U.S. patent application number 12/763745 was filed with the patent office on 2011-10-20 for standing wave thermoacoustic piezoelectric refrigerator.
This patent application is currently assigned to KING ABDUL AZIZ CITY FOR SCIENCE AND TECHNOLOGY. Invention is credited to OSAMA J. ALDRAIHEM.
Application Number | 20110252810 12/763745 |
Document ID | / |
Family ID | 44787078 |
Filed Date | 2011-10-20 |
United States Patent
Application |
20110252810 |
Kind Code |
A1 |
ALDRAIHEM; OSAMA J. |
October 20, 2011 |
STANDING WAVE THERMOACOUSTIC PIEZOELECTRIC REFRIGERATOR
Abstract
A standing wave thermoacoustic piezoelectric refrigerator is
provided. The standing wave thermoacoustic piezoelectric
refrigerator includes a housing, a porous stack, and a
piezoelectric bimorph. The housing comprises a compressible fluid
and has a first portion and a second portion. The porous stack is
positioned between a hot heat exchanger and a cold heat exchanger
within the housing, at an end of the first portion of the housing
opposite to an end of the first portion having the porous stack and
is capable of oscillating to generate acoustic energy upon
receiving energy from an external energy source. The oscillation of
the piezoelectric bimorph compresses and expands the compressible
fluid within the housing. Whereby, the compressible fluid traverses
between the first portion and the second portion through the porous
stack to generate standing acoustic waves enabling the compressible
fluid to transfer heat from the cold heat exchanger to the hot heat
exchanger.
Inventors: |
ALDRAIHEM; OSAMA J.;
(RIYADH, SA) |
Assignee: |
KING ABDUL AZIZ CITY FOR SCIENCE
AND TECHNOLOGY
RIYADH
SA
|
Family ID: |
44787078 |
Appl. No.: |
12/763745 |
Filed: |
April 20, 2010 |
Current U.S.
Class: |
62/3.1 ;
62/235.1; 62/6 |
Current CPC
Class: |
F25B 2309/1407 20130101;
F25B 9/145 20130101; F25B 2309/1402 20130101 |
Class at
Publication: |
62/3.1 ; 62/6;
62/235.1 |
International
Class: |
F25B 21/00 20060101
F25B021/00; F25B 27/00 20060101 F25B027/00; F25B 9/00 20060101
F25B009/00 |
Claims
1. A standing wave thermoacoustic piezoelectric refrigerator
comprising: a housing comprising a compressible fluid, the housing
having a first portion and a second portion; a porous stack
configured within the housing, the porous stack positioned between
a hot heat exchanger and a cold heat exchanger configured within
the housing; and a piezoelectric bimorph configured at an end of
the first portion of the housing opposite to an end of the first
portion having the porous stack, the piezoelectric bimorph is
capable of oscillating to generate acoustic energy, the
piezoelectric bimorph oscillates for compressing and expanding the
compressible fluid within the housing upon receiving energy from an
external energy source, whereby the compressible fluid traverses
between the first portion and the second portion through the porous
stack to generate standing acoustic waves thereby enabling the
compressible fluid to transfer heat from the cold heat exchanger to
the hot heat exchanger based on the standing acoustic waves.
2. The standing wave thermoacoustic piezoelectric refrigerator of
claim 1, wherein the external energy source is one of electrical
energy and solar energy.
3. The standing wave thermoacoustic piezoelectric refrigerator of
claim 1, wherein the energy supplied by the external energy source
to the piezoelectric bimorph is varied based on a threshold
oscillation frequency of the piezoelectric bimorph to develop the
standing acoustic waves in the first portion of the housing, the
threshold oscillation frequency is associated with resonating
frequency of the first portion of the housing.
4. The standing wave thermoacoustic piezoelectric refrigerator of
claim 1, wherein temperature of at least one of the hot heat
exchanger and the cold heat exchanger is varied to generate the
standing acoustic waves in the first portion of the housing.
5. The standing wave thermoacoustic piezoelectric refrigerator of
claim 1, wherein the porous stack comprises at least one of metal
foils, a metal mesh, a sheet of a foamed metal, and sheets of
filter paper.
