U.S. patent application number 11/904679 was filed with the patent office on 2009-04-02 for controlled and variable gas phase shifting cryocooler.
Invention is credited to David G.T Curran, Sidney W.K. Yuan.
Application Number | 20090084115 11/904679 |
Document ID | / |
Family ID | 40506658 |
Filed Date | 2009-04-02 |
United States Patent
Application |
20090084115 |
Kind Code |
A1 |
Yuan; Sidney W.K. ; et
al. |
April 2, 2009 |
Controlled and variable gas phase shifting cryocooler
Abstract
Cryocoolers, including coolers, heaters, and heat pumps each
having a first stage and a second stage, are modified with
controlled and variable gas phase shifting devices for controlling
gas pressure and mass flow between volumes of the first and second
stages for improving the efficiency and temperature range of
expander cryocoolers such as displacer cryocoolers using controlled
valves as flow impedance devices and pulse tube cryocoolers using
inertance gaps as flow inertia devices, for maximizing cooling
between the first and second stages.
Inventors: |
Yuan; Sidney W.K.; (Los
Angeles, CA) ; Curran; David G.T; (Pacific Palisades,
CA) |
Correspondence
Address: |
Carole A. Mulchinski;M1/040
The Aerospace Corporation, 2350 East El Segundo Boulevard
El Segundo
CA
90245
US
|
Family ID: |
40506658 |
Appl. No.: |
11/904679 |
Filed: |
September 28, 2007 |
Current U.S.
Class: |
62/6 |
Current CPC
Class: |
F25B 2309/1424 20130101;
F25B 2309/1408 20130101; F25B 9/145 20130101; F25B 2309/1418
20130101; F25B 9/14 20130101 |
Class at
Publication: |
62/6 |
International
Class: |
F25B 9/00 20060101
F25B009/00 |
Claims
1. A cryocooler a first volume and a second volume, the cryocooler
comprising, a first stage defining a first volume for containing
gas at a first temperature and first pressure, and a second stage
defining a second volume for containing the gas at a second
temperature and second pressure, and a gas phase shifting device
between the first volume and the second volume, the gas phase
shifting device providing a pressure and temperature phase
difference between the first volume and the second volume, and a
controller for controlling the gas phase shifting device for
controlling the pressure and temperature phase difference between
the first volume and the second volume.
2. The cryocooler of claim 1 wherein, the cryocooler is selected
from a group consisting of coolers, heaters, and heat pumps.
3. The cryocooler of claim 1 wherein, gas mass flow in the first
volume exit is in phase with the gas pressure.
4. The cryocooler of claim 1 wherein, the cryocooler is a displacer
cryocooler, the first stage is a moving first heat exchanger, and
the second stage is a moving second heat exchanger.
5. The cryocooler of claim 1 wherein, the cryocooler comprises a
compressor, the cryocooler is a displacer cryocooler, the first
stage is a moving first heat exchanger, the second stage is a
moving second heat exchanger, and the moving first heat exchanger
and the second stage heat exchanger are portions of a porous piston
driving gas pressure and mass flow from a compressor.
6. The cryocooler of claim 1 wherein the cryocooler is a pulse tube
cryocooler, the gas phase shifting device is an inertance gap, the
first stage comprising stationary heat exchanger and an exit volume
as the first volume, the second stage comprises a pulse tube, the
gas phase shifting device, and a reservoir volume, and the
reservoir volume is the second volume.
7. The cryocooler of claim 1 wherein the cryocooler comprises a
compressor, the cryocooler is a pulse tube cryocooler, the gas
phase shifting device is an inertance gap, the first stage
comprising stationary heat exchanger and an exit volume as the
first volume, the second stage comprises a pulse tube, the gas
phase shifting device, and a reservoir volume, the reservoir volume
being the second volume, and the compressor injects gas through the
stationary heat exchanger and exit volume and through the pulse
tube and through the inertance gap and into the reservoir.
8. The cryocooler of claim 1 wherein, the cryocooler is a displacer
cryocooler, the gas phase shifting device is a flow impedance
device, and the flow impedance device is controlled by the
controller.
9. The cryocooler of claim 1 wherein, the cryocooler is a displacer
cryocooler, the gas phase shifting device is a valve, and the valve
is controlled by the controller.
10. The cryocooler of claim 1 wherein, the cryocooler is a
displacer cryocooler, the gas phase shifting device is an orifice,
and the orifice is controlled by the controller.
