles
described herein. Preferably, each article includes a fluid passage
and contains the thermal energy storage material. Preferably the
articles having a fluid passage are stacked so that their fluid
passages are generally aligned, preferably axially.
[0013] Another aspect of the invention is a process for preparing
an article, such as an article described herein, including the
steps of: forming one, two or more troughs in a base sheet; ii) at
least partially filling one, two or more of the troughs with a
thermal energy storage material; and at least partially joining
(e.g., sealingly joining) a first metal foil (e.g., the base sheet)
with a second metal foil (e.g., the cover sheet) to form a sealed
space; wherein the thermal energy storage material includes a metal
salt, and wherein the metal salt is in a molten state during the
joining step.
[0014] Yet another aspect of the invention is directed at a process
for storing heat comprising a step of: transferring a sufficient
amount of thermal energy to an the article of the invention, so
that the thermal energy storage material in the article is heated
to a temperature of about 200.degree. C. or more.
[0015] The articles, devices, systems and processes of the present
invention advantageously are capable of containing a high
concentration of thermal energy storage material so that a large
amount of thermal energy can be stored (e.g., having a high energy
density), are capable of having a high surface area between the
heat transfer fluid and the article containing the thermal energy
storage material so that heat can be quickly transferred into
and/or out of the thermal energy storage material (e.g., having a
high power density, preferably greater than about 8 kW/L), are
capable of having multiple flow paths that have similar or equal
hydraulic resistance so that heat is uniformly transferred to
and/or transferred from different regions; have a rotational
symmetry so that they may be arranged easily; have a structure that
is strong and durable; have a high heat storage density so that
they can be used in applications requiring compact designs, light
weight components, or both; have lower hydraulic resistance for a
heat transfer fluid flow (for example, a pressure drop of less than
about 1.5 kPa at a heat transfer fluid pumping rate of about 10
liters/min) so that the pumping requirements for the heat transfer
fluid are reduced, are sufficiently strong so that the thermal
energy storage material does not leak from a sealed space after
heating a capsular structure including the thermal energy storage
material to a temperature of about 400.degree. C., are sufficiently
durable so that the thermal energy storage material does not leak
from a sealed space after repeatedly heating the capsular structure
with the thermal energy storage material between about 25.degree.
C. and about 240.degree. C. for about 1,000 cycles or more, or an
combination thereof.
BRIEF DESCRIPTION OF THE FIGURES
[0016] The present invention is further described in the detailed
description which follows, in reference to the noted plurality of
drawings by way of non-limiting examples of embodiments of the
present invention, in which like reference numerals represent
similar parts throughout the several views of the drawings, and
wherein:
[0017] FIG. 1 is a drawing of an illustrative article having a
sealed compartment.
[0018] FIG. 2A is a cross-sectional view of an illustrative article
including a plurality of sealed spaces.
[0019] FIG. 2B is a drawing of an illustrative cross-section of a
single capsule having a sealed space that may be employed in the
article.
[0020] FIG. 3 is a drawing of an illustrative base sheet that may
be employed in the article.
[0021] FIG. 4A is a drawing of an illustrative cover sheet having
chevrons that may be employed in the article.
[0022] FIG. 4B is a drawing of an illustrative capsule including a
cover sheet having dimples that may be employed in an article
having one or more capsules.
[0023] FIG. 4C is a drawing of a section of an illustrative cover
sheet including dimples that may be employed in the article.
[0024] FIG. 4D is a drawing of an illustrative cover sheet having a
plurality of stiffening features, such as plurality of protrusions
and/or recesses that may be used in an article.
[0025] FIG. 5A is a drawing of an illustrative cross-section of a
sealed compartment at the temperature at which the compartment is
sealed.
[0026] FIG. 5B is a drawing of an illustrative cross-section of a
sealed at a temperature below the sealing temperature.
[0027] FIG. 5C is a drawing of an illustrative cross-section of a
sealed compartment at a temperature above the sealing
temperature.
[0028] FIGS. 6A, 6B, and 6C are drawings of an illustrative sheet
that has been formed to have ribs.
[0029] FIGS. 7A and 7B are drawings illustrating a sheet having a
volume expansion feature that allows the volume of the sealed space
to increase (e.g., to accommodated the volume expansion of the
thermal energy material as it is heated and/or melts).
[0030] FIG. 8 is an illustrative graph showing the relationship
between the thickness of the cover sheet and the maximum von Mises
stress in the cover sheet when the cover sheet is employed in an
article containing a thermal energy storage material and the
thermal energy storage material is heated.
[0031] FIG. 9 is an illustrative graph showing the relationship
between the thickness of the cover sheet and the maximum expected
von Mises stress in the cover sheet for a cover sheet that is flat
and for a cover sheet that includes ribs.
[0032] FIG. 10 is an illustrative graph showing the relationship
between the thickness of the cover sheet and the maximum expected
von Mises stress in the cover sheet for a cover sheet that is flat,
for a cover sheet that includes dimples, for a cover sheet that
includes chevrons, and for a cover sheet that includes ribs.
[0033] FIG. 11 is an illustrative drawing of a portion of tooling
that may be employed in manufacturing a sheet that includes
ribs.
[0034] FIG. 12 shows an illustrative stack of articles.
[0035] FIG. 13 shows a surface of a base sheet of an article
including one or more sealed compartment. FIG. 13 illustrates that
a sealed compartment may have a primary seal and one or more
secondary seals.
[0036] FIG. 14 is a drawing of an illustrative heat storage
device.
[0037] FIG. 15. Is a drawing of an illustrative tooling for
embossing a base sheet.
[0038] FIG. 16 shows a surface of a base sheet of an article
including one or more spaces being filled with thermal energy
storage material using a nozzle.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0039] In the following detailed description, the specific
embodiments of the present invention are described in connection
with its preferred embodiments. However, to the extent that the
following description is specific to a particular embodiment or a
particular use of the present techniques, it is intended to be
illustrative only and merely provides a concise description of the
exemplary embodiments. Accordingly, the invention is not limited to
the specific embodiments described below, but rather; the invention
includes all alternatives, modifications, and equivalents falling
within the true scope of the appended claims.
[0040] As will be seen from the teachings herein, the present
invention provides unique articles, devices, systems, and process
for storing thermal energy and/or transferring stored thermal
energy to a fluid. For example, the articles and devices for
storing thermal energy of the present invention are more efficient
at storing thermal energy, allow for transferring thermal energy
more uniformly, allow for transferring thermal energy with a
smaller pressure drop of the heat transfer fluid, or any
combination thereof.
[0041] Various aspects of the invention are predicated on an
article including a capsular structure having one or more sealed
spaces (i.e., capsules) and one or more thermal energy storage
materials that are encapsulated in the one or more sealed spaces of
the capsular structure so that the thermal energy storage material
cannot flow out of the capsular structure or otherwise be removed
from the capsular structure. When the thermal energy storage
material is heated during operation, the volume may increase due to
thermal expansion, due to difference in the densities of the liquid
and solid phases of the thermal energy storage material, or both.
The increase in volume of the thermal energy storage material may
be about 5% or more, about 10% or more, about 15% or more, or even
about 20% or more. For example, a metal salt, such as lithium
nitrate, may increase in volume by more than 20% when heated from
about 23.degree. C. to about 300.degree. C. It will be appreciated
that as the thermal energy storage material is heated, the pressure
in the sealed space may increase. The capsular structure should be
sufficiently durable so that it does not leak or otherwise fail
when the thermal energy storage material expands during use. The
capsular structure preferably has a geometry that allows a heat
transfer fluid to efficiently remove heat from the thermal energy
storage material. Without limitation, examples, of preferred
capsular structures include those described in U.S. Patent
Application Publication No. 2009/0250189 by Soukhojak et al.,
published on Oct. 8, 2009, and U.S. Provisional Patent Application
No. 61/299,565 filed on Jan. 29, 2010, incorporated herein by
reference. For example, the capsular structure may have a geometry
that includes one or more fluid passages that are sufficiently
large so that the capsular structure is capable of allowing a fluid
(e.g., a heat transfer fluid) to flow through the fluid passage.
The thermal energy storage materials may be sufficiently
encapsulated in one or more of the sealed spaces so that when the
heat transfer fluid contacts the capsular structure, the thermal
energy storage material is isolated from the fluid.
[0042] A variety of approaches have been identified that
advantageously improve the durability of the capsular structure
including having a pressure in a sealed space that is a vacuum of
about 700 Torr or less when the temperature of the thermal energy
storage material is about 25.degree. C., using a metal base sheet
that includes one or more stiffening features (e.g., one or more
ribs), using a metal cover sheet that includes one or more
stiffening features (e.g., one or more ribs, one or more dimples,
one or more chevrons, or any combination thereof), using a cover
sheet having a thickness greater than the thickness of the base
sheet, or any combination thereof.
[0043] By reducing the pressure of a sealed space at a temperature
of about 25.degree. C., the pressure of the sealed space when the
thermal energy storage material is heated may also be reduced. The
pressure of a sealed space at a temperature of about 25.degree. C.
may be reduced to about 700 Torr or less using any convenient
means. By way of example, the cover sheet and the base sheet may be
joined to formed the sealed space when the thermal energy storage
material is at a joining temperature, T.sub.j, that is sufficiently
high so that when the thermal energy storage material in the sealed
space is cooled, the thermal energy storage material contracts and
the pressure in the sealed space drops below about 700 Torr. The
joining temperature may be greater than the liquidus temperature,
T.sub.L, TESM, of the thermal energy storage material. Preferably
the joining temperature, T.sub.j, is about T.sub.L, TESM+10.degree.
C. or more, even more preferably about T.sub.L, TESM+20.degree. C.
or more, even more preferably about T.sub.L, TESM+30.degree. C. or
more, even more preferably about T.sub.L, TESM+40.degree. C. or
more, even more preferably about T.sub.L, TESM+50.degree. C. or
more, and most preferably about T.sub.L, TESM+60.degree. C. or
more. By way of example, T.sub.j, may be about 200.degree. C. or
more, preferably about 230.degree. C. or more, more preferably
about 250.degree. C. or more, even more preferably about
270.degree. C. or more, and most preferably about 290.degree. C. or
more. The temperature of the thermal energy storage when the base
sheet and the cover sheet are joined may be about 700.degree. C. or
less, preferably about 500.degree. C. or less, and more preferably
about 400.degree. C. or less.
[0044] In another example, the cover sheet and the base sheet may
be joined while a vacuum is applied to the region that becomes the
sealed space. If employed, the vacuum should have a pressure
sufficiently low so that upon sealingly joining the base sheet and
the cover sheet, the sealed space is a vacuum. For example, a
vacuum may be applied having a pressure of about 700 Torr or less,
about 660 Torr or less, about 600 Torr or less, about 550 Torr or
less, about 500 Torr or less, about 400 Torr or less, or about 300
Torr or less. As such, the entire joining process may be done in a
vacuum environment. The cover sheet and the base sheet may be
joined while the pressure in the region that becomes the sealed
space is about 0.1 Torr or more, preferably about 1.0 Torr or more,
and more preferably about 10 Torr or more. Lower pressures may also
be employed. Preferably the thermal energy storage material is at a
predetermined sealing temperature that is at an elevated
temperature when the base sheet and the cover sheet are sealingly
joined, so that upon cooling the article to about 25.degree. C. a
vacuum is formed in the sealed space. The predetermined sealing
temperature may be any temperature at which the density of the
thermal energy storage material is lower than its density at
25.degree. C. Preferably the predetermined sealing temperature is
greater than the liquidus temperature of the thermal energy storage
material (e.g., greater than the liquidus temperature by about
10.degree. C. or more, by about 30.degree. C. or more, or about
60.degree. C. or more). The predetermined sealing temperature may
be about 50.degree. C. or more, about 100.degree. C. or more, about
150.degree. C. or more, about 200.degree. C. or more, about
250.degree. C. or more, or about 300.degree. C. or more. The
predetermined sealing temperature preferably is sufficiently low so
that the thermal energy storage material does not degrade during
the sealing process. The predetermined sealing temperature may be
about 500.degree. C. or less, about 400.degree. C. or less, or
about 350.degree. C. or less.
[0045] When the thermal energy storage material in the sealed space
is at a temperature of about 25.degree. C., the sealed space
preferably is a vacuum of about 600 Torr or less, more preferably
about 500 Torr or less, even more preferably about 400 Torr or
less, and most preferably about 300 Torr or less. The lower limit
on the pressure in the sealed space when the thermal energy storage
material is at 25.degree. C. is based on manufacturability and is
preferably about 0.1 Torr or more, more preferably about 1 Torr and
most preferably about 10 Torr or more.
[0046] The durability of the capsular structure may be increased by
adding one or more stiffening features to the base sheet, the cover
sheet, or both. The stiffening feature may be any feature that
redistributes the stresses in the base sheet and the cover sheet so
that when the pressure in the sealed space increases (e.g., due to
thermal expansion, or melting of the thermal energy storage
material) the maximum von Mises stress is reduced compared to a
base sheet and/or cover sheet without the stiffening feature and
subjected to the same pressure. The stiffening features may be an
indention or protrusion formed in a sheet. As such, the stiffening
feature may be a change in the profile of the sheet. The stiffening
feature may function by redistributing the stresses in a sealed
space (e.g., the stresses obtained when heating the sealed space)
so that the maximum von Mises stress is reduced. A stiffening
feature may be described by its depth (i.e., the amount of change
in the profile, such as compared to the region away from the
stiffening feature), its length, its width, or any combination
thereof. The stiffening feature preferably has a depth of about 0.1
mm or more, more preferably about 0.2 mm or more, even more
preferably about 0.3 mm or more, even more preferably about 0.4 mm
or more, even more preferably about 0.5 mm or more, and most
preferably about 0.6 mm or more. The stiffening feature preferably
has a sufficiently small depth so that the effect of packing or
stacking multiple capsular structures, as described herein, is not
greatly affected. As such, the stiffening feature preferably has a
depth of about 10 mm or less, more preferably about 5 mm or less,
even more preferably about 3 mm or less, and most preferably about
2 mm or less. Without limitation, examples of stiffening features
that may be employed include ribs, dimples, chevrons, and the like.