6. The standing wave thermoacoustic piezoelectric refrigerator of
claim 1, wherein the compressible fluid is one of air and
helium.
7. The standing wave thermoacoustic piezoelectric refrigerator of
claim 1, wherein a configuration of the first portion of the
housing is one of a straight configuration and an optimally shaped
configuration.
8. The standing wave thermoacoustic piezoelectric refrigerator of
claim 1, wherein a configuration of the second portion of the
housing is one of a straight configuration and an optimally shaped
configuration.
9. The standing wave thermoacoustic piezoelectric refrigerator of
claim 1, wherein a cross sectional shape associated with at least
one of the first portion and the second portion of the housing is
one of a circle, a square, a rectangle, and a polygon.
Description
FIELD OF THE INVENTION
[0001] The invention generally relates to refrigeration, and more
specifically, to a standing wave thermoacoustic piezoelectric
refrigerator for refrigeration by utilizing standing acoustic
waves.
BACKGROUND OF THE INVENTION
[0002] Thermoacoustic engines are commonly used as heat pumps or
refrigerators, they utilize energy associated with thermoacoustic
waves for refrigeration process.
[0003] In existing technologies, usually thermoacoustic
refrigerators utilize energy associated with the thermoacoustic
waves to transfer heat from a lower temperature end to a higher
temperature end. Such thermoacoustic refrigerators use transducers
as acoustic drivers for utilizing the acoustic energy. Further, the
thermoacoustic refrigerators use a hot heat exchanger and a cold
heat exchanger. A porous structure may be configured between the
hot heat exchanger and the cold heat exchanger. The porous
structure is made up of one or more of metal foils, a metal mesh, a
sheet of a foamed metal, and sheets of filter paper. Additionally,
the thermoacoustic refrigerators may include one or more moving
parts and moving masses to generate the thermoacoustic waves. These
one or more moving parts and moving masses require sliding seal
mechanisms for their operation. The thermoacoustic waves may be
generated within the thermoacoustic refrigerators using mechanism
used for generating sonic waves. The thermoacoustic waves thus
generated are utilized to trigger the heat from the lower
temperature end to the higher temperature end.
[0004] Further, a free piston mechanism may be used to reduce
complexities in using the one or more moving parts and moving
masses in the thermoacoustic refrigerators to generate the
thermoacoustic waves. The free piston mechanism in the
thermoacoustic refrigerators utilizes gas springs to generate
thermoacoustic waves. The gas springs in the thermoacoustic
refrigerators work similar to mechanical pistons, thereby,
partially eliminating the need of sliding seal mechanisms. However,
the use of moving masses in the thermoacoustic refrigerators is
still required in such thermoacoustic refrigerators.
[0005] Therefore, there is a need for a system for efficiently
performing refrigeration process using thermoacoustic energy.
BRIEF DESCRIPTION OF THE FIGURES
[0006] The accompanying figures, where like reference numerals
refer to identical or functionally similar elements throughout the
separate views and which together with the detailed description
below are incorporated in and form part of the specification, serve
to further illustrate various embodiments and to explain various
principles and advantages all in accordance with the invention.
[0007] FIG. 1A illustrates a standing wave thermoacoustic
piezoelectric refrigerator in accordance with an embodiment of the
invention.
[0008] FIG. 1B illustrates a standing acoustic wave generated
within a standing wave thermoacoustic piezoelectric refrigerator in
accordance with an embodiment of the invention.
[0009] FIG. 2A illustrates a thermodynamic cycle of a fluid parcel
of a compressible fluid inside a standing wave thermoacoustic
piezoelectric refrigerator for generating standing acoustic waves
in accordance with another embodiment of the invention.
[0010] FIG. 2B that illustrates a Pressure-Volume (P-V) diagram
associated with the thermodynamic cycle of the fluid parcel for
generating the standing acoustic waves.
[0011] FIG. 3A illustrates a thermodynamics cycle of a fluid parcel
of a compressible fluid inside a porous stack within a standing
wave thermoacoustic piezoelectric refrigerator in accordance with
an embodiment of the invention.