11. The cryocooler of claim 1 wherein, the cryocooler is a
displacer cryocooler, the gas phase shifting device is a flow
inertance device, and the flow inertance device is controlled by
the controller.
12. The cryocooler of claim 1 wherein, the cryocooler is a
displacer cryocooler, the gas phase shifting device is an inertance
gap, and the inertance gap is controlled by the controller.
13. The cryocooler of claim 1 wherein, the cryocooler is selected
from the group consisting of displacer cryocoolers and pulse tube
cryocoolers, and the gas phase shifting device is selected from the
group consisting of flow impedance devices and flow inertance
devices.
14. The cryocooler of claim 1 wherein, the cryocooler is a pulse
tube cryocooler, the gas phase shifting device is a flow inertance
device, and the flow inertance device is controlled by the
controller.
15. The cryocooler of claim 1 wherein, the cryocooler is a pulse
tube cryocooler, the gas phase shifting device is an inertance gap,
and the inertance gap device is controlled by the controller.
16. The cryocooler of claim 1 wherein, the cryocooler is a pulse
tube cryocooler, the gas phase shifting device is an inertance gap,
and a dimension of the inertance gap is controlled by a motor
controlled by the controller.
17. The cryocooler of claim 1 wherein, the cryocooler is a pulse
tube cryocooler, the gas phase shifting device is an inertance gap,
a dimension of the inertance gap is controlled by a motor being
controlled by the controller, and the motor is selected from the
group consisting of electromechanical motors and thermal
motors.
18. The cryocooler of claim 1 wherein, the cryocooler is a pulse
tube cryocooler, the gas phase shifting device is an inertance gap,
a dimension of the inertance gap is controlled by a motor being
controlled by the controller, the dimension being selected from the
group consisting of width, length, and thickness, and the motor is
selected from the group consisting of electromechanical motors and
thermal motors.
19. The cryocooler of claim 1 wherein, the controller controls the
gas phase shifting device over time for time varying the pressure
and temperature phase difference between the first volume and the
second volume.
Description
REFERENCE TO RELATED APPLICATION
[0001] The present application is related to applicant's copending
applications entitled Gas Phase Shifting Multistage Displacer
Cryocooler, Ser. No. ______, filed ______, Controlled and Variable
Gas Phase Shifting Cryocooler Ser. No. ______, filed ______, and
Gas Phase Shifting Inertance Gap Pulse Tube Cryocooler, Ser. No.
______, filed ______, by the same inventors.
FIELD OF THE INVENTION
[0002] The invention relates to the field of refrigeration systems.
More particularly, the invention relates to cryocoolers providing
phase shifting of gas pressures using controlled gas phase shifting
devices in a multiple stage expander cryocooler and multiple stage
pulse tube cryocooler for improved energy transfer and cooling
efficiencies.
BACKGROUND OF THE INVENTION
[0003] Cryocoolers are mechanical machines used for cooling,
heating, and thermal transfer. The cryocoolers typically have
multiple internal volumes for heating and cooling. Multistage
coolers are coolers with more than one cooling or heating stage
having more than one volume. Mechanical cryocoolers can be
classified according to the type of heat exchangers used, that is,
regenerative versus recuperative. Regenerative mechanical
cryocoolers can be further classified according to the presence or
absence of valves, thermal compressors, or mechanical compressors,
and the presence or absence of displacers, such as pulse tubes.
Multistage cryocoolers are routinely used for reaching temperatures
below what a single stage cryocooler can achieve. The staging of
cryocoolers can be done in parallel or in series.
[0004] Relevant cryocoolers include displacer cryocoolers and pulse
tube cryocoolers. A displacer cryocooler is generally comprised of
a compressor connected to an expander. The expander may be a
multistage heat exchanger. The compressor and expander are
connected together with or without transfer tubes. A pulse tube
cryocooler includes a stationary regenerator connected to a pulse
tube that includes a long inertance tube.
[0005] The displacer cryocooler is driven by a compressor, which
sends a pressure wave to the displacer. In a multistage displacer
cryocooler, the first stage of the expander pre-cools the gas that
enters the second stage, and the second stage pre-cools the gas
that enters the third stage, and so on. The cooling capacity at
each stage is directly proportional to the swept volume of the
expansion space. Because the cross-sectional areas of the expansion
spaces are fixed in a given multistage mechanical cryocooler
design, the ratio of heat loads among the stages that the
cryocooler can cool is also fixed. Limited shifting of loads can be
achieved by changing the frequency, charge pressure, or temperature
at each stage.