The stiffening features may include a protrusion or indention that
has a length to width that is greater than about 1, preferably
about 2 or more, even more preferably about 4 or more, and most
preferably about 10 or more, such as a rib. If employed, two ribs
in a base sheet or cover sheet in the region of a sealed space may
be parallel, perpendicular, or at an acute angle. The stiffening
feature may have a generally circular cross-section, such as a
dimple. The stiffening features may be arranged in a repeating
pattern that includes a plurality of stiffening features aligned in
one direction and a plurality of stiffening features aligned in a
different direction, such as a chevron pattern. The stiffening
features are preferably located on the regions of the sheet that
contain a sealed space. There may also be stiffening features
located in the region of a sheet that does not containing a sealed
space.
[0047] The stiffening features (e.g., the stiffening features in a
cover sheet) may have a sufficient size and number so that the
maximum von Mises stress of the capsular structure containing the
thermal energy storage material and heated to 250.degree. C. is
lower than the von Mises stress of an identical capsular structure,
with the exception that the stiffening feature is eliminated (e.g.,
a sheet having a generally smooth surface, is generally flat, or
both, such as a generally flat, smooth cover sheet). The stiffening
features are preferably present in a sufficient size and number so
that the von Mises stress in the capsular structure containing the
thermal energy storage material at 250.degree. C. is reduced by
about 5% or more, more preferably about 10% or more, even more
preferably about 15% or more, even more preferably about 20% or
more, even more preferably about 30% or more, and most preferably
about 40% or more, compared with the von Mises stress of an
identical capsular structure, with the exception that the
stiffening feature are removed (e.g., the sheet has a generally
smooth surface, is generally flat, or both).
[0048] The stiffening feature (optionally along with one or more
other features disclosed herein) may be used to reduce the maximum
von Mises stress in a sealed space containing thermal energy
storage material so that the at a temperature of 250.degree. C.,
the ratio of the maximum von Mises stress in the base sheet and the
cover sheet, S.sub.Max, 250, to the yield stress of the metal at
250.degree. C. (e.g., the metal of the cover sheet, or the lower of
the base sheet and the cover sheet), S.sub.Y, 250, is preferably
about 0.95 or less, more preferably about 0.90 or less, even more
preferably about 0.85 or less, even more preferably about 0.80 or
less, and most preferably about 0.70 or less.
[0049] The durability of the capsular structure may be increased by
adding one or more ribs to the base sheet, the cover sheet or both.
Preferably the base sheet, the cover sheet include a rib structure
(e.g., a sufficient number or ribs and/or ribs of sufficient size)
that provides a sufficient rigidity to the capsular structure so
that the capsular structure does not bend enough to yield and does
not otherwise distort enough to yield.
[0050] It will be appreciated according to the teachings herein
that the base sheet may have a structure, such as a structure
including one or more troughs, that is generally more rigid than
the cover sheet. Advantageously, the thickness of the base sheet
may be sufficiently reduced so that the rigidity of the base sheet
more closely matches the rigidity of the cover sheet. By reducing
the thickness of the base sheet, the volume of the base sheet
and/or the packaging material may be reduced, the weight of the
base sheet and/or packaging material may be reduced, or both. Thus,
a higher percentage of the weight of the capsular structure may be
the weight of the thermal energy storage material. As such, the
base sheet may have a thickness (e.g., an average thickness) of
t.sub.b, and the cover sheet may have a thickness (e.g., an average
thickness) of about t.sub.c, where t.sub.c is greater than t.sub.b.
The ratio of t.sub.c/t.sub.b preferably is about 1.05 or more, more
preferably about 1.10 or more, even more preferably about 1.15 or
more, even more preferably about 1.20 or more, even more preferably
about 1.25 or more, even more preferably about 1.30 or more and
most preferably about 1.35 or more. The difference between t.sub.c
and t.sub.b preferably is about 0.01 mm or more, more preferably
about 0.02 mm or more, even more preferably about 0.03 mm or more,
even more preferably about 0.035 mm or more, even more preferably
about 0.04 mm or more, and most preferably about 0.05 mm or more.
The difference between t.sub.c and t.sub.b preferably is about 1 mm
or less, more preferably about 0.5 mm or less, and most preferably
about 0.25 mm or less. By way of example, i) the ratio of
t.sub.c/t.sub.b may be about 1.05 or more, about 1.10 or more,
about 1.20 or more, or about 1.30 or more; ii) the difference
between t.sub.c/t.sub.b may be about 0.01 mm or more, about 0.02 mm
or more, about 0.03 mm or more, or about 0.05 mm or more; or both
(i) and (ii).
[0051] The base sheet, the cover sheet or both may have one or more
volume expansion features so that the volume of the sealed space
may reversibly increase as the thermal energy storage material
expands during heating and/or melting. Examples of volume expansion
features include wrinkles, pleats, convolutions, folds,
oscillations, and the like. By way of example, the volume expansion
feature may include one, two, or more convolutions, folds, or
pleats. Preferable volume expansion feature may have a generally
bellow, or accordion shape (albeit, typically without an orifice).
A stiffening feature, such as one or more dimples, one or more
chevrons, or one or more ribs, may also function as a volume
expansion feature. It will be appreciated that the size, shape of a
volume expansion feature and number of volume expansion features
will affect the amount by which the volume of the sealed space is
capable of expanding. If employed, the volume expansion features
may be sufficient to increase the volume of the sealed space by
about 5% or more, preferably by about 10% or more, more preferably
by about 13% or more, and most preferably by about 15% or more. The
volume expansion feature may allow the sealed space to sufficiently
expand so that the internal pressure in the sealed space changes
increases by about 35 kPa or less (preferably by about 20 kPa or
less, and more preferably by about 10 kPa or less) when the thermal
energy storage material is heated from about 25.degree. C. to a
temperature at which the thermal energy storage material is a
liquid (e.g., to about 200.degree. C., to about 240.degree. C., or
to about 250.degree. C.).
[0052] Other aspects of the invention include novel arrangements
including a plurality of the articles, novel devices including one
or more of the articles, novel processes for manufacturing the
article, and novel processes for using one or more of the articles.
By employing the novel article, it is possible to assemble devices
capable of storing a large quantity of thermal energy, capable of
rapidly transferring thermal energy into or out of the thermal
energy storage material, capable of being compact, capable of being
light weight, capable of having a low pressure drop of a heat
transfer fluid, or any combination thereof.
[0053] The capsular structure generally has a dimension in one
direction (i.e., a thickness) that is smaller than the dimensions
in the other directions. Without limitation, examples of capsular
structures include those disclosed in U.S. patent application Ser.
No. 12/389,598 entitled "Heat Storage Devices" and filed on Feb.
20, 2009, and U.S. Provisional Application No. 61/299,565 entitled
"Thermal Energy Storage" and filed on Jan. 29, 2010, both
incorporated herein by reference.
[0054] The shape of the capsular structure and/or article may be
defined by the packaging space and may be oddly shaped. The article
may include a cover sheet (i.e., a cover sheet) having a top
surface and a generally opposing base sheet having a bottom
surface. The cover sheet (e.g., the top surface of the cover
sheet), the base sheet (e.g., the bottom surface of the base
sheet), or both, may have a portion that is (or may be) generally
flat (e.g., have a generally planar surface), generally arcuate, or
any combination thereof. Preferably the base sheet and/or the
bottom surface of the base sheet includes a generally arcuate
portion or is generally arcuate, the top surface of the article is
generally planar (e.g., the cover sheet is generally flat), or
both. In various embodiments of the invention a generally planar
cover sheet may include one or more stiffening features (such one
or more ribs, dimples, chevrons, or other protrusions or recesses
as described herein) and/or one or more volume expansion features.
As described herein, a cover sheet may also be replaced by a second
base sheet. As such, the capsular structure may be define by two
base sheets that are the same or different.
[0055] The capsular structure may include one or more openings,
such as a fluid passages. For example, the capsular structure may
include one or more fluid passages so that a fluid, such as a heat
transfer fluid, can flow through the article without contacting the
thermal energy storage material. Without limitation, the capsular
structure may include a fluid passage having one or more features
described in paragraphs 7-12, 28-43, and 54-67, and FIGS. 1, 2, 3,
4, 5, 6, and 7 of U.S. Provisional Application No. 61/299,565
entitled "Thermal Energy Storage" and filed on Jan. 29, 2010,
incorporated herein by reference.
[0056] The cover sheet and the base sheet may include one or more
openings. The cover sheet and the base sheet may be arranged so
that at least one opening of the cover sheet overlaps at least one
opening of the base sheet. As such, the cover sheet and the base
sheet may have one or more corresponding openings. The cover sheet
has an outer periphery in the regions furthest from the center of
the cover sheet. The cover sheet may have one or more opening
peripheries in the region of the cover sheet near an opening
(preferably near the center) of the cover sheet. The base sheet has
an outer periphery in a region far from the center of the base
sheet and may also have an opening periphery near the opening
(preferably near the center) of the base sheet. Each of the cover
sheet and the base sheet may be sealingly attached to each other or
to one or more other optional sub-structures (such as an outer
ring) along the respective outer peripheries of the sheets, for
forming one or more sealed spaces therebetween. Each of the cover
sheet and the base sheet may be sealingly attached to each other or
to one or more other optional sub-structures (such as an inner
ring) along the respective opening peripheries of the sheets, for
forming one or more sealed spaces therebetween. Preferably the
cover sheet and the base sheet are sealingly attached to each other
along their respective outer peripheries, along at least one of
their respective corresponding opening peripheries, or both. Most
preferably the cover sheet and the base sheet are sealingly
attached to each other both along their respective outer
peripheries and along at least one of their respective
corresponding opening peripheries. It will be appreciated that the
cover sheet and the base sheet may also be sealingly attached to
each other or to one or more other optional sub-structures along
one or more additional regions (other than their peripheries) so
that a plurality of sealed spaces are formed.
[0057] The capsular structure may optionally include one or more
sub-structures that when sealingly attached to a base sheet and a
cover sheet forms one or more sealed spaces. Without limitation,
the sub-substructure, if employed, may include one or any
combination of the features described in U.S. Provisional
Application No. 61/299,565 entitled "Thermal Energy Storage" and
filed on Jan. 29, 2010, incorporated herein by reference. For
example, the base sheet, the cover sheet, or both may be attached
to one or more rings, such as one or more inner rings, one or more
outer rings, or both. The substructure, if employed, may include a
honeycomb or other open cell structure, such as described in
paragraph 83 of U.S. Patent Application Publication No.
2009-0250189 by Bank et al., published on Oct. 8, 2009,
incorporated herein by reference.
[0058] The thickness of the capsular structure is defined by the
average separation between the top surface of the article (e.g.,
the top surface of the cover sheet) and the bottom surface of the
article (e.g., the bottom surface of the base sheet). The article
may have a geometry sufficiently thin so that heat can be rapidly
provided from a fluid to thermal energy storage material and/or
rapidly removed from the thermal energy storage material to a
fluid. The article may have a thickness that is less than the
length or diameter of the article.
[0059] For example, ratio of the length or diameter of the article
to the thickness of the article may be about 2 or more, about 5 or
more, about 10 or more, or about 20 or more. Without limitation,
the ratio of the length or diameter of the article to the thickness
of the article may be about 1,000 or less, preferably about 300 or
less, and more preferably about 150 or less. Preferably, the
thickness of the article is 80 mm or less, more preferably about 20
mm or less, even more preferably about 10 mm or less, and most
preferably about 8 mm or less. The thickness of the article
preferably is greater than about 0.5 mm, more preferably greater
than about 1 mm.
[0060] The longest dimension of the article (e.g., the length or
diameter of the article) is typically much greater than the
thickness of the article so that the article can both have a large
volume (e.g., for containing a large volume of thermal energy
storage material), and a large surface area (e.g., for rapid
transfer of thermal energy). The longest dimension of the article
preferably is greater than about 30, more preferably greater than
about 50 mm and most preferably greater than about 100 mm. The
longest dimension is defined by the use, and can be any length that
meets the need for heat storage, heat transfer, or both, in a
particular use. The longest dimension of the article typically is
less than about 2 m (i.e., 2,000 mm), however articles having a
longest dimension greater than about 2 m may also be employed.
[0061] The article may have one or more side surfaces. For example
the article may have one or more side surfaces that are nonplanar.
The article may have a single side surface that is generally
arcuate, generally nonplanar, generally continuous, or any
combination thereof. Preferably the one or more side surfaces are
generally equidistant from a center of the article so that the
article can be placed in a container having a generally cylindrical
cavity with a cavity diameter that is only slightly larger than the
average diameter of the article. When the ratio of the cavity
diameter to the average diameter of the article is low, a large
amount of the cavity is occupied by the article. For example, the
ratio of the maximum diameter of the article to the average
diameter of the article may be less than about 1.8, preferably less
than about 1.2, more preferably less than about 1.1, and most
preferably less than about 1.05. It will be appreciated that the
ratio of the maximum diameter to the average diameter of the
article is about 1.0 or more (e.g., about 1.001 or more).
[0062] A large portion of the volume of the capsular structure is
the encapsulated volume (i.e., the volume of the one or more sealed
spaces) so that the article can contain a relatively large amount
of the thermal energy storage material. The total volume of the one
or more sealed spaces of the article is preferably at least about
50 volume percent, more preferably at least about 80 volume
percent, even more preferably at least about 85 volume percent and
most preferably about 90 volume percent based on the total volume
of the article. The total volume of the one or more sealed spaces
of the article is typically less than about 99.9 volume percent
based on the total volume of the article. The remaining volume, not
occupied by the thermal energy storage material, may include or
consist substantially entirely of the capsular structure, void
spaces (e.g., containing one or more gases), one or more structures
for improving the heat transfer between the thermal energy storage
material and the capsular structure, or any combination thereof.
