U.S. patent application number 15/532242 was filed with the patent office on 2017-09-21 for field-active heat pumping using liquid materials.
The applicant listed for this patent is UNITED TECHNOLOGIES CORPORATION. Invention is credited to Subramanyaravi Annapragada, Michael J. Birnkrant, Andrzej Ernest Kuczek, Joseph V. Mantese, Matthew Robert Pearson, Thomas D. Radcliff, Ram Ranjan, Parmesh Verma.
Application Number | 20170268805 15/532242 |
Document ID | / |
Family ID | 52134436 |
Filed Date | 2017-09-21 |
United States Patent
Application |
20170268805 |
Kind Code |
A1 |
Radcliff; Thomas D. ; et
al. |
September 21, 2017 |
FIELD-ACTIVE HEAT PUMPING USING LIQUID MATERIALS
Abstract
Heat pump cycle provided with a fluidic loop connecting two heat
exchangers. The fluidic loop is filled with an electro-caloric
liquid as a heat transfer medium. Applying electric filed in one of
the heat exchangers the temperature of the electro-caloric liquid
is changed.
Inventors: |
Radcliff; Thomas D.;
(Vernon, CT) ; Mantese; Joseph V.; (Ellington,
CT) ; Annapragada; Subramanyaravi; (Shrewsbury,
MA) ; Birnkrant; Michael J.; (Kenilworth, NJ)
; Kuczek; Andrzej Ernest; (Bristol, CT) ; Ranjan;
Ram; (Glastonbury, CT) ; Verma; Parmesh;
(South Windsor, CT) ; Pearson; Matthew Robert;
(East Hartford, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UNITED TECHNOLOGIES CORPORATION |
Farmington |
CT |
US |
|
|
Family ID: |
52134436 |
Appl. No.: |
15/532242 |
Filed: |
December 4, 2014 |
PCT Filed: |
December 4, 2014 |
PCT NO: |
PCT/US2014/068497 |
371 Date: |
June 1, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02B 30/00 20130101;
Y02B 30/66 20130101; F25B 21/00 20130101; F25B 2321/001 20130101;
Y02B 30/52 20130101 |
International
Class: |
F25B 21/00 20060101
F25B021/00 |
Claims
1. A heat pump cycle for heat exchange, comprising: providing a
fluidic loop between two heat exchangers in fluidic communication
with each other; energizing at least a first heat exchanger of the
two heat exchangers to generate an electric field in the first heat
exchanger; advecting a field-active liquid through the fluidic
loop; changing an entropy of the field-active liquid in response to
advecting into the electric field of the at least first heat
exchanger; and exchanging heat between the field-active liquid and
the two heat exchangers in response to the changing of the entropy
of the field-active liquid.
2. The heat pump cycle of claim 1, further comprising imposing an
electric field in the first and the second heat exchangers.
3. The heat pump cycle of claim 1, further comprising at least one
of rejecting or absorbing heat in the field-active liquid in
response to the advecting of the field active liquid through the at
least first heat exchanger.
4. The heat pump cycle of claim 1, further comprising: providing
liquid-gas heat exchangers or liquid-liquid heat exchangers in a
counter flow or cross-counter flow configuration; and applying the
electric field to one fluid stream of the liquid-gas heat
exchangers or the liquid-liquid heat exchangers.
5. The heat pump cycle of claim 1, further comprising using an
active electrocaloric liquid as the field-active liquid that is
selected from one of a single component field-active liquid, a
multi-component mixture of field-active liquids, a pumpable
multi-component mixture including field-active liquid and
field-active solid materials, or an inactive dielectric liquid
added to a solid field-active material to enable pumping of the
solid material field-active material.
6. The heat pump cycle of claim 5, further comprising using a
liquid crystal as the field-active liquid.
7. The heat pump cycle of claim 1, further comprising energizing
the at least first heat exchanger to continuously generate the
electric field.
8. The heat pump cycle of claim 1, further comprising energizing
the field-active liquid to change entropy of the field-active
liquid.
9. The heat pump cycle of claim 1 wherein at least the first heat
exchanger of the two heat exchangers comprises two electrically
conductive channels separated by an insulating material to define a
flow channel for the field-active liquid between the two
electrically conductive channels.
