U.S. patent application number 12/742751 was filed with the patent office on 2010-10-21 for cryogenic refrigeration method and device.
This patent application is currently assigned to L'Air Liquide Societe Anonyme Pour L'Etude Et L'Exploitation Des Procedes Georges Claude. Invention is credited to Fabien Durand, Alain Ravex.
Application Number | 20100263405 12/742751 |
Document ID | / |
Family ID | 39691274 |
Filed Date | 2010-10-21 |
United States Patent
Application |
20100263405 |
Kind Code |
A1 |
Durand; Fabien ; et
al. |
October 21, 2010 |
Cryogenic Refrigeration Method And Device
Abstract
The invention relates to a cryogenic refrigeration device
intended to transfer heat from a cold source to a hot source via a
working fluid flowing through a closed working circuit including
the following portions in series, namely: a portion for the
substantially isothermal compression of the fluid, a portion for
the substantially isobaric cooling of the fluid, a portion for the
substantially isothermal expansion of the fluid, and a portion for
the substantially isobaric heating of the fluid. The compression
portion of the working circuit includes at least two compressors
disposed in series and the expansion portion of the working circuit
includes at least one expansion turbine, said compressors and
expansion turbine(s) being driven by at least one high-speed motor
including an output shaft. One end of the output shaft supports and
rotates, by means of direct coupling, a first compressor, while the
other end of the output shaft supports and rotates, by means of
direct coupling, a second compressor or an expansion turbine.
Inventors: |
Durand; Fabien; (Voreppe,
FR) ; Ravex; Alain; (Meylan, FR) |
Correspondence
Address: |
AIR LIQUIDE USA LLC;Intellectual Property
2700 POST OAK BOULEVARD, SUITE 1800
HOUSTON
TX
77056
US
|
Assignee: |
L'Air Liquide Societe Anonyme Pour
L'Etude Et L'Exploitation Des Procedes Georges Claude
Paris
FR
|
Family ID: |
39691274 |
Appl. No.: |
12/742751 |
Filed: |
October 23, 2008 |
PCT Filed: |
October 23, 2008 |
PCT NO: |
PCT/FR2008/051919 |
371 Date: |
May 13, 2010 |
Current U.S.
Class: |
62/510 ; 62/498;
62/6 |
Current CPC
Class: |
F25J 1/0276 20130101;
F25B 1/10 20130101; F25B 9/10 20130101; F25J 1/0075 20130101; F25J
1/0095 20130101; F25J 2230/20 20130101; F25J 1/0097 20130101; F25J
1/0257 20130101; F25J 1/0279 20130101; F25B 9/14 20130101; F25J
1/0065 20130101; F25J 2270/16 20130101; F25B 2309/1401 20130101;
F25J 1/0288 20130101; F25J 1/0072 20130101; F25J 1/0062 20130101;
F25B 9/06 20130101; F25J 2270/912 20130101; F25J 1/005 20130101;
F25J 1/0077 20130101; F25J 2230/22 20130101; F25J 1/0082 20130101;
F25J 2240/02 20130101; F25J 1/0284 20130101; F25J 1/0287
20130101 |
Class at
Publication: |
62/510 ; 62/6;
62/498 |
International
Class: |
F25B 1/10 20060101
F25B001/10; F25B 9/14 20060101 F25B009/14; F25B 9/10 20060101
F25B009/10 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 23, 2007 |
FR |
0759243 |
Claims
1-10. (canceled)
11: A cryogenic refrigeration device for transferring heat from a
cold source to a hot source via a working fluid flowing through a
closed working circuit, the working circuit comprising in series;
a) a portion for the substantially isothermal compression of the
fluid, b) a portion for the substantially isobaric cooling of the
fluid, c) a portion for the substantially isothermal expansion of
the fluid, and d) a portion for the substantially isobaric heating
of the fluid, the compression portion of the working circuit
comprising; e) at least two compressors disposed in series and f)
at least one heat exchanger for cooling the compressed fluid
disposed at the outlet of each compressor, the expansion portion of
the working circuit comprising; g) at least one expansion turbine
and h) at least one heat exchanger for heating the expanded fluid,
wherein the compressors and the expansion turbine(s) are driven by
at least one high-speed comprising; i) an output shaft whereof one
end supports and rotates, by means of direct coupling, j) a first
compressor and whereof the other end supports and rotates, by means
of direct coupling, k) a second compressor or an expansion turbine,
and in that l) the compressors are of the centrifugal compression
type, and in that m) the expansion turbine(s) are of the
centripetal expansion type, and in that n) the output shafts of the
motors are mounted on magnetic or dynamic gas bearings, said
bearings being used to support the compressors and the turbine sand
in that o) the cooling portion and the heating portion comprise a
common heat exchanger through which the working fluid flows in
countercurrent according to whether it is cooled or heated.
