U.S. patent application number 16/064822 was filed with the patent office on 2019-01-03 for electrocaloric heat transfer modular stack.
This patent application is currently assigned to UNITED TECHNOLOGIES CORPORATION. The applicant listed for this patent is UNITED TECHNOLOGIES CORPORATION. Invention is credited to Subramanyaravi Annapragada, Scott Alan Eastman, Joseph V. Mantese, Michael L. Perry, Jonathan Rheaume, Parmesh Verma, Craig R. Walker.
Application Number | 20190003747 16/064822 |
Document ID | / |
Family ID | 55168430 |
Filed Date | 2019-01-03 |
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United States Patent
Application |
20190003747 |
Kind Code |
A1 |
Walker; Craig R. ; et
al. |
January 3, 2019 |
ELECTROCALORIC HEAT TRANSFER MODULAR STACK
Abstract
A heat transfer system is disclosed including a plurality of
modules arranged in a stack. The stack modules include
electrocaloric element and electrodes on each side of the film. A
fluid flow path is disposed between two or more electrocaloric
elements. A first electrical bus element (18) in electrical contact
with the first electrode (14), and a second electrical bus element
(20) in electrical contact with second electrode (16). The first
electrical bus element is electrically connected to at least one
other electrical bus of another electrocaloric element in the stack
at the same polarity as said first electrical bus, or the second
electrical bus element is electrically connected to at least one
other electrical bus of another electrocaloric element in the stack
at the same polarity as said second electrical bus.
Inventors: |
Walker; Craig R.; (South
Glastonbury, CT) ; Rheaume; Jonathan; (West Hartford,
CT) ; Perry; Michael L.; (Glastonbury, CT) ;
Eastman; Scott Alan; (Glastonbury, CT) ; Annapragada;
Subramanyaravi; (Shrewsbury, MA) ; Verma;
Parmesh; (South Windsor, CT) ; Mantese; Joseph
V.; (Ellington, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UNITED TECHNOLOGIES CORPORATION |
Hartford |
CT |
US |
|
|
Assignee: |
UNITED TECHNOLOGIES
CORPORATION
Farmington
CT
|
Family ID: |
55168430 |
Appl. No.: |
16/064822 |
Filed: |
December 21, 2015 |
PCT Filed: |
December 21, 2015 |
PCT NO: |
PCT/US15/67189 |
371 Date: |
June 21, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25B 2321/001 20130101;
F25B 21/00 20130101; Y02B 30/66 20130101; Y02B 30/00 20130101 |
International
Class: |
F25B 21/00 20060101
F25B021/00 |
Claims
1. A heat transfer system, comprising a plurality of modules
arranged in a stack, each of the modules comprising an
electrocaloric element comprising an electrocaloric film, a first
electrode on a first side of the electrocaloric film, and a second
electrode on a second side of the electrocaloric film; a fluid flow
path between two or more electrocaloric elements; a first
electrical bus element in electrical contact with the first
electrode; and a second electrical bus element in electrical
contact with second electrode; wherein the first electrical bus
element is electrically connected to at least one other electrical
bus of another electrocaloric element in the stack at the same
polarity as said first electrical bus, or the second electrical bus
element is electrically connected to at least one other electrical
bus of another electrocaloric element in the stack at the same
polarity as said second electrical bus.
2. The heat transfer system of claim 1, wherein the first
electrical bus element is electrically connected to at least one
other electrical bus of another electrocaloric element in the stack
at the same polarity as said first electrical bus, and the second
electrical bus element is electrically connected to at least one
other electrical bus of another electrocaloric element in the stack
at the same polarity as said second electrical bus.
3. The heat transfer system of claim 1, wherein the first or second
electrical bus is electrically connected to an electrical bus of an
adjacent electrocaloric element in the stack at the same polarity
as said first or second electrical bus.
4. The heat transfer system of claims 1, wherein the first and
second electrical bus elements are each electrically connected to
electrical bus elements of an adjacent electrocaloric element in
the stack at the same polarities as said first and second
electrical bus elements, respectively.