10. The heat pump cycle of claim 1 wherein at least the first heat
exchanger of the two heat exchangers comprises a polymer channel
defining a flow channel for the field-active liquid, the polymer
channel including a first electrode on one side and a second
electrode on another side to generate the electric field.
11. The heat pump cycle of claim 1, further comprising: providing a
second fluidic loop between two additional heat exchangers in
fluidic communication with each other; placing the energized first
heat exchanger in a heat exchanger relationship with a deenergized
heat exchanger of the second fluidic loop.
12. The heat pump cycle of claim 11, further comprising: energizing
at least a first heat exchanger of the two additional heat
exchangers.
13. The heat pump cycle of claim 12, further comprising: providing
a third fluidic loop between two further heat exchangers in fluidic
communication with each other; placing the energized first heat
exchanger of the two additional heat exchangers in a heat exchanger
relationship with a deenergized heat exchanger of the third fluidic
loop.
14. The heat pump cycle of claim 13, wherein placing the energized
first heat exchanger in a heat exchanger relationship with a
deenergized heat exchanger of the second fluidic loop comprises
physically stacking the energized first heat exchanger and the
deenergized heat exchanger of the second fluidic loop.
15. A regenerative field-active heat pump cycle for heat transport
having a regenerator and secondary heat exchanger elements,
comprising: energizing the regenerator and a first heat exchanger
of the secondary heat exchanger elements to apply an intermittent
electric field; changing an entropy of the field-active liquid
resident in the regenerator and a first heat exchanger of the
secondary heat exchanger elements in response to the electric
field; advecting the field-active liquid from the regenerator into
the first heat exchanger of the secondary heat exchanger elements
while maintaining the electric field; transferring heat from the
first heat exchanger to a hot ambient temperature in response to
advecting the hot energized field-active liquid into the heat
exchanger; releasing the field in the regenerator and a first heat
exchanger of the secondary heat exchanger elements; changing an
entropy of the field-active liquid resident in the regenerator and
a first heat exchanger of the secondary heat exchanger elements in
response to releasing the electric field; advecting the cold
field-active liquid from the regenerator into the second heat
exchanger of the secondary heat exchanger elements while
maintaining the electric field; and transferring heat from the
second heat exchanger to a cold ambient temperature in response to
advecting the cold de-energized field-active liquid into the heat
exchanger.
16. The regenerative field-active heat pump cycle of claim 15,
further comprising advecting the field-active liquid through the
regenerator and the secondary heat exchanger elements by pumping
using a linear actuator, a mechanical pump, an electrophoretic
electric field pump, or an electrostatic electric field pump.
17. The regenerative field-active heat pump cycle of claim 15,
wherein the field-active liquid is static in the regenerator and a
secondary fluid is advected through the regenerator and the
secondary heat exchanger elements.
18. The regenerative field-active heat pump cycle of claim 17,
further comprising transferring heat from the field-active liquid
and the secondary fluid in the regenerator.
19. The regenerative field-active heat pump cycle of claim 15,
further comprising providing the regenerator with an active solid
electrocaloric material.
20. The regenerative field-active heat pump cycle of claim 19,
further comprising energizing the regenerator active solid
structure and the field-active liquid with the same electrodes.
21. The regenerative field-active heat pump cycle of claim 15,
further comprising providing the regenerator and at least the first
of the secondary heat exchanger elements with an active solid
electrocaloric material.
22. The regenerative field-active heat pump cycle of claim 21,
further comprising energizing the at least first heat exchanger,
the regenerator, and the field-active liquid with the same
electrodes simultaneously or in sequence.
23. The regenerative field-active heat pump cycle of claim 15,
further comprising: providing at least one of the regenerator and
the secondary heat exchanger elements from magnetocaloric
materials, elastocaloric materials, or optocaloric materials; and
applying an electric field to the field-active liquid while
energizing at least one of the regenerator and the secondary heat
exchanger elements with an applied magnetic, strain, or light
field, respectively in an advantageous phase relationship.
Description
FIELD OF THE INVENTION
[0001] The subject matter disclosed herein relates generally to the
field of electrocaloric materials and, more particularly, to a heat
pump system that uses liquid-phase electrocaloric materials.