[0006] The efficient pulse tube cryocooler consists of a long
inertance tube that may be up to several meters in length between
the warm end of the pulse tube and a buffer volume. Pulse tube
coolers are reliable primarily because pulse tube coolers do not
have any cold moving parts, or displacers, or valves that can
break. A compressor drives a piston that provides the energy needed
for the refrigeration. As the piston compresses, a parcel of warm
gas travels through the regenerator. The gas is cooled by the
matrix of the regenerator, that is, the heat exchanger. Part of the
heat from compression Q.sub.o is removed at ambient temperature.
The gas is then expanded through the pulse tube and the orifice
into the buffer or reservoir volume. Expansion provides cooling
Q.sub.c that takes place at temperature T.sub.c. Because the pulse
tube does not have a displacer, phase shifting is accomplished by a
combination of the orifice and the buffer volume. Theoretically,
maximum cooling efficiency is accomplished with the pressure wave
in phase with respect to mass flow at the cold end of the
cryocooler. The performance of the orifice pulse tube can be
enhanced by incorporating double inlets or bypasses. Moreover, in
replacing the orifice with a long capillary known as the inertance
tube, the performance of the cooler can be improved by avoiding
irreversible losses associated with a sharp edged orifice. With a
sharp edged orifice, the only variable parameter is the diameter of
the orifice, limiting heat exchange control. With an inertance
tube, there are two variables consisting of the length and diameter
of the tube. The phase shift mechanism can be modeled using an LRC
circuit analogy. Inductance L=4 L.sub.t/(.pi.d.sub.t.sup.2) is
analog to a flow inertance. Resistance R is analogous to flow
impedance. Capacitance C=Mv.sub.t/(.gamma.RT) is analog to the
fluid heat capacity. The tube geometry can be defined where L.sub.t
is the gap length, d.sub.t and v.sub.t are the length, diameter and
internal volume of the inertance tube, .eta. is viscosity, .SIGMA.
is density, and .gamma. is the specific heat ratio, T is the
temperature, and M is the molecular weight. The long inertance tube
is used to optimize the gas phase shift. Unfortunately, the long
tube geometry is also cumbersome, heavy, and bulky. The long
inertance tube does not readily provide the means for optimizing
the gas phase shift between the compressor and reservoir for
various applications, which requires different cooling capacity.
The tuning of the gas phase shift is only by setting the length and
diameter of the inertance tube. Accordingly, there are two ways to
add inductance, that is, the analogous inertance. One way to add
inertance is by increasing the length L.sub.t or by decreasing the
diameter d.sub.t. Because resistance is inversely proportional to
the fourth power of diameter d.sub.t, decreasing d.sub.t will
increase resistance substantially. Additionally, inertance can be
increased by increasing the length of tube, but this
disadvantageously results in a long and slender tube.
[0007] Pulse tube systems with inertance tubes have been studied
both theoretically and experimentally. The flow circuit in a pulse
tube is analogous to that of an electrical circuit. The optimum
phase shifting can be obtained by introducing an inertance term
into the circuit, instead of relying on a pure resistance circuit
caused by a pressure drop in a sharp edged orifice used for phase
shifting. The pulse tube system includes an exchanger stage coupled
to a pulse tube that is coupled to a reservoir. The pulse tube
system disadvantageously includes an elongated inertance tube
having a length that is longer than a meter in most applications.
The packaging of a long tube presents problems as well as in
applications where vibration, such as during a launch, may cause
failure of the cooler.
[0008] US Patent Publication No. 20050022539 teaches incorporating
a hybrid cryocooler with a first stage expander and a second stage
pulse tube design. Because the pulse tube cryocooler uses an
orifice or inertance tube between the pulse tube and the surge
volume to optimize cooling, the hybrid design provides an extra
parameter for load shifting. Expander cryocoolers are in general
more efficient than pulse tube cryocoolers, however, the displacer
cryocoolers are less reliable due to the presence of a moving
displacer. The hybrid design tends to combine the main disadvantage
of a expander cryocooler with that of a pulse tube cryocooler.
[0009] Mechanical cryocoolers are used extensively for cooling
purposes. Multistage coolers are generally used to reach
temperatures below 35.degree. K. The shifting of loads between
stages is not flexible in a multistage mechanical cryocooler. Thus,
there is disadvantageously a limited range of temperature that each
stage can achieve relative to other stages. These and other
disadvantages are solved or reduced using this invention.