5. The heat transfer system of claim 1, wherein the first
electrical bus element is in an interlocking configuration with an
electrical bus of an adjacent electrocaloric element in the stack,
or the second electrical bus element is in an interlocking
configuration with an electrical bus of an adjacent electrocaloric
element in the stack, or the first electrical bus element and the
second electrical bus element are each in an interlocking
configuration with an electrical bus of an adjacent electrocaloric
element in the stack.
6. (canceled)
7. The heat transfer system of claim 1, wherein the first
electrical bus element is electrically connected to a live
electrode and the second electrical bus element is electrically
connected to a ground electrode.
8. The heat transfer system of claim 1, wherein the first and
second electrical bus elements are disposed along opposite edges of
the electrocaloric element.
9. The heat transfer system of claim 8, wherein the first electrode
extends from the first electrical bus element along the first side
of the electrocaloric film to a position physically separated from
the second electrical bus element, and the second electrode extends
from the second electrical bus element along the second side of the
electrocaloric film to a position physically separated from the
first electrical bus element.
10. The heat transfer system of claim 1, wherein the first and
second electrical bus elements are disposed along a common edge of
the electrocaloric element.
11. The heat transfer system of claim 1, comprising at least two
adjacent electrocaloric elements that share an electrode at least
partially embedded between the electrocaloric films of the adjacent
electrocaloric elements.
12. The heat transfer system of claim 11, wherein the embedded
electrode is a live electrode, and comprising ground electrodes
adjacent to the fluid flow path.
13. The heat transfer system of claim 1, further comprising one or
more spacer elements between electrocaloric elements.
14. The heat transfer system of claim 13, wherein the one or more
spacer elements extend axially along a direction of fluid flow
along the fluid flow path or wherein the one or more
axially-extending spacer elements extend linearly along a direction
of fluid flow along the fluid flow path, or wherein the one or more
axially-extending spacer elements extend non-linearly along a
direction of fluid flow along the fluid flow path.
15. (canceled)
16. (canceled)
17. The heat transfer system of claim 13, wherein the one or more
spacer elements are electrically non-conductive.
18. (canceled)
19. (canceled)
20. The heat transfer system of claim 1, wherein said plurality of
modules further comprise an electrically non-conductive support
member connected to the electrocaloric element.
21. The heat transfer system of claim 20, wherein the support
includes header spaces at opposing ends of the electrocaloric
elements in fluid communication with the fluid flow path.
22. The heat transfer system of claim 20, wherein the supports of
the plurality of modules together form an enclosure within which
the electrocaloric elements and the spacer elements are
disposed.
23. (canceled)
24. (canceled)
25. (canceled)
26. The heat transfer system of claim 1, wherein the first and
second electrodes each comprise a metalized layer deposited on the
electrocaloric film.
27. The heat transfer system of claim 1, further comprising a first
thermal flow path between the fluid flow path and a heat sink a
second thermal flow path between the fluid flow path and a heat
source; and a controller configured to control electrical current
to the electrodes and to selectively direct transfer of heat energy
from the fluid flow path in thermal communication with
electrocaloric element to the heat sink along the first thermal
flow path or from the heat source to the fluid flow path in thermal
communication with the electrocaloric element along the second
thermal flow path.
28. A method of fabricating the heat transfer system claim 1,
comprising assembling repeating units of said modules in a stack
configuration.
Description
BACKGROUND
[0001] A wide variety of technologies exist for cooling
applications, including but not limited to evaporative cooling,
convective cooling, or solid state cooling such as electrothermic
cooling. One of the most prevalent technologies in use for
residential and commercial refrigeration and air conditioning is
the vapor compression refrigerant heat transfer loop. These loops
typically circulate a refrigerant having appropriate thermodynamic
properties through a loop that comprises a compressor, a heat
rejection heat exchanger (i.e., heat exchanger condenser), an
expansion device and a heat absorption heat exchanger (i.e., heat
exchanger evaporator). Vapor compression refrigerant loops
effectively provide cooling and refrigeration in a variety of
settings, and in some situations can be run in reverse as a heat
pump. However, many of the refrigerants can present environmental
hazards such as ozone depleting potential (ODP) or global warming
potential (GWP), or can be toxic or flammable. Additionally, vapor
compression refrigerant loops can be impractical or disadvantageous
in environments lacking a ready source of power sufficient to drive
the mechanical compressor in the refrigerant loop. For example, in
an electric vehicle, the power demand of an air conditioning
compressor can result in a significantly shortened vehicle battery
life or driving range. Similarly, the weight and power requirements
of the compressor can be problematic in various portable cooling
applications.