Structures for improving heat transfer between the thermal energy
storage material and the capsular structure include any structure
formed of a material having a relatively high thermal conductivity
(e.g., relative to the thermal energy storage material) that is
capable of increases the rate of heat flow from the thermal energy
storage material to a heat transfer fluid. Preferable structures
for improving the rate of heat flow include fins, wire mesh,
protrusions into the sealed space, and the like.
[0063] The article preferably is easy to stack with other identical
shaped articles, or other articles having a generally mating
surface. For example, two articles to be stacked may have opposing
surfaces that are generally mating surfaces so that when stacked,
the two articles nest together. It will be appreciated that one
approach for stacking articles so that they easily nest together is
to select a shape (e.g., a shape of an arcuate surface, a shape of
the sealed spaces, or both) having a rotational symmetry of a high
order. The rotational symmetry may be about an axis in the stacking
direction (e.g., an axis through the fluid passage of the capsular
structure). The order of the rotational symmetry typically
describes the number of distinct rotations between the two surfaces
being stacked together in which they will nest together. The order
of the rotational symmetry of the article, the base sheet (e.g.,
the arcuate surface of the base sheet), or both, preferably is at
least 2, more preferably at least 3, even more preferably at least
5, and most preferably at least 7.
[0064] The article preferably has a capsular structure that is
difficult to bend. For example, the capsular structure may be free
of a cross-section in which a cover sheet and a base sheet are in
contact throughout most or even all of a length of the
cross-section (such as a diameter of the capsular structure). There
are various approaches that may be employed for assuring that the
capsular structure will be difficult to bend, including selecting
an arrangement of the capsules so that the order of rotational
symmetry is not an even number, selecting an arrangement of the
capsules so that there is no rotational symmetry, selecting an
arrangement of capsules including two or more rings of capsules
(such as concentric rings) that are rotated relative to each other
so that every radial section includes at least one sealed space, or
any combination thereof. It will be appreciated that other
geometries and other means may be employed to make the capsular
article resistant to bending. For example, the materials for the
capsular structure may be chosen to be generally stiff, the
structure may include one or more ribs (e.g., in a tangential
direction), and the like.
[0065] All of the thermal energy storage material of the article
may be in a single sealed space. The thermal energy storage
material of the article may optionally be divided between a
plurality of sealed spaces so that if a sealed space is punctured
or otherwise leaks, despite the improvements described herein, only
a portion of the thermal energy storage material can be removed. As
such, the number of sealed spaces in the article (e.g., sealed
spaces that contain thermal energy storage material) may be 1 or
more, 2 or more, 3 or more, 4 or more, or 5 or more. The upper
limit on the number of sealed spaces is practicality and for a
particular application is defined by the need of the application.
Nevertheless, the number of sealed spaces in the article typically
is less than 1,000. However, it will be appreciated that very large
articles may have 1,000 or more sealed spaces. For the same
reasons, the volume fraction of the thermal energy storage material
that is found in any single sealed compartment may be about 100%,
less than about 55%, less than about 38%, than about 29%, or less
than about 21%, based on the total volume of the thermal energy
storage material in the article. Typically a sealed space includes
at least 0.1 volume % of the thermal energy storage material in the
article. However, it will be appreciated that the article may
include one or more sealed spaces that are substantially or even
entirely free of the thermal energy storage material.
[0066] The sealed spaces may optionally be arranged in a pattern
which facilitates efficient stacking of the articles of the
invention and efficient energy transfer to and/or from the
capsules, such as a plurality of concentric rings, including an
innermost ring (e.g., a ring closest to an opening periphery) and
an outermost ring (e.g., a ring closest to the outer periphery),
each containing one or more sealed spaces. The sealed spaces in one
ring may have a generally repeating pattern. For example, each
sealed space or each groups of 2, 3, 4 or more sealed spaces in a
ring may have generally the same shape and size. The number of
sealed spaces in each ring may be the same or different. Preferably
the outermost ring has more sealed spaces than the innermost ring,
the average length of the sealed spaces of the outermost ring is
less than the average length of the sealed spaces of the innermost
ring (where the average length is measured in the radial direction
from the opening to the outer periphery), or both, so that the
volume variation between the sealed spaces of the outermost ring
and the innermost ring is reduced.
[0067] As discussed hereinafter, the article may be placed in a
container, such as a container having a generally cylindrical
shaped cavity. Preferably, the cavity may be only slightly greater
in dimension than the longest dimension of the article. For
example, the diameter of the cavity of the container may be only
slightly larger than the diameter of the capsular structure of the
article. The diameter of the cavity should be sufficiently large so
that the article can be inserted into the cavity. When the article
(or a stack of the articles) is placed in the container, it may be
desirable for a fluid to be capable of flowing between the outer
periphery of the article and an interior wall of the container.
This can be achieved by designing the relationship of the interior
of the container and the shape of the article to create and
maintain fluid flow paths. Any means of creating such fluid flow
paths may be used. As such, the article may optionally have one or
more indents along its periphery (e.g., the cover sheet and the
base sheet may have one or more corresponding indents along their
respective outer peripheries) so that a space is formed for flowing
a heat transfer fluid. Alternatively, or in addition, the cavity of
the container may have a surface with one or more grooves for
flowing a fluid between the outer periphery of the article and the
surface of the container. As another example, the diameter of the
article may be sufficiently small in relation to the diameter of
the interior of the cavity so that a fluid can flow along the
entire outer periphery of the article. For example, the article may
have one or more indents or the container may have one or more
grooves, for each sealed space in the outermost ring of sealed
spaces. An indent or a groove may have any shape, such as a
polygonal shape, an arcuate shape, a wedge shape, and the like,
provided it has a sufficient size to allow for the heat transfer
fluid to flow. If employed, the smallest dimension of the indents
and/or grooves is typically at least about 0.1 mm). It will be
appreciated that a combination of two or more means of creating a
fluid flow path may be used. For example, the article may have one
or more indents along its outer periphery and the article may have
a sufficiently small diameter so that fluid can flow along its
entire outer periphery when placed in a cavity.
[0068] The article for containing thermal energy storage material
includes a base sheet that is formed so that it includes one or
more troughs suitable for holding a liquid. The base sheet may used
in a process in which one or more troughs are filled with a thermal
energy storage material, covered with a generally flat cover sheet
and then joined to the cover sheet (preferably while the thermal
energy storage material is at least partially in a molten state).
The base sheet may optionally have one or more protrusions, so that
when the article is stacked with another article having a surface
that generally mates with the base sheet, the two articles only
partially nest. As such the one or more protrusions may function as
a spacer to separate the generally mating surfaces so that a fluid
(e.g., a heat transfer fluid) can flow between the mating surfaces.
If employed, the protrusions preferably cover only a small portion
of the surface are of the base sheet so that the one or more
protrusions do not substantially interfere with the flow of the
fluid. The height of the protrusions may be selected to define the
height (e.g., the average height) of the flow path between the two
generally mating surfaces.
[0069] The base sheet may additionally include one or more volume
expansion features and/or one or more stiffening features, such as
one or more ribs, one or more dimples, one or more chevrons, or any
combination thereof, that function to stiffen the base sheet. It
has been surprisingly observed that the troughs, the stiffening
features, the volume expansion features, or any combination thereof
of the base sheet may reduce the maximum stress on the base sheet
when an article containing a thermal energy storage material is
heated. For example the maximum stress, such as the maximum von
Mises stress, on a base sheet may be less than the maximum von
Mises stress of a flat cover sheet made of the same material (e.g.,
the same metal) and having the same thickness as the base sheet
when the thermal energy storage material in a sealed space is
heated. The relatively low stress in the base sheet may provide an
opportunity to reduce the weight of the article and/or increase the
amount of thermal energy storage material in the article by using a
base sheet having a lower thickness (e.g., a thickness that is less
than the thickness of the cover sheet).
[0070] It has also been surprisingly observed that the thickness of
the base sheet, the cover sheet, or both may be further reduced by
adding the optional stiffening features such as ribs, dimples, or
chevrons to the base sheet. If employed, the stiffening features
preferably have a sufficient size, shape and number so that the
maximum von Mises stress of the sheet (e.g., the base sheet or the
cover sheet) is reduced, preferably by about 2% or more, more
preferably by about 5% or more, and most preferably by about 10% or
more. The stiffening features may include features that are
protrusions (i.e., that go away from the sealed space), features
that are recesses (i.e., that go into the sealed space), or both.
Preferred stiffening features protrude or recess by a depth/height
of about 0.2 mm or more, more preferably about 0.4 mm or more, and
most preferably about 0.6 mm or more. Preferred stiffening features
protrude or recess by a depth/height of about 5 mm or less, more
preferably about 3 mm or less, and most preferably about 1 mm or
less.
[0071] When stacking articles, they may be arranged so that cover
sheets from two adjacent articles are at least partially in contact
with each other. It may be desirable for the two cover sheets to
have a large contact area so that they are in good thermal
communication and/or for there to be little gaps or spaces between
the two cover sheets so that space is not wasted. As such, the
cover sheets may only include recesses. Good contact between two
cover sheets may also be achieved by having cover sheets that are
generally mating surfaces. For example, a first cover sheet may
have one or more recesses that mate with one or more protrusions of
a second cover sheet and/or vice versa.
[0072] The base sheet and the cover sheet are attached so that a
sealed space is formed that includes a thermal energy storage
material. The attachment of the base sheet and the cover sheet may
include a primary seal around one or more (e.g., all) of the sealed
paces so that a sealed space is isolated from any other sealed
space and/or from regions outside of the article. The attachment of
the base sheet and the cover sheet may include one or more
secondary seals, such as a seal that isolates a sealed space from a
region outside of the article and/or from other sealed spaces in
the event that a primary seal fails.
[0073] Without limitation, preferable thermal energy storage
materials for the heat storage device include materials that are
capable of exhibiting a relatively high density of thermal energy
as sensible heat, latent heat, or preferably both. The thermal
energy storage material is preferably compatible with the operating
temperature range of the heat storage device. For example the
thermal energy storage material is preferably a solid at the lower
operating temperature of the heat storage device, is at least
partially a liquid (e.g., entirely a liquid) at the maximum
operating temperature of the heat storage device, does not
significantly degrade or decompose at the maximum operating
temperature of the device, or any combination thereof. The thermal
energy storage material preferably does not significantly degrade
or decompose when heated to the maximum operating temperature of
the device for about 1,000 hours or more, or even for about 10,000
hours or more.
[0074] The thermal energy storage material may be a phase change
material having a solid to liquid transition temperature. The solid
to liquid transition temperature of the thermal energy storage
material may be a liquidus temperature, a melting temperature, or a
eutectic temperature. The solid to liquid transition temperature
should be sufficiently high so that when the thermal energy storage
material is at least partially or even substantially entirely in a
liquid state enough energy is stored to heat the one or more
objects to be heated to a desired temperature. The solid to liquid
transition temperature should be sufficiently low so that the heat
transfer fluid, the one or more objects to be heated, or both, are
not heated to a temperature at which it may degrade. As such the
desired temperature of the solid to liquid transition temperature
may depend on the object to be heated and the method of
transferring the heat. For example, in an application that
transfers the stored heat to an engine (e.g., an internal
combustion engine) using a glycol/water heat transfer fluid, the
maximum solid to liquid transition temperature may be the
temperature at which the heat transfer fluid degrades. As another
example, the stored heat may be transferred to an electrochemical
cell of a battery using a heat transfer fluid where the heat
transfer fluid has a high degradation temperature, and the maximum
solid to liquid temperature may be determined by the temperature at
which the electrochemical cell degrades or otherwise fail. The
solid to liquid transition temperature may be greater than about
30.degree. C., preferably greater than about 35.degree. C., more
preferably greater than about 40.degree. C., even more preferably
greater than about 45.degree. C., and most preferably greater than
about 50.degree. C. The thermal energy storage material may have a
solid to liquid transition temperature less than about 400.degree.
C., preferably less than about 350.degree. C., more preferably less
than about 290.degree. C., even more preferably less than about
250.degree. C., and most preferably less than about 200.degree. C.
It will be appreciated that depending on the application, the solid
to liquid transition temperature may be from about 30.degree. C. to
about 100.degree. C., from about 50.degree. C. to about 150.degree.
C. from about 100.degree. C. to about 200.degree. C., from about
150.degree. C. to about 250.degree. C., from about 175.degree. C.
to about 400.degree. C., from about 200.degree. C. to about
375.degree. C., from about 225.degree. C. to about 400.degree. C.,
or from about 200.degree. C. to about 300.degree. C.
[0075] For some applications, such as transportation related
applications, it may desirable for the thermal energy material to
efficiently store energy in a small space. As such, the thermal
energy storage material may have a high heat of fusion density
(expressed in units of megajoules per liter), defined by the
product of the heat of fusion (expressed in megajoules per
kilogram) and the density (measured at about 25.degree. C. and
expressed in units of kilograms per liter). The thermal energy
storage material may have a heat of fusion density greater than
about 0.1 MJ/liter, preferably greater than about 0.2 MJ/liter,
more preferably greater than about 0.4 MJ/liter, and most
preferably greater than about 0.6 MJ/liter. Typically, the thermal
energy storage material has a heat of fusion density less than
about 5 MJ/liter. However, thermal energy storage materials having
a higher heat of fusion density may also be employed.
[0076] For some applications, such as transportation related
applications, it may be desirable for the thermal energy storage
material to be light weight. For example, the thermal energy
storage material may have a density (measured at about 25.degree.
C.) less than about 5 g/cm.sup.3, preferably less than about 4
g/cm.sup.3, more preferably less than about 3.5 g/cm.sup.3, and
most preferably less than about 3 g/cm.sup.3. The lower limit on
density is practicality. The thermal energy storage material may
have a density (measured at about 25.degree. C.) greater than about
0.6 g/cm.sup.3, preferably greater than about 1.2 g/cm.sup.3, and
more preferably greater than about 1.7 g/cm.sup.3.
