Note: Descriptions are shown in the official language in which they were submitted.
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THER1VIOSYPHON CONFIGURATION FOR CASCADE REFRIGERATION
SYSTEMS
RELATED APPLICATIONS
[0101] The present application is a non-provisional application claim priority
to
U.S. Provisional Application Serial No. 62/114,603, filed on February 11,
2105. U.S.
Provisional Application Serial No. 62/114,603 is incorporated by reference
herein in full.
TECHNICAL FIELD
[0102] The present application and the resultant patent relate generally to
refrigeration systems and more particularly relate to a cascade refrigeration
system using
a thermosyphon in communication with a cascade evaporator-condenser the low
side
cooling cycle components.
BACKGROUND OF THE INVENTION
[0103] Cascade refrigeration systems generally include a first side cooling
cycle,
or a high side cooling cycle, and a second side cooling cycle, or a low side
cooling cycle.
The two cooling cycles interface through a common heat exchanger, i.e., a
cascade
evaporator-condenser. The cascade refrigeration system may provide cooling at
very low
temperatures in a highly efficient manner.
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[0104] Current refrigeration trends promote the use of ammonia, carbon
dioxide,
and other types of natural refrigerants instead of conventional
hydrofluorocarbon based
refrigerants. Cascade refrigeration systems may use ammonia in the high cycle
and
carbon dioxide in the low cycle. Moreover, there is an interest in improving
the overall
efficiency of such natural refrigerant based refrigeration systems at least as
compared to
the conventional hydrofluorocarbon based systems.
[0105] There is thus a desire for an improved refrigeration system such as a
cascade refrigeration system that provides cooling with increased efficiency
with natural
or any type of refrigerants. Such an improved refrigeration system may
accommodate the
high pressures needed for low temperature cascade cooling in an efficient,
reliable, and
safe manner.
SUMMARY OF THE INVENTION
[0106] The present application and the resultant patent thus provide a
thermosyphon for use with a refrigeration system. The thermosyphon may include
a
primary flow inlet, an angled secondary flow inlet, and a mixed flow outlet.
The angled
secondary flow inlet may include an angle 01 of about forty-five degrees or
less with
respect to the mixed flow outlet_ The angled flow may improve the mass flow
rate or
reduce the pressure of the primary inlet flow and the mixed outlet flow as
compared to a
perpendicular orientation.
101071 The present application and the resultant patent further provide a
method
of improving a mass flow rate or reducing a pressure loss of a refrigerant to
a cascade
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evaporator-condenser. The method may include the steps of providing a
thermosyphon
with an outlet in communication with the cascade evaporator-condenser,
providing a
primary refrigerant flow from a first source, providing a secondary
refrigerant flow from
a second source, mixing the primary refrigerant flow and the secondary
refrigerant flow
at an angle less than about ninety degrees, and providing the mixed
refrigerant flow to the
cascade evaporator-condenser via the thermosyphon outlet.
[0108] The present application and the resultant patent further provide a
thermosyphon for use with a refrigeration system. The thermosyphon may include
a tank
inlet in communication with a liquid vapor separator tank, an angled
compressor inlet in
communication with one or more compressors, and a cascade outlet in
communication
with a cascade evaporator-condenser. The angled compressor inlet may include
an angle
01 of about forty-five degrees or less with respect to the cascade outlet.
[0109] These and other features and improvements of the present application
and
the resultant patent will become apparent to one of ordinary skill in the art
upon review of
the following detailed description when taken in conjunction with the several
drawings
and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0110] Fig. 1 is a schematic diagram of a known cascade refrigeration system
with a high side cycle and a low side cycle.
[0111] Fig. 2 is a schematic diagram of a thermosyphon configuration as used
in a
known cascade refrigeration system.
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[0112] Fig. 3 is an alternative embodiment of a known thermosyphon
configuration.
[01131 Fig. 4 is a thermosyphon configuration as may be described herein with
an
improved mass flow rate or reduced pressure loss.
[0114] Fig. 5 is an alternative embodiment of a thermosyphon configuration as
may be described herein.
10115] Fig. 6 is an alternative embodiment of a thermosyphon configuration as
may be described herein.