[0002] Accordingly, there has been interest in developing cooling
technologies as alternatives to vapor compression refrigerant
loops. Various technologies have been proposed such as field-active
heat or electric current-responsive heat transfer systems relying
on materials such as electrocaloric materials, magnetocaloric
materials, or thermoelectric materials. However, many proposals
have been configured as bench-scale demonstrations with limited
capabilities for scalability or mass production.
BRIEF DESCRIPTION
[0003] In some embodiments of this disclosure, a heat transfer
system comprises a plurality of modules arranged in a stack. The
stack modules comprise an electrocaloric element comprising an
electrocaloric film. A first electrode is disposed on a first side
of the electrocaloric film, and a second electrode is disposed on a
second side of the electrocaloric film. A fluid flow path is
disposed between two or more electrocaloric elements. A first
electrical bus element in electrical contact with the first
electrode, and a second electrical bus element in electrical
contact with second electrode. The first electrical bus element is
electrically connected to at least one other electrical bus of
another electrocaloric element in the stack at the same polarity as
said first electrical bus, or the second electrical bus element is
electrically connected to at least one other electrical bus of
another electrocaloric element in the stack at the same polarity as
said second electrical bus.
[0004] The first electrical bus element is electrically connected
to at least one other electrical bus of another electrocaloric
element in the stack at the same polarity as said first electrical
bus, and the second electrical bus element is electrically
connected to at least one other electrical bus of another
electrocaloric element in the stack at the same polarity as said
second electrical bus.
[0005] In any of the foregoing embodiments, the first or second
electrical bus is electrically connected to an electrical bus of an
adjacent electrocaloric element in the stack at the same polarity
as said first or second electrical bus.
[0006] In any of the foregoing embodiments, the first and second
electrical bus elements are each electrically connected to
electrical bus elements of an adjacent electrocaloric element in
the stack at the same polarities as said first and second
electrical bus elements, respectively.
[0007] In any of the foregoing embodiments, the first or second
electrical bus element is in an interlocking configuration with an
electrical bus of an adjacent electrocaloric element in the
stack.
[0008] In any of the foregoing embodiments, the first and second
electrical bus elements are each in an interlocking configuration
to electrical bus elements of an adjacent electrocaloric element in
the stack.
[0009] In any of the foregoing embodiments, the first electrical
bus element is electrically connected to a live electrode and the
second electrical bus element is electrically connected to a ground
electrode.
[0010] In any of the foregoing embodiments, the first and second
electrical bus elements are disposed along opposite edges of the
electrocaloric element.
[0011] In any of the foregoing embodiments, the first electrode
extends from the first electrical bus element along the first side
of the electrocaloric film to a position physically separated from
the second electrical bus element, and the second electrode extends
from the second electrical bus element along the second side of the
electrocaloric film to a position physically separated from the
first electrical bus element.
[0012] In any of the foregoing embodiments, the first and second
electrical bus elements are disposed along a common edge of the
electrocaloric element.
[0013] In any of the foregoing embodiments, at least two adjacent
electrocaloric elements that share an electrode are at least
partially embedded between the electrocaloric films of the adjacent
electrocaloric elements.
[0014] In any of the foregoing embodiments, the embedded electrode
is a live electrode, and comprising ground electrodes adjacent to
the fluid flow path.
[0015] In any of the foregoing embodiments, one or more spacer
elements are disposed between electrocaloric elements.
[0016] In any of the foregoing embodiments, the one or more spacer
elements extend axially along a direction of fluid flow along the
fluid flow path.
[0017] In any of the foregoing embodiments, the one or more
axially-extending spacer elements extend linearly along a direction
of fluid flow along the fluid flow path.
[0018] In any of the foregoing embodiments, the one or more
axially-extending spacer elements extend non-linearly along a
direction of fluid flow along the fluid flow path.