[0012] FIG. 3B illustrates a Pressure-Volume (P-V) diagram
associated with the thermodynamic cycle of the fluid parcel inside
the porous stack.
[0013] Skilled artisans will appreciate that elements in the
figures are illustrated for simplicity and clarity and have not
necessarily been drawn to scale. For example, the dimensions of
some of the elements in the figures may be exaggerated relative to
other elements to help to improve understanding of embodiments of
the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0014] Before describing in detail embodiments that are in
accordance with the invention, it should be observed that the
embodiments reside primarily in combinations of apparatus
components related to a standing wave thermoacoustic piezoelectric
refrigerator. Accordingly, the apparatus components have been
represented where appropriate by conventional symbols in the
drawings, showing only those specific details that are pertinent to
understanding the embodiments of the invention so as not to obscure
the disclosure with details that will be readily apparent to those
of ordinary skill in the art having the benefit of the description
herein.
[0015] In this document, relational terms such as first and second,
top and bottom, and the like may be used solely to distinguish one
entity or action from another entity or action without necessarily
requiring or implying any actual such relationship or order between
such entities or actions. The terms "comprises," "comprising," or
any other variation thereof, are intended to cover a non-exclusive
inclusion, such that a process, method, article, or apparatus that
comprises a list of elements does not include only those elements
but may include other elements not expressly listed or inherent to
such process, method, article, or apparatus. An element proceeded
by "comprises . . . a" does not, without more constraints, preclude
the existence of additional identical elements in the process,
method, article, or apparatus that comprises the element.
[0016] Generally speaking, pursuant to various embodiments, the
invention provides a standing wave thermoacoustic piezoelectric
refrigerator. The standing wave thermoacoustic piezoelectric
refrigerator includes a housing. The housing includes a
compressible fluid. Additionally, the housing has a first portion
and a second portion. Further, the standing wave thermoacoustic
piezoelectric refrigerator includes a porous stack within the
housing. The porous stack is positioned between a hot heat
exchanger and a cold heat exchanger within the housing. The
standing wave thermoacoustic piezoelectric refrigerator also
includes a piezoelectric bimorph at an end of the first portion of
the housing. The piezoelectric bimorph is configured opposite to an
end of the first portion having the porous stack. The piezoelectric
bimorph is capable of oscillating to generate acoustic energy upon
receiving energy from an external energy source. Due to the
oscillation of the piezoelectric bimorph the compressible fluid
compresses and expands within the housing. This enables the
compressible fluid to traverse between the first portion and the
second portion through the porous stack to generate standing
acoustic waves. The standing acoustic waves enable the compressible
fluid to transfer heat from the cold heat exchanger to the hot heat
exchanger.
[0017] Referring to drawings and in particular to FIG. 1A, a
standing wave thermoacoustic piezoelectric refrigerator 100 is
illustrated in accordance with an embodiment of the invention.
Standing wave thermoacoustic piezoelectric refrigerator 100
includes a housing 102. Housing 102 includes a compressible fluid
104. Compressible fluid 104 is one of air and a helium gas. It may
be apparent to a person skilled in the art that any other gases may
be used as a compressible fluid in housing 102. Further, housing
102 includes a first portion 106 and a second portion 108. A
configuration of first portion 106 of housing 102 may be one of a
straight configuration and an optimally shaped configuration. In an
embodiment, first portion 106 may be optimally shaped to have a
tapered configuration. Similarly, a configuration of second portion
108 of housing 102 may be one of a straight configuration and an
optimally shaped configuration. In an embodiment, second portion
108 may be optimally shaped to have a tapered configuration.
[0018] Additionally, a cross-sectional shape associated with one or
more of first portion 106 and second portion 108 may be one of a
circle, a square, a rectangle, and a polygon. For example, in a
scenario, first portion 106 may have a tapered configuration with a
circular cross section and second portion 108 may have a tapered
configuration with a circular cross section. Alternatively, first
portion 106 and second portion 108 may have a different
configuration and cross-sectional shape. For example, first portion
106 may have a straight configuration and a rectangular
cross-sectional shape, and second portion 108 may have a tapered
configuration and a circular cross-sectional shape.