BACKGROUND OF THE INVENTION
[0002] Typical heating, ventilation, and air conditioning
functionality ("HVAC") is provided by vapor compression, or reverse
Rankine, cycles. These devices use two-phase fluorinated
refrigerants which are under high pressure and exhibit significant
global warming potential when they inevitably leak into the
atmosphere. Also, the compression process cannot be efficiently
scaled to small sizes restricting energy savings achievable through
distributed heat pumping. Finally, such compressors tend to be
noisy. A scalable, quiet, and environmentally friendly alternative
is desired.
[0003] Materials that exhibit adiabatic temperature change when
subject to mechanical strain, magnetic fields, or electrical fields
have been used to create heat pump cycles. For example,
field-active materials can include electrocaloric and
magnetocaloric materials. Electrocaloric materials exhibit large
entropy changes when an electric field is applied to their
structure. A basic heat pump cycle that implements an
electrocaloric material is shown in FIG. 1. At state 1, a material
is at steady temperature and is subject to a steady field applied
directly to the material. An increase in the applied field strength
increases material temperature at state 2. Heat is rejected to a
hot ambient bringing the material temperature down near the hot
ambient value in state 3. This is best accomplished through direct
contact of the ambient air and the active material. Reduction of
the field strength reduces material temperature at state 4. The
cycle is then completed by absorbing heat from a cold ambient,
again preferably through direct contact, causing the material
temperature to rise back to the temperature value at state 1. This
cycle may approximate ideal Carnot, Brayton, or Ericsson cycles
depending on the timing of field actuation in relation to heat
rejection.
[0004] The adiabatic temperature lift available with known
elcctrocaloric or magnetocaloric materials is typically lower than
the lift required for most commercial heat pump applications such
as environmental control. One well-known means of increasing
temperature lift (at the expense of capacity) is thermal
regeneration. A typical regenerative heat exchanger depends on
thermal storage and reciprocating fluid motion to develop an axial
temperature gradient and thus multiply temperature lift.
Regenerative heat exchangers are common in cycles that use fluid
compression rather than field-active materials to provide heat
pumping. For example, Stirling cycle coolers, and thermoacoustic
coolers that apply a modified Stirling cycle, use regenerative heat
exchangers as common practice. In these regenerative heat
exchangers, the work for heat pumping comes from
compression/expansion of the fluid within the regenerator and the
solid material of the regenerator provides the heat capacity for
regeneration. Also, in a thermoacoustic or other pressure-based
regenerative cooling cycle, it is necessary to use a heat exchanger
to separate the pressurized working fluid from the ambient air
resulting in a significant loss in performance. Regenerative heat
exchanger use has also been reported in field-active magnetocaloric
cooler prototypes.
BRIEF SUMMARY OF THE INVENTION
[0005] In accordance with an embodiment, a heat pump cycle includes
providing a fluidic loop between two heat exchangers in fluidic
communication with each other; energizing at least a first heat
exchanger of the two heat exchangers to generate an electric field
in the first heat exchanger, advecting a field-active liquid
through the fluidic loop; changing an entropy of the field-active
liquid in response to advecting into the electric field of the at
least first heat exchanger; and exchanging heat between the
field-active liquid and the two heat exchangers in response to the
changing of the entropy of the field-active liquid.
[0006] In accordance with another embodiment a regenerative
field-active heat pump cycle for heat transport having a
regenerator and secondary heat exchanger elements includes
energizing the regenerator and a first heat exchanger of the
secondary heat exchanger elements to apply an intermittent electric
field; changing an entropy of the field-active liquid resident in
the regenerator and a first heat exchanger of the secondary heat
exchanger elements in response to the electric field; advecting the
field-active liquid from the regenerator into the first heat
exchanger of the secondary heat exchanger elements while
maintaining the electric field; transferring heat from the first
heat exchanger to a hot ambient temperature in response to
advecting the hot energized field-active liquid into the heat
exchanger; releasing the field in the regenerator and a first heat
exchanger of the secondary heat exchanger elements; changing an
entropy of the field-active liquid resident in the regenerator and
a first heat exchanger of the secondary heat exchanger elements in
response to releasing the electric field; advecting the cold
field-active liquid from the regenerator into the second heat
exchanger of the secondary heat exchanger elements while
maintaining the electric field; and transferring heat from the
second heat exchanger to a cold ambient temperature in response to
advecting the cold do-energized field-active liquid into the heat
exchanger.