[0077] The sealed spaces may contain any art known thermal energy
storage material. Examples of thermal energy storage materials that
may be employed in the thermal energy storage material compartments
include the materials described in Atul Sharma, V. V. Tyagi, C. R.
Chen, D. Buddhi, "Review on thermal energy storage with phase
change materials and applications", Renewable and Sustainable
Energy Reviews 13 (2009) 318-345, and in Belen Zalba, Jose Ma
Marin, Luisa F. Cabeza, Harald Mehling, "Review on thermal energy
storage with phase change: materials, heat transfer analysis and
applications", Applied Thermal Engineering 23 (2003) 251-283, both
incorporated herein by reference in their entirety. Other examples
of preferred thermal energy storage materials that may be employed
in the heat transfer device include the thermal energy storage
materials described in U.S. Patent Application Publication Nos:
2009/0211726 (entitled "Thermal Energy Storage Materials" and
published on Aug. 27, 2009) and 2009/0250189 (entitled "Heat
Storage Devices" and published on Oct. 8, 2009), and paragraphs
54-63 of U.S. Provisional Patent Application No. 61/299,565
(entitled "Thermal Energy Storage" and filed on Jan. 29, 2010).
[0078] The thermal energy storage material may include an organic
material, an inorganic material or a mixture of an organic and an
inorganic material that exhibits the solid to liquid transition
temperature, the heat of fusion density, or both, described
hereinbefore. Organic compounds that may be employed include
paraffins and non-paraffinic organic materials, such as a fatty
acid. Inorganic materials that may be employed include salt
hydrates and metallics. The thermal energy storage material may be
a compound or a mixture (e.g., a eutectic mixture) having a solid
to liquid transition at generally a single temperature. The thermal
energy storage material may be a compound or a mixture having a
solid to liquid transition over a range of temperatures (e.g., a
range of greater than about 3.degree. C., or greater than about
5.degree. C.).
[0079] Without limitation, the thermal energy storage material may
include one or more inorganic salts selected from the group
consisting of nitrates, nitrites, bromides, chlorides, other
halides, sulfates, sulfides, phosphates, phosphites, hydroxides,
carboxides, bromates, mixtures thereof, and combinations
thereof.
[0080] The thermal energy storage material may include (or may even
consist essentially of or consist of) at least one first metal
containing material, and more preferably a combination of the at
least one first metal containing material and at least one second
metal containing material. The first metal containing material, the
second metal containing material, or both, may be a substantially
pure metal, an alloy such as one including a substantially pure
metal and one or more additional alloying ingredients (e.g., one or
more other metals), an intermetallic, a metal compound (e.g., a
salt, an oxide or otherwise), or any combination thereof. One
preferred approach is to employ one or more metal containing
materials as part of a metal compound; a more preferred approach is
to employ a mixture of at least two metal compounds. By way of
example, a preferred metal compound may be selected from oxides,
hydroxides, compounds including nitrogen and oxygen (e.g.,
nitrates, nitrites or both), halides, or any combination thereof.
It is possible that ternary, quaternary or other multiple component
material systems may be employed also. The thermal energy storage
materials herein may be mixtures of two or more materials that
exhibit a eutectic.
[0081] The volume of the thermal energy storage material in the one
or more sealed spaces of the article is sufficiently high so that
the article can store a large amount of thermal energy. The ratio
of the volume of the thermal energy storage material contained in
the article to the total volume of the one or more sealed spaces,
the ratio of the volume of the thermal energy storage material to
the total volume of the article, or both (the volumes measured at a
temperature of about 25.degree. C., or at a temperature at which
the thermal energy storage material is a liquid) preferably is
greater than about 0.5, more preferably greater than about 0.7, and
most preferably greater than about 0.9. The ratio of the volume of
the thermal energy storage material contained in the article to the
total volume of the one or more sealed spaces, the ratio of the
volume of the thermal energy storage material to the total volume
of the article, or both (the volumes measured at a temperature of
about 25.degree. C., or at a temperature at which the thermal
energy storage material is a liquid) is typically less than about
1.0, and more typically less than about 0.995.
[0082] The sealed space may include a volume that contains a gas,
such as air, N.sub.2, or an inert gas such as He, Ar, and the like,
so that the thermal energy storage material can expand when heated.
For example, the sealed space may have a region that is free of
thermal energy storage material at a temperature of about
25.degree. C., so that upon heating the thermal energy storage
material above its liquidus temperature, the thermal energy storage
material can expand without forming a hole in the cover sheet or
base sheet or causing one or more sheets to delaminate. The volume
of a sealed space that is free of thermal energy storage material
(e.g., the volume of the sealed space that contains a gas) at
25.degree. C., may be at least about 0.5%, preferably at least
about 1%, and most preferably at least about 1.5%, based on the
total interior volume of the sealed space.
[0083] The thermal energy storage material, the sealed space, or
both may be substantially free of, or entirely free of materials
that undergo vaporization or sublimation when the article is used
to store heat so that the pressure in the sealed space is not
greatly increased. For example, the thermal energy storage
material, the sealed space, or both may be substantially free of
materials that undergo vaporization or sublimation at a temperature
from about 25.degree. C. to about 100.degree. C., preferably from
about 25.degree. C. to about 150.degree. C., more preferably about
25.degree. C. to about 200.degree. C., and most preferably from
about 25.degree. C. to about 300.degree. C. As such, the thermal
energy storage material, the sealed space, or both may be
substantially free of water. In applications that employ
temperatures of about 100.degree. C. or more for storing thermal
energy, it may be desirable for the sealed space to be
substantially free of, or even entirely free of water. If present
the concentration of water in the sealed space may be about 5 wt. %
or less, more preferably about 1 wt. % or less, even more
preferably about 0.2 wt. % or less, and most preferably about 0.1
wt. % or less.
[0084] FIG. 1 is a drawing that illustrates a portion of an article
2 having a capsular structure. A portion of the outer surface
(bottom surface) of the base sheet 12 of the article is shown in
FIG. 1. The article includes a plurality of capsules 10. As shown
in FIG. 1, the capsules 10 may be positioned in a periodic
arrangement 11. The base sheet may have one or more trough 8, such
as a trough that may be employed to hold the thermal energy storage
material before and/or during the attachment of a base sheet to a
cover sheet. The base sheet also includes a lip region 6. The lip
region may be employed to attach the base sheet to a cover sheet.
As such, the lip region may be a region that does is not covered
with thermal energy storage material when the base sheet and the
cover sheet are attached.
[0085] FIG. 2A is a cross-sectional view of an illustrative
capsular structure 2 that includes one or more sealed spaces 18.
FIG. 2B is a cross-sectional view of a single capsule , such as a
capsular structure having one capsule 10 or a portion of a capsular
structure 2 having a plurality of capsules 10. As illustrated in
FIGS. 2A and 2B, the capsule 10 may be a sealed space 18 that
contains a thermal energy storage material 16, and optionally a gap
20 or other space that is generally free of thermal energy storage
material. The article may include one or more primary seals 22,
such as a seal that isolates the sealed space 18 from a region
outside of the article 24, from other sealed spaces, or both. The
article may include one or more secondary seals 22' that may
isolate the sealed space in the event a primary seal 22 fails. As
illustrated in FIGS. 2A and 2B, the sealed space 18 may be formed
by attaching a base sheet 12 about a lip region 6 to a cover sheet
14 (e.g., a cover sheet that is generally flat). The base sheet may
also includes a trough region 8. The thickness 13 of the base sheet
may be reduced (e.g., relative to the thickness 15 of the cover
sheet) due to the stiffening of the base sheet by the troughs 8'.
The seals (e.g., the primary seal 11, the secondary seal 22', or
both) may be formed by welding the base sheet and cover sheet, such
as by laser welding.
[0086] The one or more sealed spaces may be prepared by joining a
metal cover sheet and a metal base sheet with one, two, or more
welds, wherein the welds completely encloses the one or more sealed
spaces. An individual sealed space may be prepared using a single
continuous weld, or a plurality of welds. The plurality of welds
may form a continuous perimeter. The plurality of welds may be
discontinuous. For example, an individual sealed space may have one
weld along an outer perimeter and a second weld along an inner
perimeter.
[0087] FIG. 3 is a schematic drawing of a portion of a formed sheet
40 (e.g., a base sheet 12) that may be employed in an article 2
having a plurality of sealed spaces. The formed sheet may have an
opening 46 (e.g., a generally circular opening) near the center of
the sheet. FIG. 3 shows only about 1/4 of the formed sheet 40 and
thus only 1/4 of the opening 46 is shown. FIG. 3 shows the bottom
surface 41 of the formed sheet 40. The formed sheet has a plurality
of trough regions 8 and a plurality of lip regions 6. The trough
regions preferably provides troughs 55 that are capable of
containing thermal energy storage material. The trough regions 8
may be arranged in a plurality of rings of troughs 50, 50', 50''.
As illustrated, the formed sheet may have an innermost ring of
troughs 50 and an outermost ring of troughs 50'. The formed sheet
may also have one or more additional rings of troughs 50'', between
the innermost and the outermost rings of troughs 50, 50'. As
illustrated in FIG. 3, some or all of the troughs in a ring, or
even some or all of the troughs in different rings may have about
the same shape, about the same volume, be substantially congruent,
or any combination thereof. It will be appreciated that the number
of troughs in the innermost ring of troughs may be more than, less
than or the same as the number of troughs in the outermost ring of
troughs. Preferably, the number of troughs in the innermost ring of
the formed sheet 40 is less than the number of troughs in the
outermost ring, as illustrated in FIG. 6. Some, or preferably all
of the troughs regions 8 have a lip region 6 around the trough
region. As such, a trough region 8 may be separated by the other
trough regions by a lip region 6. The formed sheet 40 may have an
outer periphery 45, an inner periphery 47, or both. As illustrated
in FIG. 3, the formed sheet may have one or more indents 51 near
the outer periphery 45. The one or more indents may be used for
flow channels or flow paths along the outer periphery 45.
Preferably the outer perimeter of the bottom surface of the formed
sheet 40 has a generally circular shape (excluding the optional one
or more indents 51). As illustrated in FIG. 3, the outer periphery
45, the inner periphery 47, and preferably both, may be lip regions
6.
[0088] FIG. 4A illustrates a portion of a cover sheet 14 having
chevrons 30. The dimensions (e.g., x, y, z, or any combination
thereof) in FIG. 4A may be in units of mm. The chevrons 30 may have
a periodicity (in one or more directions) of about 3 mm or more, a
periodicity of about 50 mm, or less, or both. The periodicity of
the chevrons may be sufficiently small so that the portion of a
cover sheet over an individual sealed space has a plurality of
chevrons 30. For example, the number of chevrons 30 over the region
of a cover sheet 14 over a single sealed space may be about 2 or
more, about 5 or more, about 10 or more about 20 or more, or about
30 or more. The chevrons 30 may have a periodicity of about 5 mm.
The chevrons 30 may have a depth of about 0.2 mm or more, a depth
of about 4 mm or less, or both. For example, the chevrons 30 may
have a depth of about 1 mm. It will be appreciated that chevrons
having a higher or lower periodicity and/or a higher or lower depth
may also be employed. The dimensions (e.g., x, y, z, or any
combination thereof) in FIG. 4A may be in any arbitrary units that
are the same or different, or may be in units of mm. The chevrons
may be in a section of the cover sheet that covers a sealed space,
in a region of a cover sheet that is away from sealed spaces, or
both. It will be appreciated that chevrons may be employed in a
base sheet, a cover sheet or both.
[0089] FIG. 4B is schematic view of an illustrative capsule 10
having a cover sheet 14 that includes dimples 32. FIG. 4C is a top
view of the portion of a cover sheet 14 over a single capsule, such
as the capsule illustrated in FIG. 4B. As illustrated in FIGS. 4Ba
and 4C, the cover sheet 14 may include one or more dimples 32, and
particularly one or more recessed dimples 33. The dimples 32 may be
in any arrangement. For example, the dimples may have a brick wall
pattern, so that adjacent rows of dimples are shifted. The dimples
preferably have a periodicity of about 1 mm or more, more
preferably about 2 mm or more, and most preferably about 3 mm or
more. The periodicity of the dimples preferably is about 30 mm or
less, more preferably about 15 mm or less, and most preferably
about 10 mm or less. The periodicity of the dimples may be
sufficiently small so that the portion of a cover sheet over an
individual sealed space has a plurality of dimples 32. For example,
the number of dimples 32 over the region of a cover sheet 14 over a
single sealed space may be about 2 or more, about 5 or more, about
10 or more about 20 or more, or about 30 or more. The dimples
preferably have a depth of about 0.1 mm or more, more preferably
about 0.2 mm or more, even more preferably about 0.3 mm or more,
even more preferably about 0.5 mm or more, and most preferably
about 0.5 mm or more. The dimples preferably have a depth of about
3 mm or less, more preferably about 2 mm or less, and most
preferably about 1 mm or less. It will be appreciated that dimples
having a higher or lower periodicity and/or a higher or lower depth
may also be employed. The dimples 32 may be in a section of the
cover sheet that covers a sealed space, in a region of a cover
sheet that is away from sealed spaces, or both. It will be
appreciated that dimples may be employed in a base sheet, a cover
sheet or both.
[0090] FIG. 4D shows an illustrative to view of a portion of a
sheet (e.g., a cover sheet 14) that includes stiffening features.
The stiffening features 34 may be arranged in a generally random
pattern. As illustrated in FIG. 4D, the stiffening features 34 may
have different shapes, different sizes, or both. The periodicity of
the stiffening features may be sufficiently small so that the
portion of a cover sheet 14 over an individual sealed space has a
plurality of stiffening features 34. For example, the number of
stiffening features 34 over the region of a cover sheet 14 over a
single sealed space may be about 2 or more, about 5 or more, about
10 or more about 20 or more, or about 30 or more.