[0019] Standing wave thermoacoustic piezoelectric refrigerator 100
may further include a porous stack 112. Porous stack 112 may
include one or more of, but are not limited to, metal foils, a
metal mesh, a sheet of a foamed metal, and a sheet of filter paper.
Porous stack 112 is positioned between a hot heat exchanger 114 and
a cold heat exchanger 116 within housing 102. For example, porous
stack 112 may be configured such that hot heat exchanger 114 is
positioned near one end of porous stack 112 and cold heat exchanger
116 is positioned near another end of porous stack 112 opposite to
the end of porous stack 112 where hot heat exchanger 114 is
positioned. Hot heat exchanger 114 is configured within second
portion 106. In an embodiment, hot heat exchanger 114 may be at an
ambient temperature. Cold heat exchanger 116 is configured within
first portion 108. Hot heat exchanger 114 and cold heat exchanger
116 facilitates in creation of a temperature gradient between first
portion 106 and second portion 108 within housing 102.
[0020] Further, standing wave thermoacoustic piezoelectric
refrigerator 100 includes a piezoelectric bimorph 118 at an end of
first portion 106. Piezoelectric bimorph 118 is configured at an
end of first portion 106 opposite to an end of first portion 106
where porous stack 112 is configured. Piezoelectric bimorph 118
oscillates upon receiving energy from an external energy source.
The external energy source may include one of, but not limited to,
electrical energy and solar energy. Piezoelectric bimorph 118 may
be oscillated by an existing system known in the art. The existing
system may be capable of utilizing the external energy source to
oscillate piezoelectric bimorph 118. Thus, the amount of
oscillation of piezoelectric bimorph 118 may be based on the amount
of energy supplied by the external energy source. For example, in
an instance, frequency of oscillations of piezoelectric bimorph 118
may be increased by increasing the frequency of energy supplied to
piezoelectric bimorph 118. In another instance, intensity of
oscillations of piezoelectric bimorph 118 may be increased by
increasing amount of energy supplied to piezoelectric bimorph
118.
[0021] Due to the oscillation of piezoelectric bimorph 118,
compressible fluid 104 compresses and expands within housing 102.
Compressible fluid 104 traverses between first portion 106 and
second portion 108 through porous stack 112 in response to the
compression and expansion of compressible fluid 104. Thereafter, a
cyclic transformation takes place inside compressible fluid 104.
The cyclic transformation includes compression, heating, expansion,
and cooling of one or more of fluid parcels of compressible fluid
104 within housing 102. A cyclic transformation of the one or more
fluid parcels in a standing wave thermoacoustic piezoelectric
refrigerator is explained in detail in conjunction with FIG. 2A and
FIG. 2B.
[0022] The cyclic transformation of compressible fluid 104 results
in the generation of two acoustic waves, such as, an acoustic wave
120 and an acoustic wave 122 as shown in FIG. 1B. A first portion
of standing wave thermoacoustic piezoelectric refrigerator 100 is
shown along an axis X-X' that cuts standing wave thermoacoustic
piezoelectric refrigerator 100. Acoustic wave 120 and acoustic wave
122 travel in opposite direction within first portion 106. Acoustic
wave 120 and acoustic wave 122 may have different frequencies. When
the frequencies of acoustic wave 120 and acoustic wave 122 match,
standing acoustic waves are generated within first portion 106 of
housing 102. In an exemplary embodiment, two acoustic waves are
generated inside the first portion of the standing wave
thermoacoustic piezoelectric refrigerator. One of the two acoustic
waves having frequency 15 Hz may travel towards the porous stack
and another acoustic wave of the two acoustic waves having
frequency of 20 Hz may travel towards the piezoelectric bimorph. A
standing acoustic wave may be generated when both of the two
acoustic waves have same frequencies. In this case, a standing
acoustic wave may be generated when frequency of one acoustic wave
matches the frequency of another acoustic wave.