12: The device of claim 11, wherein the working circuit comprises a
volume forming a buffer storage chamber for the working fluid.
13: The device of claim 11, wherein the working fluid is in the gas
phase and is composed of a pure gas or a mixture of pure gases
selected from the group consisting of: helium, neon, nitrogen,
oxygen, argon, carbon monoxide, methane, or any other fluid having
a gas phase at the temperature of the cold source.
14: The device of claim 11, wherein the number of compression
stages is higher than the number of expansion stages.
15: The device of any claim 11, further comprising at least one
motor whereof at least one end of the output shaft rotates, by
means of direct coupling, at least two wheels.
16: The device of claim 15, further comprising at least one motor
whereof one end of its output shaft rotates, by means of direct
coupling, two compressor impellers, the other end of the output
shaft rotating, by means of direct coupling, a turbine wheel.
17: A cryogenic refrigeration method for transferring heat from a
cold source to a hot source via a working fluid flowing through a
closed working circuit, the working circuit comprising in series;
a) providing a compression portion comprising at least two
compressors disposed in series, b) providing a fluid cooling
portion, c) providing an expansion portion comprising at least one
expansion turbine, and d) providing a heating portion, the method
comprising a working cycle comprising; e) compressing,
substantially isothermally, the fluid in the compression portion by
cooling the compressed fluid at the outlet of the compressors, f)
cooling, substantially isobaricly, the fluid in the cooling
portion, g) expanding, substantially isothermally, the fluid in the
expansion portion by heating the expanded fluid at the turbine
outlet, and h) heating, substantially isobaricly, the fluid having
exchanged heat with the cold source), the fluid working cycle
(temperature T, entropy S) being of the reverse Ericsson type, i)
cooling, during the first substantially isothermal compression
step, the compressed fluid at the outlet of each compressor to keep
the fluid temperatures at the inlet and outlet of each compressor
substantially equal and preferably within a range of about 10 K, j)
cooling, during the third substantially isothermal expansion step,
the expanded fluid at the outlet of each turbine to keep the fluid
temperatures at the inlet and outlet of each turbine substantially
equal and preferably within a range of about 5 K, k) driving the
compressors and the expansion turbine(s) by at least one high-speed
motor comprising an output shaft whereof one end supports and
rotates, by means of direct coupling, a first compressor and
whereof the other end supports and rotates, by means of direct
coupling, a second compressor or an expansion turbine, and in that
l) transferring part of the mechanical work of the turbine(s) to
the compressor(s) via the output shaft(s), and in that m) mounting
the output shafts of the motors on magnetic or dynamic gas
bearings, said bearings being used to support the compressors and
turbines, and in that the cooling portion and the heating portion
comprise a common heat exchanger through which the working fluid
flows in countercurrent according to whether it is cooled or
heated.
18: The method of claim 17, wherein on completion of the second
cooling step, the working fluid is cooled to a low temperature of
about 60 K and in that the working circuit comprises a number of
compressors that is three times higher than the number of expansion
turbines.
19: The method of claim 17, wherein the working fluid is used to
cool or to keep cold superconductor elements at a temperature of
about 65 K.
20: The method of claim 17 wherein the temperature drop of the
fluid constituting the cold source is substantially identical to
the temperature rise of the working gas in heat exchanger
Description
[0001] The present invention relates to a cryogenic refrigeration
device and method.
[0002] The invention relates more particularly to a cryogenic
refrigeration device for transferring heat from a cold source to a
hot source via a working fluid flowing in a closed working circuit,
the working circuit comprising in series: a compression portion, a
cooling portion, an expansion portion and a heating portion.
