Note: Descriptions are shown in the official language in which they were submitted.
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CARBON DIOXIDE BASED AUXILIARY COOLING SYSTEM
TECHNICAL FIELD
[0101] The present application and the resultant patent relate generally to
refrigeration systems and more particularly relate to a carbon dioxide based
auxiliary
cooling system for a refrigeration system that may be free of the use of
hydrofluorocarbons and the like.
BACKGROUND OF THE INVENTION
[0102] Cascade refrigeration systems generally include a first side cooling
cycle, or a high side 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.
[0103] Current refrigeration trends promote the use of carbon dioxide and
other types of natural refrigerants as opposed to conventional
hydrofluorocarbon
based refrigerants. Unlike hydrofluorocarbons, however, carbon dioxide based
systems may lose refrigerant during power outages. In the case of a power
outage, the
carbon dioxide based system may start gaining heat such that the refrigerant
pressure
may rise and exceed the design pressure of the overall refrigeration system.
The
refrigeration system generally must be vented to the atmosphere in such a
situation.
[0104] In order to avoid venting the refrigerant, carbon dioxide based
refrigeration systems may include a backup condensing unit with an independent
power source to keep the carbon dioxide cool. These known backup devices,
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however, generally use hydrofluorocarbon based refrigerants such that the
refrigeration system as a whole cannot be considered truly "green" or
hydrofluorocarbon free.
[0105] There is thus a desire for a refrigeration system such as cascade
refrigeration systems that provide auxiliary cooling without the use of
hydrofluorocarbons. Such an auxiliary cooling system would provide efficient
cooling in a truly hydrofluorocarbon free design.
SUMMARY OF THE INVENTION
[0106] The present application and the resultant patent thus provide a cascade
refrigeration system. The cascade refrigeration system may include a first
side cycle,
a second side cycle with a second side cycle carbon dioxide refrigerant, and
an
auxiliary cooling system to cool the second side cycle carbon dioxide
refrigerant in
the event of a power outage. The auxiliary cooling system may include an
auxiliary
carbon dioxide refrigerant.
[0107] The present application and the resultant patent further provide a
method of providing auxiliary cooling in a refrigeration system. The method
may
include the steps of flowing a natural refrigerant through a first side cycle,
flowing a
carbon dioxide refrigerant through a second side cycle, providing an auxiliary
cooling
system to cool the flow of the carbon dioxide refrigerant in the case of a
power loss,
and flowing an auxiliary carbon dioxide refrigerant through the auxiliary
cooling
system.
[0108] The present application and the resulting patent further provide a
carbon dioxide based refrigeration system. The carbon dioxide based
refrigeration
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system may include a receiver, a carbon dioxide refrigerant, and an auxiliary
cooling
system in communication with the receiver to cool the carbon dioxide
refrigerant in
the event of a power outage. The auxiliary cooling system may include an
auxiliary
carbon dioxide refrigerant.
[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 cascade refrigeration system with a
carbon dioxide base auxiliary cooling system as may be described herein.
[0112] Fig. 3 is a schematic diagram of an alternative embodiment of a carbon
dioxide based auxiliary cooling system as may be described herein.
DETAILED DESCRIPTION
[0113] Referring now to the drawings, in which like numerals refer to like
elements throughout the several views, Fig. 1 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 heating,
ventilation,
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and air conditioning and/or different types of industrial applications. The
overall
cascade refrigeration system 100 may have any suitable size or capacity.
[0114] 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 a high side compressor 130, a high side oil separator
140, a
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
natural refrigerant 200. The natural refrigerant 200 may include a flow of
ammonia, a
flow of hydrocarbons, and the like. Other components and other configurations
may
be used herein.
[0115] The low side cycle 120 similarly may include a low side compressor
210, a low side oil separator 220, a low side receiver 230, a low side
expansion device
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 carbon dioxide based
refrigerant 310
and the like. Other components and other configurations may be used herein.
[0116] 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 or capacity. Other
components
and other configurations may be used herein.
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[0117] The natural refrigerant 200 may be compressed by the high side
compressor 210 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 high side expansion device 170 and returns to the high
side
compressor 130. The suction/liquid heat exchanger 180 may be used to sub-cool
the
refrigerant 200 before entry into the cascade evaporator/condenser 320.