DETAILED DESCRIPTION
[0116] Referring now to the drawings, in which like numerals refer to like
elements throughout the several views, Fig. I shows an example of a cascade
refrigeration system 100. The cascade refrigeration system 100 may be used to
cool any
type of enclosure for use in, for example, supermarkets, cold storage, and the
like. The
cascade refrigeration system 100 also may be applicable to other types of
heating,
ventilation, and air conditioning applications and/or different types of
commercial and/or
industrial applications. The overall cascade refrigeration system 100 may have
any
suitable size or capacity. Other types of refrigeration systems, cycled, and
components
also may be used herein.
[0117] Generally described, the cascade refrigeration system 100 may include a
first or a high side cycle 110 and a second or a low side cycle 120, The high
side cycle
110 may include one or more high side compressors 130, a high side oil
separator 140, a
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high side condenser 150, a high side receiver 160, and a high side expansion
device 170.
The high side cycle 110 also may include a suction/liquid heat exchanger 180
and a
suction accumulator 190. The high side cycle 110 may include a flow of a
refrigerant
200. The refrigerant 200 may include a flow of ammonia or other type of a
refrigerant.
The high side cycle 110 components may have any suitable size, shape,
configuration, or
capacity. The high side cycle 110 may use other and additional components and
configurations herein.
[0118] The low side cycle 120 similarly may include one or more low side
compressors 210, a low side oil separator 220, a low side liquid vapor
separator tank 230,
one or more low side expansion devices 240, and one or more low side
evaporators 250.
The low side cycle 120 may include a medium temperature loop 260 with a pump
270
and a number of flow valves 280 as well as a low temperature loop 290. An
accumulator
300 also may be used therein. The low side cycle 120 may include a flow of a
refrigerant
310. The refrigerant 310 may include a flow of carbon dioxide or other type of
a
refrigerant. The low side cycle 120 components may have any suitable size,
shape,
configuration, or capacity. The low side cycle 120 may use other and
additional
components and configurations herein.
[0119] The two cycles 110, 120 may interface through a cascade
evaporator/condenser 320. The respective flows of the refrigerants 200, 310
may
exchange heat via the cascade evaporator/condenser 320. The
cascade
evaporator/condenser 320 may have any suitable size shape, configuration, or
capacity.
Other components and other configurations may be used herein.
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[0120] The refrigerant 200 may be compressed by the high side compressors 130
and condensed in the high side condenser 150. The refrigerant 200 may be
stored in the
high side receiver 160 and may be withdrawn as needed to satisfy the load on
the cascade
evaporator/condenser 320. The refrigerant 200 then may pass through the
suction/liquid
heat exchanger 180, the high side expansion device 170 and the cascade
evaporator/condenser 320. The refrigerant 200 again passes through the
suction/liquid
heat exchanger 180 and returns to the high side compressors 130. The
suction/liquid heat
exchanger 180 may be used to sub-cool the refrigerant 200 before entry into
the cascade
evaporator/condenser 320. Other components and other configurations may be
used
herein.
[0121] The low side cycle 120 may be similar. The carbon dioxide based
refrigerant 310 may be compressed by the low side compressors 210 and then
pass
through the cascade evaporator/condenser 320. The refrigerant 310 may be
stored within
the low side liquid vapor separator tank 230 and withdrawn as needed. The
refrigerant
310 may pass through one or more low side expansion devices 240 and one or
more low
side evaporators 250. The low side cycle 120 may be separated into the low
temperature
loop 290 and the medium temperature loop 260. Other components and other
configurations may be used herein.
[0122] The low side cycle 120 also may use a thermosyphon 330. The
thermosyphon 330 provides for the circulation of a fluid, in this case the
refrigerant 310,
based upon thermal gradients as opposed to mechanical devices such as a pump
and the
like. In this example, the thermosyphon 330 may have a tank inlet 340 in
communication
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with the low side liquid vapor separator tank 230, a compressor inlet 350 in
communication with the low side compressors 210, and a cascade outlet 360 in
communication with the cascade evaporator-condenser 320.