[0091] FIGS. 5A, 5B, and 5C illustrate the pressure 36, 36', 36''
in a sealed space 18', 18''' at different temperatures and sealed
at different sealing temperatures. As illustrated in FIG. 5A, at
the sealing temperature, the pressure inside 36 and the pressure
outside 38 of the sealed space 18', 18'' may be about the same. As
illustrated in FIG. 5B, the pressure inside 36' the sealed space
18' may be higher than the external pressure 38 when the sealed
space 18' is sealed at a low temperature and the article 2 is
heated to a higher temperature. As illustrated in FIG. 5B, there
may be a net outward force 35 on the cover sheet 14 due to the
pressure difference when the temperature is greater than the
sealing temperature. FIG. 5C illustrates that the pressure inside
36'' the sealed space 18'' may be less than the external pressure
38 when sealing at a high temperature and then reducing the
temperature. As illustrated in FIG. 58, there may be a net inward
force 35 on the cover sheet 14 due to the pressure difference when
the temperature is below the sealing temperature.
[0092] FIGS. 6A, 6B, and 6C shows an illustrative example of a
sheet (e.g., a cover sheet) that includes a rib structure 39 that
includes protrusions and recesses. FIG. 6A is a topographical
drawing of the region of the sheet for a single capsule. FIG. 6B is
a photograph of a portion of a sheet including a plurality of the
features of FIG. 6A. FIG. 6C illustrates the effect of the
structural features on the forces on the sheet when a sealed space
including the sheet is heated. As illustrated in FIG. 6, the ribs
may be confined to the region of the top sheet that is around the
sealed space. For example, the cover sheet may have a lip region
that is free of the ribs or other stiffening features in the region
where the cover sheet is attached to a base sheet.
[0093] FIGS. 7A and 7B illustrate a sheet 60 (e.g., a base sheet
12) that includes volume expansion features 62 so that the sealed
space is capable of increasing in volume as the thermal energy
storage material in the sealed space expands, and decreasing in
volume as the thermal energy storage material contracts. FIG. 8A is
a schematic of a section of a base sheet 12 having a volume
expansion feature 62. As illustrated in FIG. 7A, the volume
expansion feature 62 may include one or more wrinkles, such as one
more convolutions 64. The volume expansion feature may include a
bellow. FIG. 7A illustrates a volume expansion feature 62 in a base
sheet 12. However, it will be appreciated that the base sheet 12,
the cover sheet 14 or both may include one or more volume expansion
features 62. The volume expansion feature may function by allowing
a sheet to reversibly contract into the sealed space. FIG. 7B is an
illustrative cross-section of a portion of a capsule 10 including
the sheet 60 having the volume expansion feature 62, a cover sheet
14, and the thermal energy storage material 16. The thermal energy
storage material 16 may be in a sealed space 18, which is sealed by
a primary seal 22, and preferably a secondary seal 22'.
[0094] FIG. 8 shows an illustrative relationship between the
expected peak Von Mises stress in a cover sheet when the capsule 10
is heated to about 250.degree. C. as a function of the thickness of
the cover sheet 15. FIG. 8 also shows the yield stress of the metal
employed in forming the cover sheet. At low thickness, the peak von
Mises stress is higher than the yield stress of the metal and the
cover sheet may yield or crack. At higher thicknesses, the peak von
Mises stress is lower than the yield stress of the metal and the
cover sheet does not yield or fail. FIG. 9 shows an illustrative
relationship between the expected peak Von Mises stress in a cover
sheet when the capsule is heated to about 250.degree. C. as a
function of the thickness of the cover sheet 15 for cover sheets
that are generally flat and for cover sheets that have the rib
structure shown in FIG. 6. The thickness of the cover sheet
required to prevent yielding of the cover sheet may be reduced when
a ribs structure is employed. As such, the rib structure of FIG. 6
may allow for articles and heat storage devices that are light
weight, contain a greater amount of thermal energy storage
material, or both.
[0095] FIG. 10 shows an illustrative relationship between the
expected peak Von Mises stress in a cover sheet when the capsule is
heated to about 250.degree. C. as a function of the thickness of
the cover sheet for cover sheets that are generally flat and for
cover sheets that have the rib structure shown in FIG. 6, the
chevron structure of FIG. 4A, and the dimple pattern of FIG. 4B.
The thickness of the cover sheet required to prevent yielding of
the cover sheet may be reduced when the different stiffening
structure are employed. As such, the structure of FIGS. 4A, 4B, and
6 may allow for articles and heat storage devices that are light
weight, contain a greater amount of thermal energy storage
material, or both.
[0096] FIG. 11 illustrates a portion of tooling 61 that may be
employed in preparing a sheet (e.g., a cover sheet 14) having one
or more stiffening features, such as one or more ribs. Such tooling
may be employed in an embossing process. It will be appreciated
that an embossing process may be a continuous process or a batch
process.
[0097] The articles containing the thermal energy storage material
preferably are capable of being stacked either with other identical
articles or with a second article having a generally mating surface
(such as a generally mating base sheet). The articles may be
stacked in axial layers with a space between adjacent axial layers
so that a heat transfer fluid can flow between the axial layers. An
axial layer will generally contain one, two or more article. An
axial layer (e.g., each axial layer) preferably contains one or two
articles. For example, an axial layer may have two articles that
are in contact on a surface, such as a base surface or a cover
surface, so that a fluid cannot generally flow between the two
articles). As such, some of the articles (e.g., each article except
the articles at an end of a stack) may have a first surface (e.g.,
a base surface) that is generally in complete contact with a
surface of a first adjacent article so that a fluid cannot flow
along the first surface, and a second surface that is separated
from a second adjacent article (e.g., having an opposing surface
that is generally a mating surface with the second surface) so that
a fluid can flow along some, most, or even all of the second
surface. The separation between two adjacent axial layers may be
due to any art known spacing means. By way of example, preferable
spacing means include one or more protrusions on a surface of at
least one of the articles, a spacer material between, the two
layers, a capillary structure between two layers, or any
combination thereof. Preferably the second surface of the article
has a generally arcuate shape and the article partially nests with
the second adjacent article. The spacing between two articles that
partially nest preferably is generally constant (except for the
protrusions or other spacers that cause the adjacent articles to be
separated). It will be appreciated that the stacking of the
articles may include a step of rotating an axial layer (e.g.,
rotating an article), or otherwise arranging it so that the axial
layer at least partially nests with an adjacent axial layer. The
flow of a fluid between two opposing surfaces of two adjacent axial
layers will generally be in a radial direction and may be described
as a generally radial flow. Each pair of axial layers that are
spaced apart will have a radial flow path. The stack of articles
will typically have a plurality of radial flow paths (e.g., 2, 3,
or more). Two or more (e.g., each radial flow path may have the
same flow length, the same thickness, the same cross-sectional
shape, or any combination thereof. For example, two or more (e.g.,
all) of the radial flow paths may be congruent. It will be
appreciated that if the opening (i.e., fluid passage) is at the
center of the article, the radial flow path may be generally
symmetric, irrespective of the flow direction.
[0098] When stacked (e.g., in a stack containing 3, 4 or more
articles), the articles preferably each have at least one opening
that corresponds with an opening from each of the other articles
(except possibly an article at one end of the stack), so that a
portion of a fluid can flow from a first article in the stack to a
last article in the stack by flowing through each of the
corresponding openings of the articles interposed between the first
and last article without flowing between adjacent articles (i.e.,
without a generally radial flow). The flow through the openings
will generally be in an axial direction and may be described as a
generally axial flow.
[0099] As described above, the stack of articles may define a
central axial flow path (e.g., through the central axis formed by
the openings of the articles) and one or more radial flow paths
that are generally perpendicular to the central axial flow
path.
[0100] The stack of articles will generally be tightly packed
(e.g., except for the radial flow paths) so that the stack of
articles is compact and contains a large amount of thermal energy
storage material. As such, the radial flow path has a height (in
the direction between the adjacent articles), e.g., an average
height, that is generally small. The height of the radial flow path
preferably is less than about 15 mm, more preferably less than
about 5 mm, even more preferably less than about 2 mm, even more
preferably less than about 1 mm, and most preferably less than
about 0.5 mm. The height of the radial flow path typically is large
enough so that the fluid can flow through the path. Typically the
height (e.g., the average height) of the radial flow path is
greater than about 0.001 mm (e.g., greater than about 0.01 mm).
[0101] FIG. 12 illustrates an aspect of the invention that includes
a plurality of articles 2, each having one or more sealed spaces 18
for containing a thermal energy storage material 16 arranged to
form a stack of articles 70. The articles 2 may include a formed
sheet, such as a base sheet 12 having a generally arcuate surface
41. The surface 41 of one article may generally mate with the
surface of a second article. The articles may be arranged so that
adjacent articles partially nest together. The articles illustrated
in FIG. 12 have an inner ring of 9 generally identical capsules and
an outer ring of 17 generally identical capsules. The articles
illustrated in FIG. 12 have a rotational symmetry of order 1 and
thus have only 1 position in which two facing articles will
partially nest. To facilitate in the stacking of articles, each
article may have one or more locating features. It will be
appreciated that articles with a higher order of symmetry may be
employed. For example, the article may have a single ring of
capsules (or even a single capsule), or the article may have a
first ring of capsules having an integer multiple of capsules
(e.g., 1, 2, 3, or more) for each capsule of a second ring of
capsules. As illustrated in FIG. 12, the articles 2 may have a
generally circular cross-section (e.g., in a direction
perpendicular to the stacking direction). The outer periphery of
each article may have a plurality of indents 51 that are large
enough to allow for a fluid flow. The articles 2 may have sealed
spaces 74 arranged in one or more concentric rings of sealed
spaces. Each article 2 may have a fluid passage 46. The fluid
passage 46 may be generally near the center of the articles 2 so
that when the articles are stacked (e.g., stacked in an axial
direction), an axial flow path 84 is formed. The axial flow path 84
preferably includes a fluid passage 46 of each article 2.
[0102] FIG. 13 illustrates an article 2 that includes an odd number
of capsules 10. The article may have an odd rotational symmetry, so
that it cannot be easily deformed about a diameter. The article 2
may have a generally circular cross-section with one or more
openings 46 in the center of the article. The opening 46 may be
generally circular. As illustrated in FIG. 13, one or more, or even
each of the capsules or sealed spaces may have a primary seal 22
that isolates the sealed space from the outside of the article. The
article may also have one or more secondary seals 22'. The
secondary seal may include a seal near an inner periphery 47 (i.e.,
an opening periphery) of the article, a seal near an outer
periphery 45 of the article, or both. The secondary seal 22' may be
sufficient to prevent leaking of a thermal energy storage 16
material from a sealed space 18 if a primary seal fails 22.
[0103] The articles (e.g., a stack of articles) described herein
may be employed in a heat storage device. The heat storage device
may include a container or other housing having one or more
orifices for flowing a heat transfer fluid into the container and
one or more orifices for flowing a heat transfer fluid out of the
container. The heat storage device has one or more heat transfer
fluid compartments. Preferably, the heat storage device includes a
single heat transfer fluid compartment. A heat transfer fluid
compartment may include or consist substantially of a contiguous
space in the container between the inlet and the outlet, where the
heat transfer fluid can flow. The container preferably is at least
partially insulated so that heat losses from the container to the
ambient may be reduced or minimized.
[0104] The heat storage device may be designed so that it contains
a large concentration of thermal energy storage material, so that
it can transfer thermal energy between a heat transfer fluid and
the thermal energy storage material rapidly and/or uniformly, so
that it is generally compact, so that it can store heat for a long
time, or any combination thereof.
[0105] The inside of the container of the heat storage device may
have any shape capable of holding a stack of articles. Preferably,
the shape of the inside of the container is such that the stack of
articles occupies a large portion of the interior volume of the
container. The ratio of the total volume of thermal energy storage
material (e.g., measured at about 25.degree. C.) contained in the
sealed spaces of the articles in the container to the total
interior volume of the container (e.g., at a temperature of about
25.degree. C.) may be greater than about 0.3, preferably greater
than about 0.5, more preferably greater than about 0.6, even more
preferably greater than about 0.7, and most preferably greater than
about 0.8. The upper limit on the volume of thermal energy storage
material in the container is the need for space for a heat transfer
fluid that contacts the articles for transferring thermal energy.
The ratio of the total volume of thermal energy storage material
(e.g., measured at about 25.degree. C.) contained in the sealed
spaces of the articles in the container to the total interior
volume of the container (e.g., at a temperature of about 25.degree.
C.) may be less than about 0.99, preferably less than about
0.95.
[0106] The heat storage device has a heat transfer fluid
compartment for flowing a capable of containing a heat transfer
fluid as it circulates through the device. The heat transfer fluid
compartment preferably is connected to one or more orifices (e.g.
one or more inlets) for flowing a heat transfer into the heat
transfer fluid compartment. The heat transfer fluid compartment
preferably is connected to one or more orifices (e.g., one or more
outlets) for flowing a heat transfer out of the heat transfer fluid
compartment. The heat transfer fluid compartment may be a space at
least partially defined by one or more heat transfer fluid
compartment walls, a space at least partially defined by one or
more articles, a space at least partially defined by a housing or
container of the heat storage device, or any combination
thereof.
[0107] The heat transfer fluid compartment defines the flow path of
a heat transfer fluid through the heat storage device. The heat
transfer fluid compartment includes a generally axial flow path
through the openings of the stack of articles. The heat transfer
fluid compartment includes a generally radial flow path between two
adjacent articles. It will be appreciated that the radial flow may
be an inward flow from an outer periphery to the opening of an
article, or an outward flow from an opening to the outer periphery
of an article. The heat transfer fluid compartment includes a flow
path having a generally axial component (and optionally a
tangential component) between an outer periphery of the article and
a wall of the container. Preferably the combined radial flow paths
have a relatively high hydraulic resistance. For example, the
combined radial flow paths has a hydraulic resistance that is
greater than (more preferably at least two times greater than) the
hydraulic resistance of the central axial flow path, the outer
axial flow path, or both.