SUMMARY OF THE INVENTION
[0010] An object of the invention is to provide gas phase shifting
in a mechanical device.
[0011] Another object of the invention is to provide controlled gas
phase shifting using a flow impedance device in a cryocooler.
[0012] Yet another object of the invention is to provide controlled
gas phase shifting using a flow inertia device in a cryocooler.
[0013] Also another object of the invention is to provide gas phase
shifting using an inertance gap in a pulse tube cryocooler.
[0014] Still another object of the invention is to provide gas
phase shifting using an impedance device in a multistage displacer
cryocooler.
[0015] Furthermore, another object of the invention is to provide
gas phase shifting using an inertance device in a multistage
displacer cryocooler.
[0016] The invention is directed to gas phase shifting in
cryocoolers for improved cooling efficiency. In a first aspect, a
valve is disposed between stage volumes in a multistage displacer
cryocooler. In a second aspect, inertance gaps are disposed in line
of a pulse tube cryocooler. A gas phase shifting means is installed
between different volumes of the stages of the cryocooler allowing
the cryocooler to operate with wider heat loads and temperature
ranges. The gas phase shifting device provides for load shifting
between the stages in a multistage mechanical cryocooler. In a
displacer cryocooler, the gas phase shifting can be achieved by
installing a phase shifting device between the expansion volumes.
The gas phase shifting device can be a flow impedance device, for
example, a valve, a sharp-edged orifice, or a porous medium in an
expander cryocooler. The gas phase shifting device can also be a
flow inertia device, for example, an inertance gap in a pulse tube
of a cryocooler. The gas phase shifting device phase shift the gas
pressure in phase with mass flow at the cold end of the cryocooler
for maximum cooling. These and other advantages will become more
apparent from the following detailed description of the preferred
embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a diagram of a two-stage gas phase shifting
cryocooler.
[0018] FIG. 2 is a diagram of a pulse tube gas phase shifting
inertance gap cryocooler.
[0019] FIG. 3A is a diagram of a concentric ring inertance gap.
[0020] FIG. 3B is a diagram of a parallel plate inertance gap.
[0021] FIG. 4A is a diagram of a motor controlled variable
inertance gap.
[0022] FIG. 4B is a diagram of a heater controlled variable
inertance gap.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0023] An embodiment of the invention is described with reference
to the figures using reference designations as shown in the
figures. Referring to FIG. 1, a two-stage gas phase shifting valve
cryocooler is a modified version of a conventional two-stage cooler
with a moving porous piston heat exchanger. The porous piston heat
exchanger, or simply the regenerator, functions as a heat
exchanger. The porous piston is bifurcated for heat exchange into a
first stage heat exchanger for exchange heat with a first stage
volume and into a second stage heat exchanger for heat exchange
with a second stage volume. A compressor provides the pressure and
volume work required for cooling, by moving the piston. The
compressor injects gas through an intake conduit into an empty
volume, known as a plenum. The gas is cooled when passing through
the porous heat exchanger. The piston in the cryocooler moves when
a parcel of gas is admitted into the plenum through the intake
conduit. The parcel of gas then passes through the first stage
porous piston heat exchanger being a first stage regenerator into
the first stage volume, known as an expander volume. When passing
through the piston, the gas exchanges heat with the matrix of the
porous piston and is cooled in a first stage regenerator. The gas
is cooled further as the expander increases in volume. Part of the
admitted gas continues to pass through the second stage porous
piston heat exchanger for further cooling into the second stage
volume that is also an expander volume for further cooling. When
passing through the second stage heat exchanger, the gas exchanges
heat with the matrix of the heat exchanger and is further cooled.
The motion of the porous piston heat exchanger is driven
pneumatically by the compressor or separately by a motor, not
shown. The motion of the porous piston heat exchanger is driven
with a phase lag relative to the compressor motion. When the
compressor compresses, gas is admitted into the plenum. As the
porous piston heat exchanger moves towards the plenum, expansion
takes place at the first and second stage expander volumes,
resulting in cooling. The compression and expansion of the first
and second stage volumes are synchronized. Thus, the temperature of
the second stage of the cooler is influenced by the temperature of
the first stage, and vice versa.