[0007] Technical function of the one or more claims described above
provides heat transfer through a field-active liquid that heats or
cools upon application of a field, and heat transfer occurs in a
heat exchanger with the associated hot or cool environment until
the liquid comes into near-equilibrium with the environs while
remaining in the field.
[0008] Other aspects, features, and techniques of the invention
will become more apparent from the following description taken in
conjunction with the drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0009] The subject matter, which is regarded as the invention, 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 invention are apparent from the
following detailed description taken in conjunction with the
accompanying drawings in which like elements are numbered alike in
the several FIGURES:
[0010] FIG. 1 is a diagram of a field-activated heat pump cycle in
accordance with the prior art;
[0011] FIG. 2 is an exemplary system diagram for a heat pump cycle
that utilizes a field-active liquid in accordance with an
embodiment of the invention;
[0012] FIG. 3A is a general perspective view of an exemplary heat
exchanger that has multiple flow tubes and electrodes in accordance
with an embodiment of the invention;
[0013] FIG. 3B is a side elevation view of an exemplary heat
exchanger of FIG. 3A that has multiple flow tubes and electrodes in
accordance with an embodiment of the invention;
[0014] FIG. 4 is a front elevation view of an exemplary regenerator
in accordance with an embodiment of the invention;
[0015] FIG. 5 illustrates an exemplary hybridized regenerator
system for use in accordance with embodiments of the invention;
and
[0016] FIGS. 6A-6C illustrates a cascade regenerator system that
integrates multiple electrocaloric loops in accordance with an
embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Embodiments of the invention described below include using
liquid-based electrocaloric materials as the working fluids for
heat pumping in heating, ventilation, and air conditioning ("HVAC")
and refrigeration systems, as well as in hybrid systems containing
field-active liquid and solid materials. In embodiments, the
field-active liquid is circulated through at least two heat
exchanger elements, wherein a heat transfer process occurs in the
presence of an electric field in one and in the absence of field in
the other. The field causes the field-active liquid to either heat
or cool (depending on the specific liquid composition), and heat
transfer occurs in the heat exchanger with the associated hot or
cool environment until the liquid comes into near-equilibrium with
the environs while remaining in the field. As the liquid leaves the
field it cools or heats (respectively) and the fluid enters a
de-energized heat exchanger to once again transfer heat to the
cool/hot environment.
[0018] Referring to FIG. 2, a basic system 200 for a heat pump
cycle is illustrated in accordance with an embodiment of the
invention. System 200 includes a plurality of heat exchangers 202
and 204 that are in fluidic communication with each other through a
flow tube or passage 206. Heat exchanger 202 includes electrodes
212 and 214 in order to generate an electric field in the heat
exchanger. Flow tube 206 contains a field-active liquid material
that is circulated between heat exchangers 202 and 204 and through
the flow tube 206 continuously. In an embodiment, flow tube 206
includes insulation 210 in order to prevent heat exchange between
the field-active liquid material and an external environment. A
pump 208 creates the pressure to advect or pump the field-active
liquid material through the flow tube 206 and the heat exchangers
202 and 204. In some non-limiting examples, pump 206 can be a
mechanical pump, an electrostatic electric field pump, an
electrophoretic electric field pump, or the like. Also, the
field-active liquid material exhibits temperature change when
subject to the electrical field in heat exchanger 202 and can be an
liquid electrocaloric material. Non-limiting examples of liquid
electrocaloric materials can include liquid crystals, ionic
liquids, or other similar liquids that can exhibit a temperature
change in an electric field. It is to be appreciated that the
field-active liquid material serves as the working fluid for the
heat pumping cycle as well as enabling heat exchange between heat
exchangers 202 and 204 and an external environment 216.
[0019] Field-active materials including liquid crystals respond to
an applied electric field, creating internal order/disorder; and
therefore are capable of storing or releasing energy in the form of
caloric heat and electrical capacitive energy. The field-active
material can alter its order parameter with the applied electric
field. As the order parameter is directly related to the system
entropy and free energy, cooling and heating are consequences of
electric field release or application, or of advection of the
field-active material through a localized continuous electric
field.