[0108] The heat transfer fluid compartment preferably has
sufficient thermal communication with the sealed spaces containing
the thermal energy storage material so that it can remove heat or
provide heat to the thermal energy storage material. The heat
transfer fluid compartment preferably is in direct thermal
communication with one or more (or more preferably all) of the
sealed spaces. A direct thermal communication can be any path of
shortest distance between a sealed space and a portion of the heat
transfer fluid compartment that is free of a material having low
thermal conductivity. Low thermal conductivity materials include
materials having a thermal conductivity less than about 100 W/(mK),
preferably less than about 10 W/(mK), and more preferably less than
about 3 W/(mK). For example, the heat transfer fluid or the heat
transfer fluid compartment may contact a wall of one or more (or
preferably all) of the sealed. or be separated from the sealed
spaces substantially or entirely by materials having high thermal
conductivity (e.g., greater than about 5 W/(mK), greater than about
12 W/(mK), or greater than about 110 W/(mK).
[0109] The heat transfer fluid compartment preferably is in direct
thermal communication with one or more (or more preferably all) of
the sealed spaces in the heat storage device. A direct thermal
communication can be any path of shortest distance between a
thermal energy storage compartment and a portion of the heat
transfer fluid compartment that is free of a material having low
thermal conductivity. For example, the heat transfer fluid or the
heat transfer fluid compartment may contact a wall of one or more
(or preferably all) of the sealed paces (such as a base sheet or a
cover sheet), or be separated from the sealed spaces substantially
or entirely by materials having high thermal conductivity (e.g.,
greater than about 5 W/(mK), greater than about 12 W/(mK), or
greater than about 110 W/(mK). It will be appreciated that a very
thin layer (e.g., less than about 0.1 mm, preferably less than
about 0.01 mm, and more preferably less than about 0.001 mm) of a
material having a low thermal conductivity may be between the heat
transfer fluid compartment and a thermal energy storage material
compartment without appreciably affecting the heat transfer.
[0110] The size and shape of the sealed spaces and/or articles may
be chosen to maximize the transfer of heat to and from the phase
change material contained in the capsules. The average thickness of
the article may be relatively short so that the heat can quickly
escape from the center of the sealed space, The average thickness
of the article, sealed space, or both may be less than about 100
mm, preferably less than about 30 mm, more preferably less than
about 10 mm, even more preferably less than about 5 mm, and most
preferably less than about 3 mm. The average thickness of the
article, the sealed space, or both, may be greater than about 0.1
mm, preferably greater than about 0.5 mm, more preferably greater
than about 0.8 mm, and most preferably greater than 1.0 mm.
[0111] The articles preferably have a relatively high surface area
to volume ratio so that the area of contact with the heat transfer
fluid is relatively high. For example, the article may have a
surface that maximizes the contact with a heat transfer fluid
compartment, the article may have a geometry that maximizes the
transfer of heat between the capsule and the heat transfer fluid
compartment, or both. The ratio of the total surface area of the
interface between the heat transfer fluid compartment and the
articles in the heat storage device to the total volume of the
thermal energy storage material in the heat storage device may be
greater than about 0.02 mm.sup.-1, preferably greater than about
0.05 mm.sup.-1, more preferably greater than about 0.1 mm.sup.-1,
even more preferably greater than about 0.2 mm.sup.-1, and most
preferably greater than about 0.3 mm.sup.-1.
[0112] The heat storage device has a container for containing the
stack of articles. The stack of articles may be contained in one or
more cavities of the container. Without limitation, examples of
containers that may be employed include those described in U.S.
Patent Application Publication No. 2009-0211726 (published on Aug.
27, 2009), PCT Application No. PCT/US09/67823 (filed on Dec. 14,
2009), and U.S. Provisional Application No. 61/299,565 (filed on
Jan. 29, 2010). Preferable containers may have one or more orifices
(e.g., one or more inlets) for flowing a heat transfer fluid into
the cavity of the container and one or more orifices (e.g., one or
more outlets) for flowing a heat transfer fluid out of the cavity
of the container. The inlet and the outlet may be on the same side
or on different sides (e.g., opposing sides) of the heat storage
device. Other than the orifices, the container preferably is sealed
or constructed so that a fluid flowing through the container does
not leak out of the container, so that a fluid flowing through the
container may have a pressure greater than ambient pressure, or
both.
[0113] The heat storage device may be used in applications that
require storing heat for long periods of time, storing heat in a
generally cold environment (e.g., an environment having a
temperature less than about 0.degree. C., or even less than about
-30.degree. C.), or both. Preferably the heat stored in the heat
storage device is slowly lost to the environment. Therefore some
form of insulation is preferably used in the present invention. The
better the insulation of the system is, the longer is the storage
time.
[0114] Any known form of insulation which reduces the rate of heat
loss by the heat storage device may be utilized. For example, any
insulation as disclosed in U.S. Pat. No. 6,889,751, incorporated
herein of its entirety by reference, may be employed. The heat
storage device preferably is (thermally) insulated container, such
that it is insulated on one or more surfaces. Preferably, some or
all surfaces that are exposed to ambient or exterior will have an
adjoining insulator. The insulating material may function by
reducing the convection heat loss, reducing the radiant heat loss,
reducing the conductive heat loss, or any combination. Preferably,
the insulation may be through the use of an insulator material or
structure that preferably has relatively low thermal conduction.
The insulation may be obtained through the use of a gap between
opposing spaced walls. The gap may be occupied by a gaseous medium,
such as an air space, or possibly may even be an evacuated space
(e.g., by use of a Dewar vessel), a material or structure having
low thermal conductivity, a material or structure having low heat
emissivity, a material or structure having low convection, or any
combination thereof. Without limitation, the insulation may contain
ceramic insulation (such as quartz or glass insulation), polymeric
insulation, or any combination thereof. The insulation may be in a
fibrous form, a foam form, a densified layer, a coating or any
combination thereof. The insulation may be in the form of a woven
material, a knit material, a nonwoven material, or a combination
thereof. The heat transfer device may be insulated using a Dewar
vessel, and more specifically a vessel that includes generally
opposing walls configured for defining an internal storage cavity,
and a wall cavity between the opposing walls, which wall cavity is
evacuated below atmospheric pressure. The walls may further utilize
a reflective surface coating (e.g., a mirror surface) to minimize
radiant heat losses.
[0115] Preferably, a vacuum insulation around the heat storage
device and or the heat storage system is provided. More preferably,
a vacuum insulation as disclosed in U.S. Pat. No. 6,889,751,
incorporated by reference herein in its entirety, is provided.
[0116] The heat storage device may optionally include one or more
compaction means to a stack of articles so that the spacing between
layers is generally maintained. The compaction means may be any
means capable of applying a compressive force to the stack of
articles. The compressive force should be sufficiently high so that
two articles do not rotate relative to each other, do not move
axially relative to each other, or both. The compressive force may
be sufficiently low so that an article is not permanently deformed,
cracked, or both. Preferred means of compaction will allow for some
changes in the thickness of the articles as the temperature of the
thermal energy storage material changes, as the thermal energy
storage material changes between a solid and a liquid phase, or
both. By way of example, the one or more means of compaction may
include one or more springs above the stack of articles, one or
more springs below the stack of articles, or both. Without
limitation, a means of compaction such as a spring, may be employed
to reduce or minimize the change in the thickness of a radial flow
path between two adjacent articles when the thermal energy storage
material is heated, undergoes a phase transition (such as a solid
to liquid transition) or both.
[0117] The heat storage device may have a plurality of flow paths
for the flow of a heat transfer fluid through the device. Each flow
path may include at least one radial flow between two adjacent
articles. Preferably two or more (e.g., each) of the flow paths
through the heat storage device has a similar total length, a
similar total hydraulic resistance, or both. Without limitation,
the heat storage device may include one or more seals, one or more
plates, one or more connectors, or one or more flow paths for a
heat transfer fluid as described in U.S. Patent Application
Publication No. 2009-0211726 (published on Aug. 27, 2009), PCT
Application No. PCT/US09/67823 (filed on Dec. 14, 2009), and U.S.
Provisional Application No. 61/299,565 (filed on Jan. 29,
2010).
[0118] The capsular structure and the articles containing the
thermal energy storage material may be formed using any method that
provides for the encapsulation of the thermal energy storage
material. Without limitation, the process may employ one or any
combination of the following: cutting or punching an opening (e.g.,
a hole) through a cover sheet, cutting or punching an opening
(e.g., a hole) through a base sheet (e.g., a thin sheet such as a
foil), forming (e.g., thermoforming, stamping, embossing or
otherwise deforming) a base sheet to define a pattern in the sheet
including at least one depression or trough region, forming a base
sheet to define a pattern in the sheet including one or more lip
regions and one or more trough regions, cutting or punching an
outer periphery (e.g., a generally circular outer periphery) on a
base sheet, cutting or punching an outer periphery (e.g., a
generally circular outer periphery) on a cover sheet, filling a
trough (e.g., a trough formed from the base sheet) with a thermal
energy storage material, covering a trough (e.g., a filled trough)
with a cover sheet, sealingly attaching a cover sheet (e.g., to a
base sheet) so that one or more sealed spaces containing thermal
energy storage material are formed, sealingly attaching a base
sheet along an outer periphery, sealingly attaching a base sheet
along an opening periphery, sealingly attaching a cover sheet
(e.g., to a base sheet) along an opening periphery, or sealingly
attaching a cover sheet (e.g., to a base sheet) along an outer
periphery. The process of forming the article preferably includes a
step of stamping, embossing, or thermoforming a base sheet. The
process of forming the article may employ one or more of the
process steps for producing a capsule described in U.S. patent
application Ser. No. 12/389,598 entitled "Heat Storage Devices" and
filed on Feb. 20, 2009. The method for forming the article may
optionally include one or any combination of the following:
sealingly attaching a base sheet to one or more substructures such
as an inner ring, an outer ring, or both; sealingly attaching a
cover sheet to one or more substructures such as an inner ring, an
outer ring, or both; or cutting, stamping or punching one or more
indents along the outer periphery of a base sheet and/or a cover
sheet. FIG. 15 is a photograph of an illustrative tooling that may
be employed for embossing a sheet (e.g., a base sheet). FIG. 15
illustrates a sheet 5 placed in the tooling 61 prior to forming the
sheet 5 into a base sheet 12.
[0119] The process for preparing a cover sheet, a base sheet, or
both may include one or more steps of embossing or otherwise
forming the sheet so that it includes one or more stiffening
features such as one or more dimples, one or more ribs, one or more
chevrons, or any combination thereof.
[0120] The process for preparing an article may include a step of
filling a base sheet with a thermal energy storage material. The
base sheet may be filled when the thermal energy storage material
is in a solid state or in a molten state. Preferably the base sheet
is filled when the thermal energy storage material is in a molten
state. As such, the process may include a step of heating and/or
melting a thermal energy storage material.
[0121] The process for preparing an article may include a step of
joining a top sheet and a base sheet so that one or more sealed
spaces is formed. The step of joining may include a step of forming
a primary seal. Preferably the step of joining includes both a step
of forming a primary seal and a step of forming a secondary seal.
The step of joining preferably occurs while the thermal energy
storage material is in a molten state. For example, the step of
joining may occur when the thermal energy storage material is at a
temperature of about 100.degree. C. or more, about 150.degree. C.
or more, about 200.degree. C. or more, about 250.degree. C. or
more, or about 300.degree. C. or more.
[0122] The process for preparing an article may include a step of
partially joining a base sheet and a cover sheet to form a
partially sealed space that can contain a liquid when the base
sheet and the cover sheet are not in a generally horizontal
orientation. A space between the base sheet and the cover sheet may
be at least partially filled by inserting an end of a nozzle into
the space to be filled and pumping thermal energy storage material
(preferably in a molten state) through the nozzle and into the
partially sealed space. Thus, the space between a base sheet and a
cover sheet may be at least partially filled while the sheets are
in a troughs in the base sheet may be filled while the base sheet
is generally vertical. It will be appreciated that such an approach
for filling a space with thermal energy storage material may result
in a higher volume of thermal energy storage material. For example,
the percent of the volume of a sealed space that is occupied by air
or other gas may be about 8% or less, about 6% or less, about 5% or
less, about 4% or less, about 3% or less, about 2% or less, or
about 1% or less. This approach for filling a space may also be
used for filing a space between two base sheets. As such, the cover
sheet may be a second base sheet. After filling a space with
thermal energy storage material, the remainder of the primary seal
may be formed so that the filled space is a sealed space. With
respect to a secondary seal, if any, at least a portion of the
secondary seal (e.g., in the region where a nozzle is inserted) is
not formed until after the thermal energy storage material is
inserted into the space. An article having a plurality of sealed
spaces may be filled by a process including one or more of the
following steps: partially sealing one or more spaces (e.g., by
joining a base sheet and a cover sheet, or by joining two base
sheets) by forming a portion of a primary seal, inserting thermal
energy storage material into the one or more spaces, forming the
remainder of the primary seal (e.g., so that the space is sealed),
rotating the article being filled, inserting thermal energy storage
material into one or more additional spaces that have a portion of
a primary seal, and forming the remainder of the primary seal of
the one or more additional spaces.
[0123] FIG. 16 illustrates an example of an article 2 having one or
more (e.g., four) capsules 10 that have been filled with thermal
energy storage material and one or more (e.g., a fifth space) that
is being filled. The space being filled may have a partial primary
seal 74. The space being filled may optionally include a partial
secondary seal 75. The space being filled preferably has a fill
region 76 that does not have a complete primary seal 22 and does
not have a complete secondary seal 22'. The sealed space may be
filled using a nozzle 77 that is inserted or otherwise placed in
the fill region 76. It will be appreciated that the nozzle may be
placed in the fill region before, during, or after forming the
partial primary seal 74. As illustrated in FIG. 16, a nozzle 77 may
be may be inserted into the top of the space being filled, so that
the thermal energy storage material 16 does not leak out of fill
region 76. After inserting the thermal energy material 16 into the
space being filled, the process may include one or more of the
following steps: removing the nozzle (preferably before rotating
the article), forming the remainder of the primary seal (preferably
before rotating the article), or forming a secondary seal or the
remainder of a secondary seal. As such, the article may be prepared
using a machine that is capable of 1) forming a partial primary
seal between two sheets (e.g., by laser welding the two sheets), 2)
injecting thermal energy storage material (e.g., in a molten state)
into a space between the two sheets, 3) completing the primary
seal. If a plurality of sealed spaces are desired, the process may
include one or more steps of rotating the sheets so that another
space between the sheets can be filled.