[0118] The low side cycle 120 may be similar. The carbon dioxide based
refrigerant 310 may be compressed by the low side compressor 210 and then pass
through the cascade evaporator/condenser 320. The refrigerant 310 may be
stored
within the low side receiver 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.
[0119] The cascade refrigeration system 100 also may include an auxiliary
cooling system 330. The cooling auxiliary system 330 may be used to cool the
flow
of the carbon dioxide refrigerant 310 via an interface with the low side
receiver 230 or
elsewhere. The auxiliary cooling system 330 may include an auxiliary
compressor
340, an auxiliary condenser 350, and an auxiliary expansion device. The
cooling
auxiliary system 330 may include a generator 370 or other type of independent
power
supply. The auxiliary cooling system 330 may interface with the low side cycle
120
via an auxiliary condenser/evaporator 380. Known auxiliary cooling systems 330
generally use a hydrofluorocarbon based refrigerant 390 such as R404A or
R407A.
Other components and other configurations may be used herein.
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[0120] Fig. 2 shows a cascade refrigeration system 400 as may be described
herein. The cascade refrigeration system 400 may include the same or a similar
high
side cycle 110 and low side cycle 120. The two cycles may interface via the
cascade
evaporator/condenser 320 and the like. As described above, the low side cycle
120
includes the flow of the carbon dioxide based refrigerant 310.
101211 The cascade refrigeration system 400 also may include a carbon
dioxide based auxiliary cooling system 410. The carbon dioxide auxiliary
cooling
system 410 may include an auxiliary compressor 420, an auxiliary condenser
430, and
an auxiliary expansion device 440. The carbon dioxide auxiliary cooling system
410
may include an auxiliary generator 450 or other type of independent power
supply.
The carbon dioxide auxiliary cooling system 410 may interface with the low
side
cycle 120 via an auxiliary condenser/evaporator 460 or other type of heat
exchange
device. The carbon dioxide auxiliary cooling system 410 may include a flow of
a
carbon dioxide based refrigerant 470 therein. Other types of natural
refrigerants also
may be used herein. Other components and other configurations may be used
herein.
101221 In the event of the loss of power, the carbon dioxide auxiliary cooling
system 410 may be used to cool the flow of the carbon dioxide refrigerant 310
in the
low side cycle 120 via the carbon dioxide refrigerant 470 circulating therein
and
interfacing at the auxiliary condenser/evaporator 460. The cascade
refrigeration
system 400 thus is truly a hydrofluorocarbon free system. The carbon dioxide
based
auxiliary cooling system 410 may provide a faster overall response time in a
proactive
method of cooling the flow of carbon dioxide refrigerant 310 without venting.
Multiple carbon dioxide auxiliary cooling systems 410 may be used herein.
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[0123] Fig. 3 shows an alternative embodiment of a carbon dioxide auxiliary
cooling system 500 as may be described herein. The carbon dioxide auxiliary
cooling
system 500 may include an auxiliary compressor 510, an auxiliary gas cooler
520 or
condenser, and an auxiliary expansion device 530. The carbon dioxide auxiliary
cooling system 500 also may include an auxiliary generator or other type of
independent power source. The carbon dioxide auxiliary cooling system 500 also
may include a flow of a carbon dioxide based refrigerant 540 therein. Other
components and other configurations may be used herein.
[0124] The carbon dioxide auxiliary system 500 may tie directly into the low
side cycle 120 via the low side cycle receiver 230 for heat exchange
therewith. The
carbon dioxide auxiliary system 500 thus avoids the need for an auxiliary
condenser/evaporator and/or pump in a truly a hydrofluorocarbon free system.
The
carbon dioxide based auxiliary system 500 also may provide a faster overall
response
time in a proactive method of cooling the flow of carbon dioxide refrigerant
310
without venting.
[0125] Although the carbon dioxide based auxiliary cooling systems have
been shown in the context of a cascade refrigeration system, the carbon
dioxide based
auxiliary cooling systems may be used in any type of carbon dioxide
refrigeration
system. Specifically, any type of carbon dioxide refrigeration system using a
large
receiver tank and the like.
[0126] 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
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departing from the general spirit and scope of the invention as defined by the
following claims and the equivalents thereof.
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