[0003] The cold source may for example be liquid nitrogen for
cooling and the hot source water or air.
[0004] Refrigerators known for cooling superconductor elements
generally use a reverse Brayton cycle. These known refrigerators
use a lubricated rotary screw compressor, a countercurrent plate
heat exchanger and an expansion turbine.
[0005] These known refrigerators have many drawbacks including:
[0006] low energy efficiency of the cycle and hence of the
refrigerator, [0007] the use of oil to cool and lubricate the
compressor, which imposes a de-oiling of the working gas after
compression, [0008] the use of rotary seals between the electric
motor and the compressor, [0009] the low isothermal compression
efficiency of the compressor, [0010] the frequency of maintenance
operations.
[0011] Document U.S. Pat. No. 3,494,145 describes a refrigeration
system using couplings via gears requiring oil-lubricated bearings.
This type of device uses rotary seals such as mechanical seals
between the working gas and the gear housing and oil bearings. This
architecture increases the risks of leakage of the working gas and
the potential pollution of the working gas by the oil. This system
is also associated with a low-speed motor.
[0012] Document U.S. Pat. No. 4,984,432 describes a refrigeration
system using compressors or liquid seal turbines operating with a
low-speed motor using conventional bearings such as ball bearings.
This technology is associated with positive displacement
compressors and turbines.
[0013] It is an object of the present invention to overcome all or
some of the drawbacks of the prior art identified above.
[0014] For this purpose, the invention proposes a cryogenic
refrigeration device for transferring heat from a cold source to a
hot source via a working fluid flowing through a closed working
circuit, the working circuit comprising in series: a portion for
the substantially isothermal compression of the fluid, a portion
for the substantially isobaric cooling of the fluid, a portion for
the substantially isothermal expansion of the fluid, and a portion
for the substantially isobaric heating of the fluid, the
compression portion of the working circuit comprising at least two
compressors disposed in series and at least one heat exchanger for
cooling the compressed fluid disposed at the outlet of each
compressor, the expansion portion of the working circuit comprising
at least one expansion turbine and at least one heat exchanger for
heating the expanded fluid, the compressors and the expansion
turbine(s) being driven by at least one high-speed motor comprising
an output shaft whereof one end supports and rotates, by means of
direct coupling, a first compressor and whereof the other end
supports and rotates, by means of direct coupling, a second
compressor or an expansion turbine.
[0015] The embodiments serve to obtain a system without oil
pollution and without contact. This is because the combination of
centrifugal compressors, centripetal turbines and bearings
according to the invention reduces or eliminates any contact with
the fixed parts and the rotating parts. This serves to avoid any
risk of leakage. The overall system is in fact hermetically sealed
and does not comprise any rotary seal with regard to the atmosphere
(such as mechanical seals or dry face seals).
[0016] Moreover, embodiments of the invention may comprise one or
more of the following features: [0017] the compressors are of the
centrifugal compression type, [0018] the expansion turbine(s) are
of the centripetal expansion type, [0019] the output shafts of the
motors are mounted on magnetic bearings or on dynamic gas bearings,
said bearings being used to support the compressors and the
turbines, [0020] the cooling portion and the heating portion
comprise a common heat exchanger through which the working fluid
flows in countercurrent according to whether it is cooled or
heated, [0021] the working circuit comprises a volume forming a
buffer storage chamber for the working fluid, [0022] the working
fluid is in the gas phase and is composed of a pure gas or a
mixture of pure gases selected from: helium, neon, nitrogen,
oxygen, argon, carbon monoxide, methane, or any other fluid having
a gas phase at the temperature of the cold source.
[0023] The invention further proposes a cryogenic refrigeration
method for transferring heat from a cold source to a hot source via
a working fluid flowing through a closed working circuit, the
working circuit comprising in series: a compression portion
comprising at least two compressors disposed in series, a fluid
cooling portion, an expansion portion comprising at least one
expansion turbine, and a heating portion, the method comprising a
working cycle comprising a first step of substantially isothermal
compression of the fluid in the compression portion by cooling the
compressed fluid at the outlet of the compressors, a second step of
substantially isobaric cooling of the fluid in the cooling portion,
a third step of substantially isothermal expansion of the fluid in
the expansion portion by heating the expanded fluid at the turbine
outlet, and a fourth step of substantially isobaric heating of the
fluid having exchanged heat with the cold source, the fluid working
cycle (temperature T, entropy S) being of the reverse Ericsson
type.