[0020] In an exemplary operation for system 200, the field-active
liquid material is circulated through heat exchanger elements 202
and 204, wherein an electric field is applied or not applied during
a heat transfer process. Field-active liquid material is pumped
into heat exchanger 202 where an electric field is applied. The
electric field causes the field-active liquid material to transfer
heat to the associated hot environment 218 (e.g., outdoors in
cooling mode or indoors in heating mode) until the field-active
liquid material comes into near-equilibrium with the environs while
remaining in the electric field. As the field-active liquid
material leaves the electric field it cools and the field-active
liquid material enters a de-energized heat exchanger 204 to absorb
heat from cold environment 216 (e.g., indoors in cooling mode or
outdoors in heating mode). This cycle is repeated continuously. It
is to be appreciated that, for maximizing performance of system
200, the field-active liquid material is energized in the same
location that heat exchange occurs as any interruption of electric
field will return the field-active liquid material to its original
temperature. So, a heat exchanger integrated with electrodes that
can apply the required uniform field can be used, for example, as
heat exchanger 202.
[0021] FIG. 3A illustrates an exemplary heat exchanger that can be
used with system 200 of FIG. 2 to provide an effective cooling
device. Preferably, in embodiments, a multiple channel liquid-air
heat exchanger with a counter flow configuration or a cross-counter
flow configuration can be used, but other configurations of heat
exchangers can also be used in accordance with embodiments of the
invention. In other embodiments, liquid-gas heat exchangers or
liquid-liquid heat exchangers in a counter flow or cross-counter
flow configuration can also be used. An exemplary counter flow heat
exchanger 300 is illustrated in FIG. 3A. Heat exchanger 300 is a
tube-fin structure heat exchanger and includes a plurality of
electrically conductive channels that serve as tubes or conduits
302 for a secondary heat exchange fluid. In one embodiment, this
fluid is a liquid such as water or oil. In another embodiment, this
fluid is air. Each fluid-containing tube 302 is separated by an
insulating material 306 such that each tube 302 and its associated
fins, if any, can be energized independently. The space 304 between
any two tubes 302 contains field-active liquid material wherein a
field can be applied to this liquid by applying a potential to the
surrounding conductive tubes 302 without applying any field to the
secondary heat transfer fluid. Each tube-fin structure of heat
exchanger 300 serves as an electrode and will be energized with
potential of opposing polarity. The liquid heat exchanger 300 can
be made out of metal tubes but other materials could also be used
given the low pressure of the process. Polymer or ceramic-walled
heat exchangers with deposited electrodes can also be used. As
shown in FIG. 3B, positive electrodes 310a-310c and negative
electrodes 312a-312c are placed with opposing polarity to create an
electrical field in the flowing field-active liquid material, but
are placed with similar polarity surrounding the secondary fluid to
avoid any electrical discharge through this fluid. In embodiments,
the walls of the heat exchanger could be made of a solid
field-active ceramic or polymer such as PZT ceramic or PVDF
polymer. One set of electrodes can now energize both active liquid
and active solid material simultaneously, increasing the specific
capacity of the overall device. The heat exchanger 300 serves a
function of a heat transport fluid, enabling a continually flowing
pumped loop with continuously applied electric fields.
[0022] It is to be appreciated that performance of the field-active
liquid material can be increased by utilizing a mixture of
dielectric constituents, both liquid and solid, to improve entropy
change and/or extend operating temperature range. For example,
particles of an electrocaloric ceramic with large pyroelectric
effect can be mixed into an active electrocaloric liquid crystal
with lower performance to create a slurry, gaining the performance
advantage of the solid material while retaining the system
flexibility advantage of using a liquid. In addition to the
features of a slurry of an electrocaloric ceramic with an active
electrocaloric liquid, other embodiments can include an inactive
liquid dielectric material that is added to a solid elcctrocaloric
material for the purpose of creating a flowable mixture. As an
additional example, two or more different liquid crystals with
different active temperature ranges may be mixed to broaden the
temperature response of the liquid mixture in the system. As an
additional example, additives may be used to lower input
requirements for entropy change, such as nanoparticles to lower
required field strength. Also, solid-state pumping technology such
as electrophoretic pumping could be used to create an entirely
solid-state cooling device.