[0023] An instance of the standing acoustic waves within standing
wave thermoacoustic piezoelectric refrigerator 100 is illustrated
in FIG. 1B. The standing acoustic wave as illustrated in FIG. 1B
may have one cycle. It will be apparent to a person skilled in the
art that the standing acoustic wave may have any number of cycles
within the standing wave thermoacoustic piezoelectric apparatus.
Further, when the standing acoustic wave is created, there may be a
phase difference of 90.degree. between velocity of the one or more
fluid parcels of compressible fluid 104 and pressure of the one or
more fluid parcels of compressible fluid 104. In other words,
velocity associated with the one or more fluid parcels of
compressible fluid 104 may be negligible when the pressure
associated with the one or more fluid parcels is at a maximum level
or a minimum level. These standing acoustic waves generated are
used to transfer heat from cold heat exchanger 116 to hot heat
exchanger 114 using compressible fluid 104.
[0024] In an embodiment, frequency associated with the standing
acoustic waves generated within first portion 106 may be changed
based on dimension of one or more of first portion 106 and second
portion 108. The dimension of first portion 106 includes one or
more of, but not limited to, configuration of first portion 106,
cross-sectional shape of first portion 106, and length of first
portion 106. Similarly, the dimension of second portion 108
includes one or more of, but not limited to, configuration of
second portion 108, cross-sectional shape of second portion 108,
and length of second portion 108. For example, frequency of
standing acoustic waves in a standing wave thermoacoustic
piezoelectric apparatus having a long first portion may be less as
compared to frequency of standing acoustic waves in a standing wave
thermoacoustic piezoelectric apparatus having a short first
portion.
[0025] In an embodiment, the energy supplied by the external energy
source to piezoelectric bimorph 118 may be varied to generate the
standing acoustic waves in first portion 106 of housing 102. For
example, in an instance, the temperature level of cold heat
exchanger 116 may start increasing, thereby resulting in a need to
further cool cold heat exchanger 116. This increase in temperature
of cold heat exchanger 116 may also result in slow down of
refrigeration process. To decrease the temperature of cold heat
exchanger 116, standing acoustic waves of high intensity are
generated. The high intensity standing acoustic waves may be
generated by increasing the energy supplied by the external energy
source to piezoelectric bimorph 118. This high intensity standing
acoustic waves facilitates in transfer of heat from cold heat
exchanger 116 to hot heat exchanger 114 thereby accelerating the
refrigeration process.
[0026] In another embodiment, the energy supplied by the external
energy source to piezoelectric bimorph 118 may be varied based on a
threshold oscillation frequency of piezoelectric bimorph 118. The
threshold oscillation frequency is associated with a resonating
frequency of first portion 106 of housing 102. For example, the
threshold oscillation frequency indicates a frequency associated
with first portion 106 of the housing for generating a quarter
cycle of the standing acoustic waves. However, it will be apparent
to a person skilled in the art that the threshold oscillation
frequency of the housing may indicate a frequency for generating
any number of cycles of the standing acoustic waves.
[0027] In still another embodiment, temperature associated with hot
heat exchanger 114 may be varied to generate the standing acoustic
waves in first portion 106 of housing 102. For example, the
temperature level of hot heat exchanger 114 may increase upon
receiving heat from cold heat exchanger 116. This may result in
heat transfer from hot heat exchanger 114 to one or more fluid
parcels of compressible fluid 104 near hot heat exchanger 114. When
the one or more fluid parcels travel towards cold heat exchanger
116, heat may traverse an area near hot heat exchanger 114 to an
area near cold heat exchanger 116. To decrease the traversal of
heat from hot heat exchanger 114 to cold heat exchanger 116,
temperature within hot heat exchanger 114 may be decreased. The
decrease in temperature of hot heat exchanger 114 reduces
temperature difference between hot heat exchanger 114 and cold heat
exchanger 116. This may in turn reduce a need of high intensity
standing acoustic waves to transfer heat from cold heat exchanger
116 to hot heat exchanger 114.