[0019] In any of the foregoing embodiments, the one or more spacer
elements are electrically non-conductive.
[0020] In any of the foregoing embodiments, the electrocaloric
element thickness is 1 .mu.m to 1000 .mu.m.
[0021] In any of the foregoing embodiments, the physical separation
between electrocaloric elements in adjacent modules is from 1 .mu.m
to 200 mm.
[0022] In any of the foregoing embodiments, the plurality of
modules further comprise an electrically non-conductive support
member connected to the electrocaloric element.
[0023] In any of the foregoing embodiments, the support includes
header spaces at opposing ends of the electrocaloric elements in
fluid communication with the fluid flow path.
[0024] In any of the foregoing embodiments, the supports of the
plurality of modules together form an enclosure within which the
electrocaloric elements and the spacer elements are disposed.
[0025] In any of the foregoing embodiments, the electrocaloric film
comprises an electrocaloric polymer.
[0026] In any of the foregoing embodiments, the electrocaloric
polymer comprises polyvinylidene fluoride (PVDF) or a liquid
crystal polymer (LCP),
[0027] In any of the foregoing embodiments, the electrocaloric film
comprises an inorganic electrocaloric material.
[0028] In any of the foregoing embodiments, the first and second
electrodes each comprise a metalized layer deposited on the
electrocaloric film.
[0029] In some embodiments, a heat transfer system comprises an
electrocaloric element formed by the method of any of the above
embodiments, a first thermal flow path between the electrocaloric
element and a heat sink, a second thermal flow path between the
electrocaloric element and a heat source, and a controller
configured to control electrical current to the conductive layers
and to selectively direct transfer of heat energy from the
electrocaloric element to the heat sink along the first thermal
flow path or from the heat source to the electrocaloric element
along the second thermal flow path.
[0030] In another aspect, a method of fabricating the heat transfer
system of any of the foregoing embodiments comprises assembling
repeating units of the modules in a stack configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Subject matter of this disclosure is particularly pointed
out and distinctly claimed in the claims at the conclusion of the
specification. The foregoing and other features, and advantages of
the present disclosure are apparent from the following detailed
description taken in conjunction with the accompanying drawings in
which:
[0032] FIG. 1 is a schematic depiction of a top view of an example
embodiment of an electrocaloric heat transfer module;
[0033] FIG. 2 is a schematic depiction of a cross-section side view
of an example embodiment of an electrocaloric heat transfer
module;
[0034] FIG. 3A is a schematic depiction of an exploded perspective
view of an electrode and electrocaloric film configuration;
[0035] FIG. 3B is a top view of a portion of the configuration of
FIG. 4 with an electric bus element:
[0036] FIG. 4 is a schematic depiction of an example embodiment of
a stack assembly of a number of electrocaloric heat transfer
modules;
[0037] FIG. 5 is a schematic depiction of an alternate example
embodiment of a stack assembly of a number of electrocaloric heat
transfer modules and
[0038] FIG. 6 is a schematic depiction of an example embodiment of
heat transfer system comprising an electrocaloric stack and other
components.
DETAILED DESCRIPTION
[0039] As mentioned above, a heat transfer system is disclosed that
comprises a plurality of modules arranged in a stack. An example of
an embodiment of a module is schematically depicted in FIGS. 1 and
2. Although any directions described herein (e.g., "up", "down",
"top", "bottom", "left", "right", "over", "under", etc.) are
considered to be arbitrary and to not have any absolute meaning but
only a meaning relative to other directions, FIG. 1 can be
described as a "top" view of an example embodiment of a module and
FIG. 2 can be described as a "side" cross-section view taken along
the line A4A shown in FIG. 1. As shown in FIGS. 1 and 2, a module
10 comprises an electrocaloric element comprises an electrocaloric
film 12, a first electrode 14 on a first side of the film and a
second electrode 16 on a second side of the film. It is noted that,
for ease of illustration so that details of the electrocaloric film
12 and other components are not obscured, the electrodes 14, 16 are
omitted from FIG. 1 and are only illustrated in FIG. 2.