[0124] Suitable sheets for encapsulating the thermal energy storage
material include any thin metal sheets (e.g., metal foil) that are
durable, corrosion resistant, or both, so that the sheet is capable
of containing the thermal energy storage material, preferably
without leakage. The metal sheets may be capable of functioning in
a vehicle environment with repeated thermal cycling for more than 1
year and preferably more than 5 years. The metal sheet may
otherwise have a substantially inert outer surface that contacts
the thermal energy storage material in operation. The outer surface
of the metal sheet that contacts the thermal energy storage
material should include or consist essentially of one or more
materials that do not significantly react with, corrode, or both,
when contacted with the thermal energy storage material. Without
limitation, exemplary metal sheets that may be employed include
metal sheets having at least one layer of brass, copper, aluminum,
nickel-iron alloy, bronze, titanium, stainless steel or the like.
The sheet may be a generally noble metal or it may be one that
includes a metal which has an oxide layer (e.g. a native oxide
layer or an oxide layer which may be formed on a surface). One
exemplary metal sheet is an aluminum foil which comprises a layer
of aluminum or an aluminum containing alloy (e.g. an aluminum alloy
containing greater than 50 weight percent aluminum, preferably
greater than 90 weight percent aluminum). Another exemplary metal
sheet is stainless steel. Preferable stainless steels include
austenitic stainless steel, ferritic stainless steel or martensitic
stainless steel. Without limitation, the stainless steel may
include chromium at a concentration greater than about 10 weight
percent, preferably greater than about 13 weight percent, more
preferably greater than about 15 weight percent, and most
preferably greater than about 17 weight percent. The stainless
steel may include carbon at a concentration less than about 0.30
weight percent, preferably less than about 0.15 weight percent,
more preferably less than about 0.12 weight percent, and most
preferably less than about 0.10 weight percent. For example,
stainless steel 304 (SAE designation) containing 19 weight percent
chromium and about 0.08 weight percent carbon. Preferable stainless
steels also include molybdenum containing stainless steels such as
316 (SAE designation). The metal sheet may have any art known
coating that may reduce or eliminate the corrosion of the metal
sheet.
[0125] The metal sheet has a thickness sufficiently high so that
holes or cracks are not formed when forming the sheet, when filling
the capsules with thermal energy storage material, during use of
the capsules, or any combination thereof. For applications such as
transportation, the metal sheet preferably is relatively thin so
that the weight of the heat storage device is not greatly increased
by the metal sheet. The thickness of the metal sheet may be greater
than about 10 .mu.m, preferably greater than about 20 .mu.m, and
more preferably greater than about 50 .mu.m. The metal sheet may
have a thickness less than about 3 mm, preferably less than 1 mm,
and more preferably less than 0.5 mm (e.g., less than about 0.25
mm).
[0126] FIG. 14 illustrates a cross-section of an exemplary heat
storage device 80 having a plurality of articles 2'', and 2''' each
having thermal energy storage material 16 encapsulated in a
plurality of sealed spaces 18. The articles are arranged in an
insulated container 82 which may have a generally cylindrical
shape. The device includes an article 2'' having a first adjacent
article 2'''(a) and a second adjacent article 2'''(b). The article
2'' and its first adjacent article 2'''(a) may be arranged with the
top surfaces (i.e., exterior surfaces) of their respective flat
cover sheets generally in contact. The article 2'' and the second
adjacent article 2'''(b) may have generally mating surfaces (e.g.,
the exterior surfaces of their respective base sheets may be
generally mating surfaces) and may be arranged so that they
partially nest together. A spacer (not shown) may be used to
maintain a distance between the article 2'' and its second adjacent
article 2'''(b) so that a heat transfer fluid can flow through a
radial flow path 83 in a generally radial direction between the two
articles, 2'' and 2'''(b). The space between the article 2'' and
the second adjacent article 2'''(b) may be formed from one of the
sheets of the article 2. As illustrated in FIG. 14, each article
may have a surface (e.g., a surface of the base sheet) that is
capable of contacting a heat transfer fluid so that the heat
transfer fluid can be in direct contact with each article and
preferably each sealed space. As illustrated in FIG. 14, each
radial flow path 83 may have the same length, the same
cross-section, or even may be congruent. Each article 2 may have an
opening 46 near its center. The openings may be part of a
compartment that allows a heat transfer fluid to flow through the
device. The articles 2'' and 2''' may be arranged so that their
openings form a central axial flow path 84. The space between the
outer periphery of the articles 2'' and 2''' and the interior
surface of the container 85 is also part of the heat transfer fluid
compartment and forms an outer axial flow path 86. The heat storage
device may have a first orifice 87 that is in fluid connection with
a central axial flow path 84. The heat storage device 80 may have a
first seal or plate 88 that separates a first orifice 87 from the
outer axial flow path 86. The container 82 may have a second
orifice 89 which may be on the same side of the container as the
first orifice 87, or on a different side of the container, as
illustrated in FIG. 14. The heat storage device may have a second
seal 90 that separates the second orifice 89 from the central axial
flow path. The first seal, the second seal, or both may prevent a
fluid from flowing between the two axial flow paths 84 and 86,
without flowing through a radial flow path 83. The container 82
preferably is insulated. For example, the container may have an
inner wall 91 and an outer wall 92. The space between the two walls
93 may be evacuated or filled with an insulating material having
low thermal conductivity. The device may also have one or more
springs, such as one or more compression springs 94, that exert a
compressive force on the stack of articles.
[0127] FIG. 14 illustrates a heat storage device 80 having two
orifices 87 and 89 on one side of the container. Such a device may
employ a tube 95 that is connected to the first orifice 87 for
flowing the fluid between the first orifice and a region 96 of the
central axial flow path 84 furthest from the first orifice. With
reference to FIG. 14, the first seal 88 and the second seal 90 may
be employed to prevent a fluid from flowing from the first orifice
87 to the second orifice 89 without first flowing through a radial
flow path 83. By selecting the sizes for the two axial flow paths
84 and 86, the heat storage device 80 may be characterized as a
Tichelmann system.
[0128] The pressure in one or more, or even all of the sealed
spaces may be less than atmospheric pressure, e.g. under a vacuum,
when the temperature is about 25.degree. C. For example, the
pressure in a sealed space at 25.degree. C. may be preferably about
600 Torr or less, about 500 Torr or less, about 400 Torr or less,
about 300 Torr or less, or about 100 Torr or less. A vacuum in a
sealed space may be a result of applying a vacuum when sealingly
joining the cover sheet and the base sheet, a result of sealingly
joining the cover sheet and the base sheet when the thermal energy
storage material is at an elevated temperature, or both. For
example, the process of sealingly joining the base sheet and the
cover sheet may include a step of applying a vacuum of about 600
Torr or less, about 500 Torr or less, about 400 Torr or less, about
300 Torr or less, about 200 Torr or less, about 100 Torr or less,
or about 50 Torr or less to a trough region of a base sheet.
[0129] The heat storage device may be used in a heat storage system
that employs one or more heat transfer fluids for transferring heat
into the heat storage device, for transferring heat out of the heat
storage device, or both.
[0130] The heat transfer fluid used to transfer heat into and/or
out of the thermal energy storage material may be any liquid or gas
so that the fluid flows (e.g., without solidifying) through the
heat storage device and the other components (e.g., a heat
providing component, one or more connecting tubes or lines, a heat
removing component, or any combination thereof) through which it
circulates when it is cold. The heat transfer fluid may be any art
known heat transfer fluid or coolant that is capable of
transferring heat at the temperatures employed in the heat storage
device. The heat transfer fluid may be a liquid or a gas.
Preferably, the heat transfer fluid is capable of flowing at the
lowest operating temperature that it may be exposed to during use
(e.g., the lowest expected ambient temperature). For example, the
heat transfer fluid may be a liquid or gas at a pressure of about 1
atmosphere pressure and a temperature of about 25.degree. C.,
preferably about 0.degree. C., more preferably -20.degree. C., and
most preferably at about -40.degree. C. Without limitation, a
preferred heat transfer fluid for heating and/or cooling the one or
more electrochemical cells is a liquid at about 40.degree. C.
[0131] The heat transfer fluid should be capable of transporting a
large quantity of thermal energy, typically as sensible heat. The
heat transfer fluid may have a specific heat (measured for example
at about 25.degree. C.) of at least about 1 J/gK, preferably at
least about 2 J/gK, even more preferably at least about 2.5 J/gK,
and most preferably at least about 3 J/gK. Preferably the heat
transfer fluid is a liquid.
[0132] Heat transfer fluids and working fluids that may be employed
include those described in U.S. Patent Application Publication
2009-0250189 (published on Oct. 8, 2009) and PCT Application No.
PCT/US09/67823 (filed on Dec. 14, 2009. For example, any art known
engine coolant may be employed as the heat transfer fluid. The
system preferably employ a single heat transfer fluid for
transferring heat into the thermal energy storage material in the
heat storage device and for removing heat from the thermal energy
storage material in the heat storage device. Alternatively, the
system may employ a first heat transfer fluid for transferring heat
to the thermal energy storage material and a second heat transfer
fluid for removing heat from the thermal energy storage
material.
[0133] Without limitation, heat transfer fluids which may be used
alone or as a mixture include heat transfer fluids known to those
skilled in the art and preferably includes fluids containing water,
one or more alkylene glycols, one or more polyalkylene glycols, one
or more oils, one or more refrigerants, one or more alcohols, one
or more betaines, or any combination thereof.
[0134] The heat storage system may optionally include one or more
heaters. The heater may be any heater that is capable of increasing
the temperature of the thermal energy storage material in the heat
storage device to a temperature above its transition temperature.
The heater may be any heater that converts energy (e.g., electrical
energy, mechanical energy, chemical energy, or any combination
thereof) into heat (i.e., thermal energy). The one or more heaters
may be one or more electric heaters. The one or more heaters may be
employed to heat some or all of the thermal energy storage in the
heat storage device. Preferably the system includes one or more
heaters that are in thermal communication with a heat storage
device. For example, the system may include one or more heaters
within the insulation of a heat storage device. An electric heater
may employ electricity from one or more electrochemical cells, from
an external source, or both. For example, when a vehicle is plugged
into an outlet connected to a stationary object, the heat storage
device may be maintained at a temperature above the liquidus
temperature of the thermal energy storage material in the heat
storage device using the electricity form an external source. When
the vehicle is not plugged into an outlet connected to a stationary
object, the heat storage device may be maintained at a temperature
above the liquidus temperature of the thermal energy storage
material in the heat storage device using electricity generated
from an electrochemical cell.
[0135] The heat storage device may be used in a process for heating
one or more components. The process may include flowing a heat
transfer fluid through the heat transfer device. The step of
flowing a heat transfer fluid through the heat storage device may
include flowing a heat transfer fluid having an initial temperature
through an inlet of the device; flowing the heat transfer fluid
through an axial flow path so the heat transfer fluid can be
divided into a plurality of radial flow paths; flowing the heat
transfer fluid through a radial flow path so that it can remove
heat from the thermal energy storage material, wherein the thermal
energy storage material has a temperature greater than the initial
temperature of the heat transfer fluid; flowing the heat transfer
fluid through a different axial flow path so that a plurality of
radial flow paths can recombine; flowing the heat transfer fluid
having an exit temperature through an outlet of the device; or any
combination thereof. Preferably the heat transfer fluid exit
temperature is greater than the initial temperature of the heat
transfer fluid. The process for heating one or more components may
employ a flow path through the heat storage device including one of
a selection of radial flow path and two axial flow paths, the flow
path having a total flow length, wherein the total flow length is
generally constant for the different radial flow paths.
[0136] The heat storage device and/or the heat storage system may
characterized as having a relatively high power (e.g., as measured
during the initial 30 or 60 seconds of heating) so that it can
rapidly heat a component, such as an internal combustion engine.
The heat storage device and/or the heat storage system may be
characterized by an average power greater than about 5 watts,
preferably greater than about 10 watts, more preferably greater
than about 15 watts, and most preferably greater than about 20
watts.
[0137] The heat storage device and/or the heat storage system may
be characterized as having a relatively high power density, so that
it can hold a large quantity of thermal energy in a relatively
small compartment. For example, the heat storage device and/or the
heat storage system may be characterized as having a power density
greater than about 4 kW/L, preferably greater than about 8 kW/L,
more preferably greater than about 10 kW/L, and most preferably
greater than about 12 kW/L.
[0138] The heat storage device and/or the heat storage system may
be characterized as having a relatively low pressure drop of the
heat transfer fluid (measured at a heat transfer fluid flow rate of
about 10 L/min). For example, the heat storage device and/or the
heat storage system may be characterized as having a heat transfer
fluid pressure drop less than about 2.0 kPa, preferably less than
about 1.5 kPa, more preferably less than about 1.2 kPa, and most
preferably less than about 1.0 kPa.