[0123] In use, the liquid/gas flow of the carbon dioxide refrigerant 310 may
be
diverted to the low side liquid vapor separator tank 230 where the liquid and
vapor may
separate therein. The vapor portion may be routed to the cascade evaporator-
condenser
320 through the thermosyphon 330 and mixed with the vapor exiting the low side
compressors 210 so as to condense the vapor to a liquid. Other components and
other
configurations may be used herein.
[0124] Figs. 1 and 2 show an example of a conventional configuration of the
therrnosyphon 330. The compressor inlet 350 may be in line with the cascade
outlet 360.
The tank inlet 340 may merge in a perpendicular relationship at approximately
a ninety
degree (90 ) angle so as to provide the thermosyphon 330 with a substantial
tank "T" like
shape 370. Fig. 3 shows a similar configuration in which the tank inlet 340 is
in line with
the cascade outlet 360 and the compressor inlet 350 merges perpendicularly for
a
compressor "T" like shape 380. In either orientation, the flows merge at about
the
perpendicular angle.
[0125] The flow from the low side liquid vapor separator tank 230 through the
tank inlet 340 may be considered a primary flow 390. The flow from the
compressors
210 to the compressor inlet 350 may be considered a secondary flow 400. Given
the use
of the perpendicular configuration, blocking the respective flows through the
pressure
drop sensitive thermosyphon 330 may be an operational and an efficiency issue.
In a
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conventional cascade system, the primary flow 390 through the tank inlet 340
may be at
about 435.07 psia (about 3000 kpa) with a temperature of about 22 degrees
Fahrenheit
(about -5.5 degrees Celsius) and with a mass flow rate of about 0.17 or 0.18
kg/s. The
secondary flow 400 through the compressor 360 may be at about 145 degrees
Fahrenheit
(about 63 degrees Celsius) and with a mass flow rate of about 0.09 kg/s. After
merging, a
mixed outlet flow 410 at the cascade outlet 360 may be at about 434.87 psia
(about 2998
kpa), about 45 degrees Fahrenheit (about 7.2 degrees Celsius), and with a mass
flow rate
of about 0.26 or 0.27 kg/s. Other pressures, temperatures, mass flow rates,
and other
parameters may be used herein,
[0126] Fig. 4 shows an example of a thermosyphon 420 as may be described
herein. The therrnosyphon 420 may have a tank inlet 430 that is in line with a
cascade
outlet 440. Instead of the compressor inlet 350 merging into the tank inlet
340 in the
perpendicular orientation described above, the therrnosyphon 420 may include
an angled
inlet compressor 450. The angled compressor inlet 450 may be positioned at an
angle 01
with respect to the tank inlet 430 or the centerline of the cascade outlet
440. The angle
01 preferably may range from about more than about zero degrees (0 ) to about
forty-five
degrees (450) or so. Other angles may be used herein. Other components and
other
configurations may be used herein.
[0127] Fig. 5 shows a further example of a thertnosyphon 460 as may be
described herein. In this example, the thermosyphon 460 may include an angled
tank
inlet 470 and/or an angled compressor inlet 480. The inlets 470, 480 then may
merge
into a cascade outlet 490 for a substantial "Y" like shape. The angled tank
inlet 470 may
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be positioned at an angle of 02 with respect to the centerline of the cascade
outlet 490.
The angle 02 preferably may range from about more than about zero degrees (00)
to
about forty-five degrees (450) or so. Other angles may be used herein. The
angled
compressor inlet 480 also may use the angle 01 similar to that described
above.
Specifically, the angles 01 and 02 may be the same or different, Other
components and
other configurations also may be used herein.
[0128] The following chart shows the mass flow rate changes with respect to
the
thermosyphon 330 of Figs. 2 and 3 and the thermosyphons 420, 460 of Figs. 4
and 5.
The comparison assumes the same pressure and temperature at the tank inlet,
the same
mass flow rate and temperature at the compressor inlet, and the same pressure
and
temperature at the cascade outlet. The mass flow rate into the tank inlet and
out of the
cascade outlet will vary. With respect to the angled compressor inlet 450 in
the
thermosyphon 420 of Fig. 4, the angle 01 was varied from six degrees (6 ) to
about
ninety degrees (90 ). Likewise, with respect to the angled tank inlet 470 and
the angled
compressor inlet 480 of the thermosyphon 460, angle 01 varied from about ten
degrees
(10 ) to about thirty degrees (30 ) and 02 varied from about three degrees
(30) to about
thirty degrees (30 ). The respective changes in mass flow rate thus are shown
with
respect to kilograms per second.