[0024] A controlled gas phase shifting device can be a controlled
valve or orifice opening that is a resistance device, or a
controlled tube or gap geometry that is an inertance device. For
maximum cooling, the gas pressure is in phase with mass flow at the
cold end of the cryocooler. The gas mass flow of gas moving from
the first stage to the second stage is in phase with the pressure
difference between the first stage and the second stage. The gas
phase shifting devices mentioned above are controlled by a
controller that controls gas flow through a first stage conduit
connected to the first stage volume and a second stage conduit
connected to the second stage volume. The valve controls partial
gas flows between the first and second expander volumes. The
partial gas flows create a phase shift in gas pressures and mass
flow between the first and second volumes. The valve or orifice
resistance device, or a tube or gap inertance device disposed
between the first stage conduit and second stage conduit, functions
as a gas phase shifting device. By introducing this phase shifting
device between the first and second stage volumes, a wider
temperature range of one stage relative to the other can be
achieved. The phase shifting device can be a gas resistance device
such as valves and orifices, or an inertance device such as tubes
and gaps. Different settings of valve opening and orifice size for
resistance devices, and diameter, length, width, and thickness of
gaps, or the diameter and the length of the tube for inertance can
be used to optimize cooler performance. While shown for two stages,
one or more phase shifting devices can be applied to any number of
expander volumes in including those having more than two stages and
respective volumes.
[0025] Referring to FIG. 2, a pulse tube cooler is characterized as
having a pulse tube coupled between a stationary first stage heat
exchanger and a reservoir. A compressor drives gas through the
first stage heat exchanger or regenerator. Four tubes are used to
couple in line the compressor to the heat exchanger, to the pulse
tube, to the inertance gap, and finally to the reservoir. The
reservoir is coupled to an inertance gap through a first tube. The
inertance gap is coupled to a pulse tube through a second tube. The
pulse tube is connected to a heat exchanger through a third tube.
The heat exchanger is coupled to a compressor through a fourth
tube. The compressor includes a piston driven by a load. The
compressor provides the gas pressure work required to achieve
cooling. The heat exchanger and third tube can be considered a
first stage and the pulse tube and the inertance gap can be
considered a second stage. As such, the third tube defines an
entrance volume as a first stage volume. The entrance of the fourth
tube is a hot end and the exit of the third tube is a cold end of
the first stage. The reservoir is an exit volume as a second stage
volume.
[0026] When the piston in the compressor compresses, a parcel of
gas is admitted into the regenerating heat exchanger through the
intake conduit, that is, the fourth tube. As the gas passes through
the heat exchanger, the gas exchanges heat with the matrix, not
shown, within the heat exchanger and is cooled. The cooled gas is
then passed to the pulse tube that is an empty tube. As the gas
moves from the third tube end into the pulse tube and then to the
reservoir through the inertance gap, expansion of the gas occurs
resulting in cooling of the gas in the third tube. There is created
pressure gas phase lag between the compression of the gas at the
compressor and expansion of the gas through the inertance gap to
the reservoir for optimal cooling. The inertance gap is used in
place of an inertance tube. Variously configured inertance gaps can
be used.
[0027] Referring to FIGS. 3A, 3B, 4A, and 4B in sequence, the
inertance gap can be made of concentric elongated rings. The gap
thickness between the rings, the diameter of the rings, and the
length of the rings, define the gap geometry, and hence, define the
gas phase shifting capability. The gap can also be fashioned out of
parallel plates defining a planar inertance gap. In both the
concentric ring configuration and the parallel plate configuration,
the gap geometry is compact and light in weight. The compact gap
design offers the capability of optimizing the phase shift for
different applications by varying the gap size. For in-operation
adaptations, the gap can be made dynamic and precisely externally
controlled when desired. A gap can be defined as between a gap
piston and gap housing. A variable gap is realized by moving the
piston within a gap housing. A motive means can be used to drive
the gap piston toward or away from the housing to vary the
thickness of the gap. That is, the position of the gap piston in
relation to the gap housing defines the gap thickness. The position
of the gap can be varied mechanically by using the motive means
that can be in the exemplar forms a motor using electrical power or
thermal expander that is powered by differences in thermal
contraction coefficients. Likewise, in a controlled inertance tube
device, the geometry of the tube can also be changed, for example,
by using a bellows tube.