[0024] Furthermore, embodiments of the invention may comprise one
or more of the following features: [0025] during the first
substantially isothermal compression step, the compressed fluid is
cooled at the outlet of each compressor to keep the fluid
temperatures at the inlet and outlet of each compressor
substantially equal and preferably within a range of about 10 K,
[0026] during the third substantially isothermal expansion step the
expanded fluid is cooled at the outlet of each turbine to keep the
fluid temperatures at the inlet and outlet of each turbine
substantially equal and preferably within a range of about 5 K,
[0027] the compressors and the expansion turbine(s) are driven by
at least one high-speed motor comprising an output shaft whereof
one end supports and rotates, by means of direct coupling, a first
compressor and whereof the other end supports and rotates, by means
of direct coupling, a second compressor or an expansion turbine,
and in that the method comprises a step of transfer of part of the
mechanical work of the turbine(s) to the compressor(s) via the
output shaft(s), [0028] on completion of the second cooling step,
the working fluid is cooled to a low temperature of about 60 K and
in that the working circuit comprises a number of compressors that
is about three times higher than the number of expansion turbines,
[0029] the working fluid is used to cool or to keep cold
superconductor elements at a temperature of about 65 K, [0030] the
temperature drop of the fluid constituting the cold source is
substantially identical to the temperature rise of the working gas
in the heat exchangers.
[0031] The invention may have one or more of the following
advantages: [0032] the working fluid cycle (reverse Ericsson type)
serves to obtain a higher efficiency than the known systems but
without necessarily creating or increasing other drawbacks, [0033]
the expansion work in the turbines can be advantageously utilized,
[0034] it is possible to eliminate the use of oil for lubrication
or cooling, so as to eliminate the de-oiling installation
downstream of the compressor, and palso the spent oil treatment and
recycling operations, [0035] the system only requires a small
number of moving parts, thereby increasing its simplicity and
reliability. Thanks to the invention, it is possible, for the
compressor, to do without a mechanical power transmission of the
type with speed step-up gear or Cardan joints, etc., [0036]
maintenance operations are reduced or even virtually nonexistent,
[0037] the system serves to avoid rotary seals and to use a
completely hermetically sealed system with regard to the exterior.
This prevents any loss or pollution of the working cycle gas,
[0038] the size of the refrigerator may be reduced in comparison
with known systems.
[0039] Other features and advantages will appear from a reading of
the description below, provided in conjunction with the figures in
which:
[0040] FIG. 1 is a schematic view showing the structure and
operation of a first exemplary embodiment of the refrigeration
device according to the invention,
[0041] FIG. 2 schematically shows a detail of FIG. 1 showing an
arrangement of a drive motor of a compressor-compressor or
compressor-turbine assembly,
[0042] FIG. 3 schematically shows an example of a working cycle of
the working fluid of the refrigerator in FIG. 1,
[0043] FIG. 4 is a schematic view showing the structure and
operation of a second exemplary embodiment of a refrigerator
according to the invention,
[0044] FIG. 5 schematically shows a second example of a working
cycle of the working fluid of the refrigerator in FIG. 3.
[0045] With reference to the exemplary embodiment in FIG. 1, the
refrigerator according to the invention is suitable for
transferring heat from a cold source 15 at a cryogenic temperature
to a hot source at ambient temperature 1 for example.
[0046] The cold source 15 may, for example, be liquid nitrogen for
cooling and the hot source 1 may be water or air. To carry out this
heat transfer, the refrigerator shown in FIG. 1 uses a working
circuit 200 of a working gas comprising the components listed
below.
[0047] The circuit 200 comprises a plurality of centrifugal
compressors 3, 5, 7 disposed in series and operating at ambient
temperature.