[0028] In an embodiment, temperature associated with cold heat
exchanger 116 may be varied to generate the standing acoustic waves
in first portion 106 of housing 102. For example, the temperature
level of cold heat exchanger 116 may start increasing, thereby
resulting in need of further cooling of cold heat exchanger 116.
This increase in temperature of cold heat exchanger 116 may also
result in slow down of refrigeration process. This may also result
in a need of standing acoustic waves of high intensity to transfer
heat from cold heat exchanger 116 to hot heat exchanger 114. To
trigger the refrigeration process, the temperature within cold heat
exchanger 116 is decreased. This may reduce the need of high
intensity standing acoustic waves to transfer heat from cold heat
exchanger 116 to hot heat exchanger 114.
[0029] In another embodiment, the temperature of compressible fluid
104 may be varied to generate the standing acoustic waves within
first portion 106 of housing 102. The temperature of compressible
fluid 104 may be varied by varying temperature of surrounding of
standing wave thermoacoustic piezoelectric apparatus 100. For
example, in order to match the frequencies of the two acoustic
waves travelling in opposite direction, the temperature of
surrounding is increased to generate the standing acoustic waves
within first portion 106.
[0030] Standing wave thermoacoustic piezoelectric refrigerator 100
uses piezoelectric bimorph 114 and includes fixed parts for the
refrigeration process. The use of such fixed parts eliminates the
need of sliding seal mechanisms. Further, referring back to
optimally shaped configuration of one or more of first portion 106
and second portion 108 of standing wave thermoacoustic
piezoelectric refrigerator 100, a tapered configuration of one or
more of first portion 106 and second portion 108 increases the
intensity of the standing acoustic waves generated in first portion
106 and second portion 108. This reduces the need of high frequency
oscillation of piezoelectric bimorph 118 for creating high
intensity standing acoustic waves.
[0031] Turning now to FIG. 2A that illustrates a thermodynamic
cycle of a fluid parcel 200 of a compressible fluid inside a
standing wave thermoacoustic piezoelectric refrigerator for
generating standing acoustic waves and FIG. 2B that illustrates a
Pressure-Volume (P-V) diagram 202 associated with the thermodynamic
cycle of fluid parcel 200 in accordance with an embodiment of the
invention. The thermodynamics cycle indicates a cyclic
transformation undergone by fluid parcel 200 of the compressible
fluid such as, compressible fluid 104 within the standing wave
thermoacoustic piezoelectric refrigerator such as, standing wave
thermoacoustic piezoelectric refrigerator 100. The cyclic
transformation includes compression of fluid parcel 200, heating of
fluid parcel 200, expansion of fluid parcel 200, and cooling of
fluid parcel 200. Further, during the cyclic transformation of
fluid parcel 200, a pressure and a volume associated with fluid
parcel 200 changes and such changes in the pressure and the volume
is indicated in Pressure-Volume diagram 202.
[0032] The cyclic transformation of fluid parcel 200 takes place
based on oscillation of a piezoelectric bimorph such as,
piezoelectric bimorph 118 within the standing wave thermoacoustic
piezoelectric refrigerator such as, standing wave thermoacoustic
piezoelectric refrigerator 100. The oscillation of the
piezoelectric bimorph is triggered upon receiving energy from an
external energy source. This is explained in detail in conjunction
with FIG. 1A.
[0033] Due to the oscillation of the piezoelectric bimorph, the
cyclic transformation of the compressible fluid takes place. During
the cyclic transformation, the compressible fluid traverses between
a first portion such as, first portion 106 and a second portion
such as, second portion 108 of a housing such as, housing 102 of
standing wave thermoacoustic piezoelectric refrigerator 100. Based
on the oscillation, when the piezoelectric bimorph moves inward,
one or more fluid parcels of the compressible fluid near the
piezoelectric bimorph pushes the compressible fluid away from the
piezoelectric bimorph. This results in compression of fluid parcel
200 inside the housing at stage 204. The compression of fluid
parcel 200 decreases the volume of fluid parcel 200 and increases
the pressure of fluid parcel 200. This reduction in the volume and
increase in the pressure is indicated by stage 204 as shown in P-V
diagram 202. At stage 206, fluid parcel 200 collects heat in
response to the compression of fluid parcel 200. This results in
heating of fluid parcel 200 at a constant volume. The heating of
fluid parcel 200 is indicated by stage 206 as shown in P-V diagram
202. At this stage, the pressure of fluid parcel 200 is maximum and
a velocity of fluid parcel 200 is negligible.