[0028] Referring to all of the Figures, the gas phase shifting
cryocooler provides more efficient cooling at each stage in a
multistage displacer cryocooler. The gas phase shifting in the
displacer cryocooler can be achieved by installing a phase shifting
device between the expansion spaces. For the displacer cryocooler,
the exemplar gas phase shifting device can be a flow resistance
device, for example, a valve, a sharp-edge orifice, or a porous
medium. The gas phase shifting device can also be a flow inertia
device, for example, a long capillary or an inertance gap.
Likewise, the gas phase shifting pulse tube cryocooler provides
more efficient cooling in a pulse tube cooler. The gas phase
shifting in the pulse tube cryocooler can be achieved by an
inertance gap installed between the pulse tube and the reservoir.
For the pulse tube cryocooler, the exemplar gas phase shifting
device is a defined gap preferably having at least three degrees of
design freedom for optimizing the gas phase shifting. In both the
displacer cryocooler and the pulse tube cryocooler, the gas phase
shifting device can be externally controlled such as by using a
controlled valve or a controlled inertance gap changing the gas
shifting characteristics for improved cooler performance.
[0029] In a pulse tube cryocooler, an inertance gap is placed
between the warm end of the pulse tube and the surge buffer
reservoir. Exemplar gaps include concentric ring inertance gaps and
parallel plate inertance gaps. The inertance gap is defined as a
geometry with the thickness of the opening much smaller than the
width or length of the opening. As such, the inertance gap provides
three variables consisting of a thickness Sg, a length Lg, and a
width Wg of the gap having a volume Vg. The analogous LRC equations
become L=L.sub.g/(W.sub.gS.sub.g), R=12
L.sub.g.eta./.SIGMA.W.sub.gS.sup.3), and C=Mv/(.gamma.RT). Relating
the inertance gap parameters to the inertance tube parameters,
Lg=(4 Wt/.pi.) (S.sub.g/d.sub.t.sup.2)L.sub.t. The length of the
inertance gap Lg is orders of magnitude (S.sub.g/d.sub.t.sup.2)
smaller than the length of the inertance tube L.sub.t. The
performance of the inertance gap pulse tube is more efficient than
that of the inertance tube pulse tube at high powers, and is
slightly less efficient at low powers. Moreover, the design of the
inertance gap can be more compact, such as a few inches in length,
compared to that of the inertance tube that can be a few meters in
length.
[0030] The performance of a cryocooler can be predicted using
commercial cryocooler software tools. For a two-stage displacer
cryocooler, the first stage heat load can be plotted as a function
of the first stage temperature and the second stage heat load
plotted as a function of the second stage temperature. In both
stages, the cryocooler with the phase shifting device offers a
wider operating temperature range and a higher cooling
capacity.
[0031] The gas phase shifting cryocooler provides improved cooler
performance. The addition of a control valve or orifice or
controlled inertance tube or gap between expansion volumes in a
displacer cryocooler, or the placement of an inertance gap in a
pulse tube cryocooler, can provide improved cooler performance. The
gap design substantially decreases the length of the phase shifting
device reducing packaging constraints and the potential for
vibration failures. The performance of the inertance gap in the
pulse tube cooler is improved at high powers. By further optimizing
the performance with a different geometry of the inertance gap, the
gas phase shifting cryocooler can approach or surpass the
performance of an inertance tube pulse tube cooler. The controlled
gas phase shifting cryocooler enables real-time optimization of the
performance of the pulse tube subject to different operating
conditions by varying the gap size remotely through a thermal or
electromechanical means. It is more practical to vary the inertance
gap size rather than the dimensions of a long inertance tube.
Instead of setting the dimensions of a valve or orifice or the
inertance gap at discrete values throughout the entire
thermodynamic cycle, the dimensions of the controlled gas phase
shifting device can also be varied within the thermodynamic cycle,
resulting in a time variant phase shifting device.
[0032] A pulse tube with a compact inertance gap, which replaces
the long inertance tube offers comparable performance, but is much
more compact, easier to package, without any vibration failures
while offering real-time performance optimization capability.
Various gaps designed can be used in a pulse tube cryocooler
between the pulse tube and the reservoir. For example tapered,
series, and parallel gaps could be used in various configurations.
Various gas phase-shifting devices, such as a controlled valve or
orifice, or inertance gap or tube can be used between expander
volumes in displacer cryocooler. The preferred forms are
cryocoolers and heat pumps. Those skilled in the art can make
enhancements, improvements, and modifications to the invention, and
these enhancements, improvements, and modifications may nonetheless
fall within the spirit and scope of the following claims.
* * * * *