Fig. Angle Compressor Tank inlet Cascade Percent
01 inlet (kg/s) (kg/s) outlet
(kg/s) change from
01-02 Fig, 2
2 _ _____________ 0.09 0_17 0.26
3 0.09 0.18 0.27 5.46_
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4 60 0.09 0.24 0.33 41.17
11 0.09 0.24 0.33 41.17
,
15 0.09
0.23 0.32 35.29
30 -0.09 0.23 0.32 35.29
45 0.09 0.23 0.32 35,29
90 0.09 0.09 0.18 -47.03
10 -10 0.09 0.22 0.31 29.70
45 0.09 0.20 0.29 18.29
30 -30 0.09 0.21 0.30 22.79
14 -3 0-09 0.22 0.31 32.34
10129] The tank inlet flow rate and the cascade outlet flow rate thus varied
and
improved with respect to the perpendicular configuration of Figs. 2 and 3. The
use of an
angle of about six degrees (6 ) to about eleven degrees (11 ) improved the
mass flow rate
at the cascade outlet from about 0.26 kg/s to about 0.33 kg/3 or an increase
of about
forty-one percent (41%). Varying the angle of the secondary flow 400 with
respect to the
primary flow 390 thus provides an enhanced primary flow rate as compared to
the
perpendicular angle arrangement and/or a decreased pressure drop along the
primary flow
for the same inlet velocity.
[0130] Fig. 6 shows a further embodiment of a thermosyphon 500 as may be
described herein. In this example, the thermosyphon 500 may include a tank
inlet 510
and an inline cascade outlet 520. In this example, the therrnosyphon 500 may
include an
angled compressor inlet 530. The angle 0/ of the angled compressor inlet 530
thus may
vary. The angled compressor inlet 530 may have a variable diameter 540.
Likewise, the
diameter of the variable diameter 540 may vary. Varying angles and diameters
also may
be used for the tank inlet 510. The tank inlet 510 may have a diameter of
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inches (about 34.9 millimeters) or so. Other components and other
configurations may
be used herein.
[0131] The following chart shows examples in varying the angle 01 as well as
the
diameter from about 0,4 inch (about 10.2 -millimeters) to about one (1) inch
(about 25.4
millimeters) given the constant tank inlet 510 described above.
Fig. Angle 01 Diameter Compressor Tank inlet Cascade Percent
(mm) inlet (kg/s) (kWs) Outlet change
(kg/s) from Fig.
2
6 30 101 0.09 0..35 0.44 106.89
30 15.2 0.09 0.27 0.36 56.44
30 20.3 0.09 0.22 0.31 31.27
30 25.4 0.09 0.22 0.31 27.61
1 I 19.1 0.09 0.24 0.33 , 38.86
101321 The use of a variable diameter 540 of about 10.2 millimeters with an
angle
91 of about thirty degrees for the angled compressor inlet 530 thus results in
more than a
100% improvement over the Fig. 2 baseline. Specifically, a higher secondary
flow from
the compressors 210 may draw more of the refrigerant 310 from the liquid vapor
separator tank 230 without obstructing the flow given a jet of a smaller
diameter.
Likewise, the ratio of the diameters between the angled compressor inlet 530
and the tank
inlet varied from about 0.7 to about 0.3 with at least a 0.5 ratio being
preferred.
[0133] The variable diameter 540 also may be dynamically set depending upon
operational parameters. For example, the variable diameter 540 may vary
depending
upon the load on the overall system and the like. Other parameters may be
considered
herein, Although the thermosyphons herein have been focused on the use of the
carbon
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dioxide refrigerant 310, the thermosyphons described herein may be used to
merge any
type of primary and secondary flows.
[01341 It should be apparent that the foregoing relates only to certain
embodiments of the present application and the resultant patent. Numerous
changes and
modifications may be made herein by one of ordinary skill in the art without
departing
from the general spirit and scope of the invention as defined by the following
claims and
the equivalents thereof.
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