[0034] Meanwhile, as the piezoelectric bimorph moves outward based
on the oscillation of the piezoelectric bimorph, the one or more
fluid parcels of the compressible fluid near the piezoelectric
bimorph pulls the compressible fluid towards the piezoelectric
bimorph. This results in expansion of fluid parcel 200 inside the
housing at stage 208. The expansion of fluid parcel 200 decreases
the pressure of fluid parcel 200 and increases the volume of fluid
parcel 200. This reduction in the pressure and increase in the
volume is indicated by stage 208 as shown in P-V diagram 202.
Thereafter, at stage 210, fluid parcel 200 dispatches heat in
response to the expansion of fluid parcel 200. This results in
cooling of fluid parcel 200 at constant volume. The cooling of
fluid parcel 200 is indicated by stage 210 as shown in P-V diagram
202. At this stage, the pressure of fluid parcel is minimum and the
velocity of fluid parcel is negligible. Subsequently, the
piezoelectric bimorph again moves inwards based on the oscillation.
This further result in compression of fluid parcel 200 in the
housing similar to stage 204. As a result, the cyclic
transformation of fluid parcel 200 occurs within the standing wave
thermoacoustic piezoelectric refrigerator.
[0035] During the cyclic transformation inside the compressible
fluid, the compression and expansion of the one or more fluid
parcels of the compressible fluid results in back and forth
movement of the one or more fluid parcels along the standing wave
thermoacoustic piezoelectric refrigerator. The back and forth
movement of the one or more fluid parcels generate two acoustic
waves within the housing. The two acoustic waves travel in opposite
directions as one acoustic wave of the two acoustic waves is a
reflection of another acoustic wave of the two acoustic waves. When
the frequencies of the two acoustic waves match, standing acoustic
waves are created within the first portion of the housing. This is
explained in detail in conjunction with FIG. 1A and FIG. 1B. The
standing acoustic waves thus created enable the compressible fluid
inside the porous stack to transfer heat from a cold heat exchanger
such as, cold heat exchanger 116 to a hot heat exchanger such as,
hot heat exchanger 114.
[0036] Referring now to FIG. 3A that illustrates a thermodynamics
cycle of a fluid parcel 300 of a compressible fluid inside a porous
stack within a standing wave thermoacoustic piezoelectric
refrigerator and FIG. 3B that illustrates a Pressure-Volume (P-V)
diagram 302 for the thermodynamic cycle of fluid parcel 300 inside
the porous stack within the standing wave thermoacoustic
piezoelectric refrigerator in accordance with an embodiment of the
invention. The thermodynamic cycle indicates a cyclic
transformation undergone by fluid parcel 300 of the compressible
fluid such as, compressible fluid 104 inside the porous stack such
as, porous stack 112 within the standing wave thermoacoustic
piezoelectric refrigerator such as, standing wave thermoacoustic
piezoelectric refrigerator 100. The cyclic transformation of fluid
parcel 300 is due to the heat transfer from the cold heat exchanger
to the hot heat exchanger through the porous stack. The transfer of
heat from the cold heat exchanger to the hot heat exchanger is
triggered upon generation of the standing acoustic waves. Further,
during the cyclic transformation of fluid parcel 300, a pressure
and volume associated with fluid parcel 300 changes and such
changes in the pressure and the volume is illustrated in P-V
diagram 302.