[0040] The electrocaloric film 12 can comprise any of a number of
electrocaloric materials. In some embodiments, electrocaloric film
thickness can be in a range from having a lower limit of 0.1 .mu.m,
more specifically 0.5 .mu.m, and even more specifically 1 .mu.m. In
some embodiments, the film thickness range can and having an upper
limit of 1000 .mu.m, more specifically 100 .mu.m, and even more
specifically 10 .mu.m. It is understood that these upper and lower
range limits can be independently combined to disclose a number of
different possible ranges. Examples of electrocaloric materials for
the electrocaloric film can include but are not limited to
inorganic materials (e.g., ceramics), electrocaloric polymers, and
polymer/ceramic composites. Examples of inorganics include but are
not limited to PbTiO.sub.3 ("PT"), Pb(Mg.sub.1/3Nb.sub.2/3)O.sub.3
("PMN"), PMN-PT, LiTaO.sub.3, barium strontium titanate (BST) or
PZT (lead, zirconium, titanium, oxygen). Examples of electrocaloric
polymers include, but are not limited to ferroelectric polymers,
liquid crystal polymers, and liquid crystal elastomers.
[0041] Ferroelectric polymers are crystalline polymers, or polymers
with a high degree of crystallinity, where the crystalline
alignment of polymer chains into lamellae and/or spherulite
structures can be modified by application of an electric field.
Such characteristics can be provided by polar structures integrated
into the polymer backbone or appended to the polymer backbone with
a fixed orientation to the backbone. Examples of ferroelectric
polymers include polyvinylidene fluoride (PVDF), polytriethylene
fluoride, odd-numbered nylon, copolymers containing repeat units
derived from vinylidene fluoride, and copolymers containing repeat
units derived from triethylene fluoride. Polyvinylidene fluoride
and copolymers containing repeat units derived from vinylidene
fluoride have been widely studied for their ferroelectric and
electrocaloric properties. Examples of vinylidene
fluoride-containing copolymers include copolymers with methyl
methacrylate, and copolymers with one or more halogenated
co-monomers including but not limited to trifluoroethylene,
tetrafluoroethylene, chlorotrifluoroethylene, trichloroethylene,
vinylidene chloride, vinyl chloride, and other halogenated
unsaturated monomers.
[0042] Liquid crystal polymers, or polymer liquid crystals comprise
polymer molecules that include mesogenic groups. Mesogenic
molecular structures are well-known, and are often described as
rod-like or disk-like molecular structures having electron density
orientations that produce a dipole moment in response to an
external field such as an external electric field. Liquid crystal
polymers typically comprise numerous mesogenic groups connected by
non-mesogenic molecular structures. The non-mesogenic connecting
structures and their connection, placement and spacing in the
polymer molecule along with mesogenic structures are important in
providing the fluid deformable response to the external field.
Typically, the connecting structures provide stiffness low enough
so that molecular realignment is induced by application of the
external field, and high enough to provide the characteristics of a
polymer when the external field is not applied.
[0043] In some exemplary embodiments, a liquid crystal polymer can
have rod-like mesogenic structures in the polymer backbone
separated by non-mesogenic spacer groups having flexibility to
allow for re-ordering of the mesogenic groups in response to an
external field. Such polymers are also known as main-chain liquid
crystal polymers. In some exemplary embodiments, a liquid crystal
polymer can have rod-like mesogenic structures attached as side
groups attached to the polymer backbone. Such polymers are also
known as side-chain liquid crystal polymers.
[0044] With continued reference to FIGS. 1 and 2, first electrode
14 is electrically connected to a first electrical bus element 18.