[0048] The circuit 200 comprises a plurality of heat exchangers 2,
4, 6 operating at ambient temperature disposed respectively at the
outlet of the compressors 3, 5, 7. The temperatures of the working
gas at the inlet and outlet of each compression stage (that is at
the inlet and outlet of each compressor 3, 5, 7) are kept by the
heat exchangers at a substantially identical level (cf. zone A in
FIG. 3 which shows a gas working cycle: temperature in K as a
function of the entropy S in J/kg). In FIG. 3, the rising portions
of zone A in a sawtooth pattern each correspond to a compression
stage, while the descending portions of this zone A each correspond
to a cooling by heat exchanger.
[0049] This arrangement serves to approach isothermal compression.
The inlet and outlet temperatures of each compression stage are
substantially the same.
[0050] The heat exchangers 2, 4, 6 may be different or may be
composed of distinct portions of the same heat exchanger in heat
exchange with the hot source 1.
[0051] The refrigerator comprises a plurality of high-speed motors
(70 cf. FIG. 2). In the context of the present invention,
high-speed motor normally means motors whereof the speed of
rotation allows a direct coupling with a centrifugal compression
stage or a centripetal expansion stage. The high-speed motors 70
preferably use magnetic or dynamic gas bearings 171 (FIG. 2). A
high-speed motor typically rotates at a speed of 10 000 rpm or
several tens of thousands of rpm. A low-speed motor rotates at a
speed of a few thousand rpm.
[0052] Downstream of the compression portion comprising the
compressors in series, the refrigerator comprises a heat exchanger
8 preferably of the countercurrent plate type separating the
elements at ambient temperature (in the upper part of the circuit
200 shown in FIG. 1) from the elements at cryogenic temperature (in
the lower part of the circuit 200). The fluid is cooled
(corresponding to zone D in FIG. 3). The cooling of the gas from
ambient temperature to cryogenic temperature takes place by
countercurrent exchange with the same working gas at cryogenic
temperature, which originates from the expansion portion after heat
exchange with the cold source 15.
[0053] Downstream of this cooling portion comprising the plate heat
exchanger 8, the circuit comprises one or more expansion turbines
9, 11, 13, preferably of the centripetal type, disposed in series.
The turbines 9, 11, 13 operate at cryogenic temperature, the inlet
and outlet temperatures of each expansion stage (turbine inlet and
outlet) are kept substantially identical by one or more cryogenic
heat exchangers 10, 12, 14 disposed at the outlet of the
turbine(s). This corresponds to zone C in FIG. 3, the descending
portions of zone C each corresponding to an expansion stage while
the rising portions of this zone correspond to the heating in the
heat exchangers 10, 12, 14. This arrangement serves to approach an
isothermal expansion. The inlet and outlet temperatures of each
expansion stage are substantially the same. Moreover, and in order
to increase the efficiency of the refrigerator, the increase in the
working gas temperature in the heat exchanger(s) (10, 12, 14) may
be substantially identical (in absolute value) to the drop in the
temperature of the fluid to be cooled (15) (cold source).
[0054] These heating heat exchangers 10, 12, 14 may be different or
may be composed of distinct portions of the same heat exchanger
exchanging heat with the cold source 15.
[0055] Downstream of the expansion and heat exchange portion with
the cold source 15, the working fluid again exchanges heat with the
plate heat exchanger 8 (zone B in FIG. 3). The fluid exchanges heat
in the heat exchanger 8 in countercurrent to its passage after the
compression portion. After heating, the fluid returns to the
compression portion and can repeat its cycle.
[0056] The circuit may further comprise a chamber of working gas at
ambient temperature (not shown for the sake of simplification) to
limit the pressure in the circuits, during the shutdown of the
refrigerator for example.
[0057] The refrigerator preferably uses as working fluid a fluid in
the gas phase flowing in a closed circuit. This is composed for
example of a pure gas or a mixture of pure gases. The most suitable
gases for this technology are in particular: helium, neon,
nitrogen, oxygen and argon. Carbon monoxide and methane may also be
used.
[0058] The refrigerator is designed and thus operated so as to
obtain a fluid working cycle approaching the reverse Ericsson
cycle. This means: an isothermal compression, an isobaric cooling,
an isothermal expansion and an isobaric heating.
[0059] According to an advantageous feature, in order to drive at
least the compressors 3, 5, 7 (that is to drive the compressor
impellers), the refrigerator uses a plurality of high-speed motors
70.