[0037] Due to the standing acoustic waves, fluid parcel 300
traverses between the cold heat exchanger to the hot heat exchanger
through the porous stack of the standing wave thermoacoustic
piezoelectric refrigerator. The standing acoustic waves enables one
or more fluid parcels of the compressible fluid present near the
cold heat exchanger to push fluid parcel 300 thereby decreasing the
volume of fluid parcel 300. These one or more fluid parcels may
have maximum velocity when they are travelling away from the cold
heat exchanger. Thereafter, fluid parcel 300 starts traveling
towards the hot heat exchanger from the cold heat exchanger. This
results in compression of fluid parcel 300 at stage 304. The
compression of fluid parcel 300 decreases the volume of fluid
parcel 300 and increases the pressure of fluid parcel 300. This
reduction in the volume and increase in the pressure is indicated
by stage 304 as shown in P-V diagram 302 in FIG. 3B. Towards the
end of stage 304 temperature of fluid parcel 300 is higher as
compared to temperature of walls of the porous stack near fluid
parcel 300. At stage 306, fluid parcel 300 dispatches heat to one
or more of the hot heat exchanger and the walls of the porous
stack. This results in cooling of fluid parcel 300. The cooling of
fluid parcel 300 is indicated by stage 306 as shown in P-V diagram
302 in FIG. 3B.
[0038] Further, when the standing acoustic waves pulls one or more
fluid parcels of the compressible fluid near the cold heat
exchanger, volume of fluid parcel 300 starts increasing. In this
case, the one or more fluid parcels of the compressible fluid may
have maximum velocity while traveling towards the cold heat
exchanger. Thereafter, fluid parcel 300 starts traveling towards
the cold heat exchanger. This results in expansion of fluid parcel
300 at stage 308. The expansion of fluid parcel 300 increases the
volume of fluid parcel 300 and decreases the pressure of fluid
parcel 300. This increase in the volume and reduction in the
pressure is indicated by stage 308 as shown in P-V diagram 302.
Towards the end of stage 308 temperature of fluid parcel 300 is
lower as compared to temperature of the walls of the porous stack
near fluid parcel 300. At stage 310, fluid parcel receives heat
from one or more of the cold heat exchanger and the walls of the
porous stack. This results in heating of fluid parcel 300 and
cooling of the cold heat exchanger. The heating of fluid parcel 300
is indicated by stage 310 as shown in P-V diagram 302. In the
meanwhile, the standing acoustic waves again push fluid parcel 300
towards the hot heat exchanger from the cold heat exchanger similar
to stage 304. As a result, a cyclic transformation of fluid parcel
300 occurs inside the porous stack within the standing wave
thermoacoustic piezoelectric refrigerator. This cyclic
transformation of one or more fluid parcels within the porous stack
contributes to the refrigeration process.
[0039] Various embodiments of the invention provide a standing wave
thermoacoustic piezoelectric refrigerator for refrigeration
process. The standing wave thermoacoustic piezoelectric
refrigerator uses a piezoelectric bimorph. As a result, the
frequency of oscillation of the piezoelectric bimorph is easily
controlled to trigger the refrigeration process. Further, the
standing wave thermoacoustic piezoelectric refrigerator uses
piezoelectric bimorph along with fixed parts thereby eliminating
the need of sliding seal mechanisms. Moreover, one or more of a
first portion and a second portion of the standing wave
thermoacoustic piezoelectric refrigerator may have tapered
configuration. The tapered configuration facilitates in increasing
the intensity of the standing acoustic waves generated in the first
portion thereby reducing the amount of energy required to oscillate
the piezoelectric bimorph.
[0040] Those skilled in the art will realize that the above
recognized advantages and other advantages described herein are
merely exemplary and are not meant to be a complete rendering of
all of the advantages of the various embodiments of the
invention.
[0041] In the foregoing specification, specific embodiments of the
invention have been described. However, one of ordinary skill in
the art appreciates that various modifications and changes can be
made without departing from the scope of the invention as set forth
in the claims below. Accordingly, the specification and figures are
to be regarded in an illustrative rather than a restrictive sense,
and all such modifications are intended to be included within the
scope of the invention. The benefits, advantages, solutions to
problems, and any element(s) that may cause any benefit, advantage,
or solution to occur or become more pronounced are not to be
construed as a critical, required, or essential features or
elements of any or all the claims. The invention is defined solely
by the appended claims including any amendments made during the
pendency of this application and all equivalents of those claims as
issued.
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