Similarly, second electrode 16 is electrically connected to second
electrical bus element 20. The electrodes can be any type of
conductive material, including but not limited to metallized layers
of a conductive metal such as aluminum or copper, or other
conductive materials such as carbon (e.g., carbon nanotubes,
graphene, or other conductive carbon). Noble metals can also be
used, but are not required. Other conductive materials such as a
doped semiconductor, ceramic, or polymer, or conductive polymers
can also be used. In some embodiments, the electrical bus elements
18 and 20 of opposite polarity are disposed on opposite edges of
the electrocaloric film 12 as shown in FIG. 2, which can in some
embodiments provide a physical separation that can reduce the risk
of short circuits. As also shown in FIG. 2, the electrodes 14 and
16 can extend from a position in contact with an electrical bus
element on one edge of the film and extend across the film to a
position that is not in contact with the electrical bus element of
opposite polarity on the other edge of the film 12. In some
embodiments, the electrical bus elements 18 and 20 can be disposed
on the same side of the electrocaloric element as shown in FIGS. 3A
and 3B. FIG. 3A is a schematic depiction of a perspective exploded
view of an electrocaloric film 12 having a top electrode 14 and a
bottom electrode 16. The top and bottom electrodes in FIGS. 3A and
3B have lead portions 14y and 16y for an electrical connection to
an electrical bus element 19. The connection between the electrodes
14, 16 and the bus element 19 is depicted in a top view in FIG. 3B
where only a portion of electrocaloric film 12 and the bus element
19 are shown. As shown in FIG. 3B, bus element has a first polarity
portion 19a connected to the lead portion 14y of top electrode 14
and a second polarity portion 19b connected to the lead portion 16y
of bottom electrode 16, and an electrically non-conductive portion
19c that electrically isolates the portions 19a and 19b of
different polarities.
[0045] One or more support elements 22 can optionally be included
for support and retention of the electrocaloric element. However,
separate support elements are not required, as support and
retention can also be provided by the bus elements as shown in FIG.
4 described below. As shown in FIG. 1, the support element(s) 22
can be configured to provide header spaces 24 and 26 for transport
of working fluids to and from the electrocaloric element along
fluid flow path 25. Although not required in all design
configurations, in some embodiments, the support elements can be
made from an electrically non-conductive material.
[0046] Spacer elements 28 can optionally be included to help
maintain separation from adjacent electrocaloric elements for a
fluid flow path for a working fluid (e.g., either a fluid to be
heated or cooled directly such as air, or a heat transfer fluid
such as a dielectric organic compound). Any configuration of spacer
elements can be utilized, such as a set of discrete disk spacer
elements. In some aspects, however, the spacer elements extend
axially in a direction parallel to the direction of the fluid flow
path 25. Such axial extension can be linear (i.e., in a straight
line) as shown in FIG. 1, or can be non-linear (e.g., in a zig-zag
or wavy pattern that extends generally in an axial direction. In
some embodiments, the non-linearity can promote good fluid mixing
while the general extension in the axial direction can help avoid
excessive back-pressure to the flowing fluid.
[0047] Turning now to FIG. 4 where like numbering is used as FIGS.
1 and 2, a number of modules 10 are shown assembled together in a
stack 30. As can be seen in FIG. 3, the spacers promote maintaining
a physical separation between adjacent electrocaloric elements to
provide a fluid flow path 25 between the spacers and the adjacent
electrocaloric elements. Although not required in all design
configurations, in design configurations where the spacer elements
are disposed adjacent to electrodes of opposite polarity as shown
in FIG. 3, the spacer elements can be made from an electrically
non-conductive material. In some embodiments, spacing between
adjacent electrocaloric elements can be in a range from having a
lower limit of 1 .mu.m, more specifically 10 .mu.m, and even more
specifically 50 .mu.m. In some embodiments, the separation spacing
range can have an upper limit of 200 mm, more specifically 10 mm,
even more specifically 2 mm. It is understood that these upper and
lower range limits can be independently combined to disclose a
number of different possible ranges.
[0048] In some embodiments, adjacent electrical bus elements 18, 20
can have an interlocking configuration as shown in FIG. 4. As used
herein, interlocking means that adjacent elements have
complementary contour of projections and recesses where a
projection of one bus element projects is adjacent or projects into
to a complementary recess of an adjacent bus element. Such an
arrangement can in some embodiments facilitate assembly and promote
structural integrity and electrical continuity of the assembled bus
elements in the stack.