[0023] FIG. 4 illustrates an exemplary variation of a system 400
that uses a regenerative heat exchanger to achieve higher
temperature lift than that enabled by the physical properties of
the field-active liquid material. System 400 includes a
regenerative heat exchanger 402 (or regenerator 402) that includes
a regenerative matrix made from a solid material that stores heat
and acts as an electrode, imposing an electric field on the
field-active liquid. A field active liquid reciprocates
back-and-forth between bracketed respective hot and cold heat
exchangers 404 and 406 and through the regenerative heat exchanger
402 in synchronization with the applied electric field to develop a
temperature gradient in the regenerator and thus increase the
temperature difference between heat exchangers 404 and 406. The
field-active liquid material can be translated back and forth
through the regenerator 402 by an imposed pressure field generated
by a mechanical or electrostatic pump or linear actuator.
[0024] Heat exchangers 404 and 406 can include electrodes to apply
an electric field to the field-active liquid material. Unlike any
other regenerative cycle, the reciprocating field-active liquid is
best maintained under constant field, either on or off, when the
liquid is reciprocated from regenerator 402 toward either heat
exchangers 404 and 406. When the regenerator is energized and the
liquid is translated toward one heat exchanger, that heat exchanger
will also be energized. This requires integration of the three heat
exchangers 402, 404, and 406 and specific spatial-temporal
synchronization of the applied field.
[0025] In operation, application of the field through intimate
contact to the field-active liquid in regenerator 402 may increase
the material entropy (e.g., temperature). Advecting the now hot
field-active liquid into the hot heat exchanger 404 while also
maintaining the field in the heat exchanger 404 causes it to reject
heat to the hot ambient 408. Once the heat exchanger 404 cools to
the hot ambient 408 temperature, the field in the regenerator 402
is released causing the field-active liquid to cool. The field in
hot heat exchanger 404 is also de-energized causing the
field-active material inside to cool. Advecting the now cooled
field-active material from the hot exchanger 404 toward the cold
heat exchanger 406 causes the field-active material to absorb heat
from the cold ambient 410 and complete the cycle. The performance
of the system 400 may depend on timing and synchronization of the
applied field and flow, and that such timing may change with
thermal properties of the material, the load, and the temperature
lift desired, so careful control of this process may be needed to
achieve satisfactory performance.
[0026] The regenerator matrix can be made with field-active
materials to create a hybrid liquid-solid matrix, increasing the
heat pumping capacity and power density. In one embodiment the
regenerator matrix 402 is made from electrically insulating
electroactive ceramic or polymer with electrodes on each side and
the field-active liquid between the layers. Energizing these
electrodes activate both liquid and solid field-active material
simultaneously for increased capacity. In another embodiment the
regenerator matrix 402 can be made from active solid magnetocaloric
materials, elastocaloric materials, or optocaloric materials.
Electric field applied to activate the electroactive liquid
material is synchronized with a separately applied magnetic,
strain, or light field, respectively, to the solid matrix to
produce additional capacity. In another embodiment, heat exchangers
404 and 406 can also be made from solid field-active material and
energized with the field-active regenerator matrix and field-active
liquid to further increase capacity.
[0027] FIG. 5 illustrates an exemplary hybridized system 500 for
use in accordance with embodiments of the invention. System 500
illustrates two repeating elements 502 and 504 of a multi-channel
regenerative heat exchanger that utilizes combinations of liquid
and solid electrocaloric materials as well as materials sensitive
to other fields such as magnetic, strain, pressure or radiation
fields. In an example for regenerator element 502, a solid matrix
503 of the regenerator 502 can be made of electrocaloric material
such as ferroelectric ceramics or polymers. This material provides
thermal storage needed for regeneration as well as providing
support for the electrodes 506 and 508. A pair of electrodes 506
and 508 can energize the electrocaloric solid. A pair of electrodes
508 and 510 can energize the electrocaloric liquid 512 flowing
between a pair of solid matrices in regenerator elements 502 and
504. These electrodes, e.g., electrodes 506, 508, and 510 can
simultaneously energize both the field-active liquid (e.g.,
electrocaloric liquid) and the field-active solid material of the
regenerator matrix, in effect offsetting the parasitic thermal
dilutive effect of the regenerator material and thus increasing the
specific capacity of the device. In another embodiment, the
electrode pairs 506/508 and 508/510 can be energized in sequence to
provide additional temperature lift.