[0139] By way of example, the thermal energy storage system may be
employed in a transportation vehicle (e.g., an automotive vehicle)
for storing energy from an engine exhaust gas. When the engine
produces exhaust gas, a bypass valve may either direct the flow of
the gas through the heat storage device so that the heat storage
device is charged, or through a bypass line to prevent the heat
storage device from overheating. When the engine is shut down, e.g.
during a period when the vehicle is parked, a substantial portion
of the heat stored in the heat storage device may be retained for a
long time (e.g., due to vacuum insulation surrounding the heat
storage device). Preferably at least 50% of the thermal energy
storage material in the heat storage device remains in a liquid
state after the vehicle has been parked for 16 hours at an ambient
temperature of about -40.degree. C. If the vehicle is parked for a
long enough time (e.g., at least two or three hours) for the engine
to cool down substantially (e.g., so that the difference in
temperature between the engine and the ambient is less than about
20.degree. C.), the heat stored in the heat storage device may be
discharged into the cold engine or other heat recipient indirectly
by flowing a heat transfer fluid (such as the engine coolant)
through the heat exchanger that includes the condenser for the
working fluid. The working fluid is circulated in a capillary
pumped loop using the capillary structure inside the heat storage
device where the working fluid is vaporized. The heat from the
working fluid is transferred to the engine coolant in the heat
exchanger. By employing the heat storage device, heat that
otherwise would be wasted may be captured during a previous trip to
mitigate cold start and/or provide instant cockpit heating.
[0140] The transfer of heat using the working fluid may begin by
opening the working fluid valve (i.e., the discharge valve). The
sealed working fluid reservoir connected to the loop via an
additional liquid line serves to accommodate changes in the working
fluid liquid volume inside the loop without substantial pressure
changes. Once sufficient or all useful heat is transferred from the
heat storage device, the discharge valve may close. The remaining
working fluid in the heat storage device may evaporate (e.g., from
heat remaining in the heat storage device or when the heat storage
device begins to charge) and then condenses in the condenser. As
the heat storage device becomes evacuated of the working fluid, the
liquid level of the working fluid level may change (e.g.,
rise).
[0141] The heat storage device may optionally be a cross-flow heat
exchanger (i.e., having a flow direction for the working fluid and
a perpendicular flow direction for the flow of the exhaust gas).
For example, during operation, the heat storage device may include
three chambers occupied by 1) exhaust gas; 2) stagnant phase change
material (e.g., inside capsules, such as a blisters pack); and 3)
working fluid. All three chambers are kept separate by thin walls
made of an appropriate material, preferably stainless steel.
Exhaust gas may flow between the surfaces (e.g., the curved
surfaces) of the capsules of phase change material inside blisters,
and the working fluid may flow between different surfaces (e.g.,
flat surfaces) of the capsules of phase change material inside
blisters in a direction that is generally perpendicular to the
exhaust gas flow direction. The liquid working fluid entering its
chamber preferably wets a capillary structure (e.g., a metal wick)
and gets transported up against the combined forces of gravity and
vapor pressure by the capillary forces acting upon the working
fluid liquid menisci formed inside the capillaries. This flow is
sustained by continuous evaporation of the liquid using the heat
drawn from the phase change material inside blisters. The vapor of
working fluid leaves the capillary structure and escapes to the top
of the device via vapor channels which may be interdigitated
between columns of the capillary structure squeezed between the
surfaces (e.g., the flat surfaces) of the capsules of phase change
material inside blisters. The vapor of working fluid flows into the
condenser where it transfers its heat of vaporization and sensible
heat to the cold coolant and becomes liquid again to return to the
heat storage device and continue its circulation in the loop, being
pumped only by the capillary forces existing inside the capillary
structure (e.g., metal wick) that is partially impregnated by
liquid working fluid. All columns of the capillary structure may be
connected to a common porous base. Such a porous base may be
employed to distribute the liquid working fluid entering from the
bottom of the device to the different columns.
[0142] Furthermore, the present invention may be used in
combination with additional elements/components/steps. For example,
absorption or adsorption cycle refrigeration system for air
conditioning may be used as the heat recipient instead of or in
addition to the cold coolant (e.g., the condenser may serve also as
an evaporator for the refrigerant circulating inside an air
conditioner's fluid loop). In another application, a steady-state
waste heat recovery system using a heat engine, e.g. a Rankine
cycle, can be constructed so that it uses the same or different
capillary pumped loop working fluid and adds a mechanical power
generating turbine to the vapor line between the heat storage
device and the condenser, (e.g., to overcome high vapor pressure
upstream from the turbine), and/or adds a liquid pump to the liquid
line between the condenser and heat storage device. The above
turbine can convert a part of the captured from the exhaust gas
waste heat into useful mechanical or electrical work and thus
improve the overall fuel efficiency of the vehicle.
EXAMPLES
[0143] Example 1 is an article including 7 sealed spaces containing
thermal energy storage material and suitable for heat storage. The
packs are formed by filling a base sheet having 7 troughs with a
thermal energy storage material. Each trough is capable of
containing about 7 cm.sup.3 of a liquid. The base sheet is covered
with a flat cover sheet. The base sheet and the cover sheet are
made of stainless steel 304 and have a thickness of about 0.102 mm.
The thermal energy storage material is a metal salt and has a
liquidus temperature of about 195.degree. C. The thermal energy
storage material is anhydrous or has a moisture concentration of
about 0.01 wt. % or less. The two sheets are joined while the
thermal energy storage material is in a solid state (about
23.degree. C.). A primary seal is provided by laser welding
together the base sheet and the cover sheet about the periphery of
each sealed space. When heated to a temperature of about
250.degree. C., the sealed space has an internal pressure of about
69 kPa (about 10 psi).
Thermal Cyclic Testing
[0144] About 10 articles of Example 1 are stacked and placed in a
container having an inlet and an outlet. The inlet is connected to
a hot reservoir of a heat transfer fluid at a temperature of about
250.degree. C. and a cold reservoir of a heat transfer fluid at a
temperature of about 15.degree. C. The heat transfer fluid is
allowed to flow through the container until the temperature of the
thermal energy storage material is about 240.degree. C., then the
cold heat transfer fluid is allowed to flow through the container
until the temperature of the thermal energy storage material is
about 25.degree. C. The temperature of the thermal energy storage
material is cycled about every 5 minutes for about 1,000
cycles.
[0145] One or more sealed spaces of Example 1 rupture and/or
develop a leak in the primary seal during the thermal cyclic
testing prior to reaching 1,000 cycles. Thermal energy storage
material leaks out of one or more sealed spaces and Example 1 fails
the thermal cycling test.
Heat Test
[0146] An article of Example 1 is placed in an oven at a
temperature of about 400.degree. C. for about 30 minutes. The
article is then evaluated to determine if there are any leaks or
ruptures that would allow thermal energy storage material to leak
out of the article. One or more leaks and/or ruptures are observed
and Example 1 fails the heat test.
[0147] Example 2 is an article including 7 sealed spaces prepared
using the method of Example 1, except that a secondary seal is
prepared by laser welding the base sheet and the cover sheet near
their outer peripheries and near their opening peripheries. The
articles are tested using the same method as described for Example
1. The maximum von Mises stress is above the yield stress of the
foil. During the thermal cycling, the primary seal fails around one
or more sealed spaces. The secondary seal does not fail after 1,000
thermal cycles and the thermal energy storage material does not
leak out of the article.
[0148] Another article of Example 2 is tested by heating to
400.degree. C. At 400.degree. C., one or more primary seals fail.
However, the secondary seal does not fail and thermal energy
storage material does not leak.
[0149] Example 3 is an article including 7 sealed spaces prepared
using the method of Example 1, except the base sheet and the cover
sheet both use foils having a thickness of about 0.204 mm. The
articles are tested using the same method as described for Example
1. The maximum von Mises stress is below the yield stress of foil.
The primary seal does not fail after 1,000 thermal cycles and the
thermal energy storage material does not leak out of the
article.
[0150] Another article of Example 3 is tested by heating to
400.degree. C. for 20 minutes. At 400.degree. C., none of the seals
fail and the thermal energy storage material does not leak.
[0151] Example 4 is an article including 7 sealed spaces prepared
using the method of Example 1, except the cover sheet uses a foils
having a thickness of about 0.204 mm. The articles are tested using
the same method as described for Example 1. The maximum von Mises
stress is reduced to about 180 MPa, below the yield stress of foil.
The primary seal does not fail after 1,000 thermal cycles and the
thermal energy storage material does not leak out of the
article.
[0152] Another article of Example 4 is tested by heating to
400.degree. C. for 20 minutes. At 400.degree. C., none of the seals
fail and the thermal energy storage material does not leak.
[0153] Example 5 is an article including 7 sealed spaces prepared
using the method of Example 1, except the cover sheet is embossed
so that the cover sheet over each sealed space containing thermal
energy storage material has about 15 ribs including both indentions
and protrusions each having a depth of 0.1 to 0.5 mm. The articles
are tested using the same method as described for Example 1. The
maximum von Mises stress is about 233 MPa, below the yield stress
of foil. The primary seal does not fail after 1,000 thermal cycles
and the thermal energy storage material does not leak out of the
article. It will be appreciated that one, two, or more ribs may be
employed and that ribs may be indentions, protrusions, or both.
[0154] Another article of Example 5 is tested by heating to
400.degree. C. for 20 minutes. At 400.degree. C., none of the seals
fail and the thermal energy storage material does not leak.
[0155] Example 6 is an article including 7 sealed spaces prepared
using the method of Example 1, except the cover sheet is embossed
so that a sealed space including thermal energy storage material
has about 34 dimples that recess about 0.6 mm into the sealed
space. The dimples in the cover sheet are in a brickwall pattern as
shown schematically in FIG. 4B. The articles are tested using the
same method as described for Example 1. The maximum von Mises
stress is about 590 MPa and is above the yield stress of foil. The
primary seal fails during the thermal cycling and the thermal
energy storage material leaks out of the article. It will be
appreciated that fewer or more dimples may be employed and that the
dimples may be deeper or shallower.
[0156] Another article of Example 6 is tested by heating to
400.degree. C. for 20 minutes. At 400.degree. C., the seals fail
and the thermal energy storage material leaks.
[0157] Example 7 is an article including 7 sealed spaces prepared
using the method of Example 6, except the cover sheet is made of a
foil having a thickness of about 0.153 mm. The articles are tested
using the same method as described for Example 1. The maximum von
Mises stress is about 282 MPa and is below the yield stress of
foil. The primary seal does not fail during the thermal cycling and
the thermal energy storage material does not leak out of the
article after 1,000 thermal cycles.
[0158] Another article of Example 7 is tested by heating to
400.degree. C. for 20 minutes. At 400.degree. C., the seals do not
fail and the thermal energy storage material does not leak.
[0159] Example 8 is an article including 7 sealed spaces prepared
using the method of Example 1, except the cover sheet is embossed
with a plurality of chevrons that include recesses and protrusions
of about 0.5 mm. The chevrons in the cover sheet are in a repeating
pattern as shown schematically in FIG. 4A. The articles are tested
using the same method as described for Example 1. The maximum von
Mises stress is about 600 MPa and is above the yield stress of
foil.
[0160] Example 9 is an article including 7 sealed spaces prepared
using the method of Example 1, except a vacuum of about 200 Torr is
applied when the cover sheet and the base sheet are welded
together. When the thermal energy storage material is at a
temperature of about 25.degree. C., the pressure in the sealed
space is less than about 400 Torr. The articles are tested using
the same method as described for Example 1. The maximum von Mises
stress is less than the yield stress of foil. The primary seal does
not fail during the thermal cycling and the thermal energy storage
material does not leak out of the article after 1,000 thermal
cycles.
[0161] Another article of Example 9 is tested by heating to
400.degree. C. for 20 minutes. At 400.degree. C., the seals fail
and the thermal energy storage material leaks.
[0162] Example 10 is an article including 7 sealed spaces prepared
using the method of Example 1, except the cover sheet and base
sheet are welded together when the thermal energy storage material
is at a temperature of about 250.degree. C. When the thermal energy
storage material is at a temperature of about 25.degree. C., the
pressure in the sealed space is less than about 400 Torr. The
articles are tested using the same method as described for Example
1. The maximum von Mises stress is less than the yield stress of
the foil. The primary seal does not fail during the thermal cycling
and the thermal energy storage material does not leak out of the
article after 1,000 thermal cycles.
[0163] Another article of Example 10 is tested by heating to
400.degree. C. for 20 minutes. At 400.degree. C., the seals fail
and the thermal energy storage material leaks.
[0164] The preferred embodiment of the present invention has been
disclosed. A person of ordinary skill in the art would realize
however, that certain modifications would come within the teachings
of this invention. Therefore, the following claims should be
studied to determine the true scope and content of the
invention.
[0165] Any numerical values recited in the above application
include all values from the lower value to the upper value in
increments of one unit provided that there is a separation of at
least 2 units between any lower value and any higher value. As an
example, if it is stated that the amount of a component or a value
of a process variable such as, for example, temperature, pressure,
time and the like is, for example, from 1 to 90, preferably from 20
to 80, more preferably from 30 to 70, it is intended that values
such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 etc. are expressly
enumerated in this specification. For values which are less than
one, one unit is considered to be 0.0001, 0.001, 0.01 or 0.1 as
appropriate. These are only examples of what is specifically
intended and all possible combinations of numerical values between
the lowest value and the highest value enumerated are to be
considered to be expressly stated in this application in a similar
manner. Unless otherwise stated, all ranges include both endpoints
and all numbers between the endpoints. The use of "about" or
"approximately" in connection with a range applies to both ends of
the range. Thus, "about 20 to 30" is intended to cover "about 20 to
about 30", inclusive of at least the specified endpoints. Parts by
weight as used herein refers to compositions containing 100 parts
by weight. The disclosures of all articles and references,
including patent applications and publications, are incorporated by
reference for all purposes. The term "consisting essentially of" to
describe a combination shall include the elements, ingredients,
components or steps identified, and such other elements
ingredients, components or steps that do not materially affect the
basic and novel characteristics of the combination. The use of the
terms "comprising" or "including" to describe combinations of
elements, ingredients, components or steps herein also contemplates
embodiments that consist essentially of the elements, ingredients,
components or steps. Plural elements, ingredients, components or
steps can be provided by a single integrated element, ingredient,
component or step. Alternatively, a single integrated element,
ingredient, component or step might be divided into separate plural
elements, ingredients, components or steps. The disclosure of "a"
or "one" to describe an element, ingredient, component or step is
not intended to foreclose additional elements, ingredients,
components or steps.
* * * * *