[0049] FIG. 4 depicts a stack with alternating electrocaloric
elements and fluid flow passages; however, FIG. 4 represents only
one example of a stack embodiment and is not limiting. An alternate
embodiment is depicted in FIG. 5. With reference now to FIG. 5, a
stack 30a is shown where bus elements 18b are connected to a bus
bar 18a and bus elements 20b are connected to a bus bar 20a. As
shown in FIG. 5 the electrodes 16a electrically connected to bus
elements 20b are at least partially embedded between the
electrocaloric films 12 of adjacent electrocaloric elements. In
this embodiment, the electrode 16a serves as an electrode for two
adjacent electrocaloric elements or, put another way, the two
adjacent electrocaloric elements share a single electrode. The
electrodes 14a of opposite polarity are disposed on the outside of
the electrocaloric element `sandwich` and are not shared. This
configuration can provide technical benefits by protecting the
embedded electrode 16a from potential short circuits. In some
embodiments, the at least partially embedded electrode is a live
electrode, and the electrode exposed to the fluid flow path 25 is a
ground electrode. It should be noted that although FIG. 5 depicts a
sandwich of two films surrounding the embedded electrode,
sandwiches of more than two films with embedded electrodes of
alternating polarities are also contemplated.
[0050] An example embodiment of a heat transfer system and its
operation are further described with respect to FIG. 6. As shown in
FIG. 6, a heat transfer system 310 comprises an electrocaloric
stack 311 has one or more electrically conductive liquids in
thermal communication with a heat sink 317 through a first thermal
flow path 318, and in thermal communication with a heat source 320
through a second thermal flow path 322. A controller 324 is
configured to control electrical current to through a power source
(not shown) to selectively activate electrocaloric elements (not
shown) in the stack 311. The controller 324 is also configured to
open and close control valves 326 and 328 to selectively direct the
electrically conductive liquid along the first and second flow
paths 318 and 322.
[0051] In operation, the system 310 can be operated by the
controller 324 applying an electric field as a voltage differential
across the electrocaloric elements in the stack 311 to cause a
decrease in entropy and a release of heat energy by the
electrocaloric elements. The controller 324 opens the control valve
326 to transfer at least a portion of the released heat energy
along flow path 318 to heat sink 317. This transfer of heat can
occur after the temperature of the electrocaloric elements has
risen to a threshold temperature. In some embodiments, heat
transfer to the heat sink 317 is begun as soon as the temperature
of the electrocaloric elements increases to be about equal to the
temperature of the heat sink 317. After application of the electric
field for a time to induce a desired release and transfer of heat
energy from the electrocaloric elements to the heat sink 317, the
electric field can be removed. Removal of the electric field causes
an increase in entropy and a decrease in heat energy of the
electrocaloric elements. This decrease in heat energy manifests as
a reduction in temperature of the electrocaloric elements to a
temperature below that of the heat source 320. The controller 324
closes control valve 326 to terminate flow along flow path 318, and
opens control device 328 to transfer heat energy from the heat
source 320 to the colder electrocaloric elements.
[0052] In some embodiments, for example where a heat transfer
system is utilized to maintain a temperature in a conditioned space
or thermal target, the electric field can be applied to the
electrocaloric elements to increase its temperature until the
temperature of the electrocaloric element reaches a first
threshold. After the first temperature threshold, the controller
324 opens control valve 326 to transfer heat from the
electrocaloric elements to the heat sink 317 until a second
temperature threshold is reached. The electric field can continue
to be applied during all or a portion of the time period between
the first and second temperature thresholds, and is then removed to
reduce the temperature of the electrocaloric elements until a third
temperature threshold is reached. The controller 324 then closes
control valve 326 to terminate heat flow transfer along heat flow
path 318, and opens control valve 328 to transfer heat from the
heat source 320 to the electrocaloric elements. The above steps can
be optionally repeated until a target temperature of the
conditioned space or thermal target (which can be either the heat
source or the heat sink) is reached.
[0053] While the present disclosure has been described in detail in
connection with only a limited number of embodiments, it should be
readily understood that the present disclosure is not limited to
such disclosed embodiments. Rather, the present disclosure can be
modified to incorporate any number of variations, alterations,
substitutions or equivalent arrangements not heretofore described,
but which are commensurate with the spirit and scope of the present
disclosure. Additionally, while various embodiments of the present
disclosure have been described, it is to be understood that aspects
of the present disclosure may include only some of the described
embodiments. Accordingly, the present disclosure is not to be seen
as limited by the foregoing description, but is only limited by the
scope of the appended claims.
* * * * *