[0028] In order to use the principle of offsetting parasitic loss
of the regenerator matrix, a solid material can be used which
exhibits entropy change in fields other than electric for the
regenerator matrix. Use of a magnetocaloric material or material
that changes entropy when exposed to strain, pressure, or radiation
(including light) as the regenerator matrix and electrode support,
combined with the imposition of the respective field synchronized
with the electric field imposed on the liquid electrocaloric
material, can also increase specific capacity of the device.
Similarly, an electrocaloric solid material could be superposed
with an optically energized liquid material.
[0029] Using a field-active liquid material serves a function of a
heat transport fluid, enabling a continually flowing pumped loop
with continuously applied electric fields as described in the
embodiments described above in FIGS. 2-3. However, using
regeneration to multiply temperature lift as described in the
embodiments described above in FIGS. 4-5 requires a less efficient
reciprocating fluid motion as well as potentially inefficient
temporal variation of the electric field. To achieve high
temperature lift with continuous fluid flow and electric field, and
thus improved efficiency, a cascaded cycle concept with
appropriately integrated heat exchangers is used as is described in
FIG. 6.
[0030] FIGS. 6A-6C illustrate an exemplary regenerator system 600
that integrates multiple electrocaloric loops through coupling heat
transfer in accordance with an embodiment of the invention. System
600 integrates many individual electrocaloric loops through
coupling heat transfers using an electrocaloric liquid crystal but,
in embodiments, other field-active liquid materials may also be
utilized. As seen in FIG. 6A, a first electrocaloric loop is
illustrated where a cold secondary fluid or ambient is connected
through a heat exchanger 604 with the de-energized end 608 of an
electrocaloric loop 602 which is driven by a liquid pump 606. In
some non-limiting examples, pump 606 can be a mechanical pump, an
electrostatic electric field pump, an electrophoretic electric
field pump, or the like. The electrocaloric loop 602 will
continually transport heat from the low ambient to a higher
temperature. The energized (or hot) end 610 of the loop 602 is in a
heat exchange relationship with another heat exchange element 612
to the cold end of another independent loop 614 to pump heat to an
even higher temperature as illustrated in FIG. 6B. Similarly, as
illustrated in FIG. 6C, an energized hot end 616 of loop 614 is in
a heat exchange relationship through another heat exchange element
618 to the cold end of another independent loop 620 to pump heat to
an even higher temperature. This process continues with another
connection between low ambient to a higher temperature through an
electrocaloric loop until adequate temperature lift is achieved and
then the hot end of the last loop is connected to the hot secondary
fluid or ambient through heat exchanger 622.
[0031] As shown in FIGS. 6A-6C, combination of electrocaloric loops
602, 614, and 620 is enabled by stacking layers of loops and heat
exchangers and then using headers to connect the channels together
such that many parallel loops can be driven by one pump, which is
similar to brazed or welded plate-fin, minichannel, or compact heat
exchanger fabrication known in the industry. In embodiments, a
multichannel pump such as a peristaltic pump or other modular pomp
could be used to drive flow through multiple cascade elements using
a single motor and speed control. The system 600 allows heat
pumping while maintaining continuous active fluid and secondary
fluid flows combined with steadily applied electric fields to avoid
any wasteful reversal of flow or current. Again, many physical
embodiments may provide the same functionality of bringing active
primary and secondary fluids together at the appropriate
temperatures for heat transfer resulting in additional lift.
[0032] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. While the description of the present invention has
been presented for purposes of illustration and description, it is
not intended to be exhaustive or limited to the invention in the
form disclosed. Many modifications, variations, alterations,
substitutions, or equivalent arrangement not hereto described will
be apparent to those of ordinary skill in the art without departing
from the scope and spirit of the invention. Additionally, while
various embodiments of the invention have been described, it is to
be understood that aspects of the invention may include only some
of the described embodiments. Accordingly, the invention is not to
be seen as limited by the foregoing description, but is only
limited by the scope of the appended claims.
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