[0060] As shown schematically in FIG. 2, each high-speed motor 70
accommodates a compressor impeller 31 on one end of its output
shaft and, on the other end of its output shaft, another compressor
impeller or a turbine wheel 9. This arrangement provides many
advantages. This configuration allows a direct coupling in the
refrigerator between the motor 70 and the impellers of the
compressor 3, 5, 7 or between the motor 70 and the wheels of the
turbines 9, 11, 13. This serves to do without a speed step-up gear
or reducer (thereby limiting the number of moving parts required).
This configuration also allows the utilization of the mechanical
work of the turbine(s) 9, 11, 13 and in consequence, an increase in
the total energy efficiency of the refrigerator. According to this
configuration, the refrigerator operates without oil, thereby
guaranteeing the purity of the working gas and eliminating the need
for a de-oiling operation.
[0061] The number of high-speed motors mainly depends on the energy
efficiency desired for the refrigerator. The higher this
efficiency, the higher the number of high-speed motors.
[0062] The ratio between the number of compression stages
(compressors) and the number of expansion stages (turbines) depends
on the target cold temperature. For example, for a refrigerator of
which the cold source is at 273 K, the number of compression stages
is substantially equal to the number of expansion stages. For a
refrigerator in which the cold source is at 65 K, the number of
compression stages is about 3 times higher than the number of
expansion stages.
[0063] FIG. 4 shows another embodiment which can be used for
example to cool or maintain the temperature of superconductor
cables at a cryogenic temperature of about 65 K. For this
temperature level, the number of compression stages (compressors)
must be about three times higher than the number of expansion
stages (turbines). This can be obtained in several possible
configurations. For example, three compressors and one turbine or
six compressors and two turbines.
[0064] The choice of the number of units depends on the desired
energy efficiency. Thus, a solution using three compressors and one
turbine will have a lower energy efficiency than a solution using
six compressors and two turbines.
[0065] In the example in FIG. 4, the refrigerator comprises six
compressors 101, 102, 103, 104, 105, 106 and two turbines 116, 111
and four high-speed motors 107, 112, 114, 109. The first two
compressors 101, 102 (that is the compressor impellers) are mounted
respectively at the two ends of a first high-speed motor 107. The
next two compressors 103, 104 are mounted respectively on the two
ends of a second high-speed motor 112. The next compressor 105 and
the turbine 116 (that is the turbine wheel) are mounted
respectively on the two ends of a third high-speed motor 114.
Finally, the last turbine 111 and the sixth compressor 106 are
mounted respectively on the two ends of a fourth motor 109.
[0066] The routing of the working gas during a cycle in the closed
loop circuit can be described as follows.
[0067] In a first step, the gas is progressively compressed by
passing in succession through the four compressors in series 101,
102, 103, 104, 105, 106.
[0068] On completion of each compression stage (at the outlet of
each compressor) the working gas is cooled in a respective heat
exchanger 108 (by heat exchange with air or water for example) to
approach isothermal compression. After this compression portion,
the gas is isobarically cooled through a countercurrent plate heat
exchanger 103. After this cooling portion, the cooling gas is
progressively expanded in the two centripetal turbines in series
116, 111. After each expansion stage the working gas is heated by
heat exchange in a heat exchanger 110 (for example by heat exchange
with the cold source), in order to obtain a substantially
isothermal expansion. On completion of this isothermal expansion,
the working gas is heated in the heat exchanges 113 and can then
start a new cycle by a compression.
[0069] FIG. 5 shows the cycle (temperature T and entropy S) of the
working fluid of the refrigerator in FIG. 5. As previously for FIG.
3, six sawteeth can be distinguished in the compression zone A,
corresponding to the six successive compressions and coolings. In
the expansion zone C, two sawteeth are identified, corresponding to
the two successive expansions and heatings.
[0070] The invention improves the cryogenic refrigerators in terms
of energy efficiency, reliability and size. The invention serves to
decrease the number of maintenance operations and to eliminate the
use of oils.
[0071] Obviously, one or both ends of the output shafts of the
motor(s) can directly drive more than one wheel (that is a
plurality of compressors or a plurality of turbines).
* * * * *