Note: Descriptions are shown in the official language in which they were submitted.
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REFRIGERATION SYSTEM WITH MODULATED CONDENSING LOOPS
FIELD OF THE INVENTION
(00017 The present invention generally relates. to
refrigeration systems, and more particularly, to modulate
closed condensing loops for use therewith.
BACKGROUND OF THE INVENTION
(00027 In a typical refrigeration system, particularly
those found in supermarkets, a plurality of evaporators are
used to refrigerate foodstuff in refrigerated display cases.
Such systems basically comprise a closed circuit having a
compressor stage, a condenser stage, an expansion stage and
an evaporator stage. Other stages may be added to the above
described basic refrigeration circuit in order to recuperate
heat, or to provide refrigeration systems with defrosting
loops for high speed defrosting of the evaporators. For
instance, U.S. Patent No. 5,673,567, issued on October 7,
1997 to the present assignee, discloses a refrigeration
system with a heat reclaim loop for recuperating heat from
hot high pressure refrigerant gas outletting from the
compressor stage, rather than evacuating the heat through
the condensers, where the heat would be lost to the
atmosphere. Thus, the heat reclaim loop is provided in
parallel to the condenser stage in order to recuperate heat
in heat exchange devices rather than rejecting it to the
atmosphere. Preferably, in the cooler seasons, the heat is
used for heating the entrance area and other specific colder
areas of supermarkets. In the warmer months, the heat may
be recuperated for heating water.
(00037 U.S. Patent No. 5,826,433, issued on October 27,
1998 to the present assignee, discloses modification to the
above described patent, whereby a modulating valve is
provided for efficiently controlling the rate of heat
reclaim versus the heat rejection through the condenser
stage.
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(0004 Finally, U.S. Patent No. 6,089,033, issued on
July 18, 2000 to the present assignee discloses a
refrigeration system configuration in order to defrost
evaporator units at higher speeds.
(00051 These refrigeration systems, and generally most
refrigeration systems used in supermarkets, have roof top
condensers in order to reject heat at the outlet of the
compressor stage, whereby the refrigerant is condensed at
least partially to a liquid state. Unfortunately, the loops
to the roof top condensers extend the piping length of the
refrigeration system. Accordingly, the piping networks of
refrigeration systems are filled with refrigerant to provide
every stage with the necessary conditions for refrigeration.
Furthermore, with the advent of heat reclaim loops and high
speed defrost cycles, even more refrigerant is used.
(ooosl Unfortunately, the refrigerants typically used in
such refrigeration systems (i.e. refrigerants 404, 408, 507,
AZ-20 and the like) are expensive and are often volatile,
whereby they may be hazardous to human health and to the
environment. The more these refrigerants are used, the
higher is the risk of polluting the environment.
SUMMARY OF THE INVENTION
It is a feature of the present invention to
provide a refrigeration systems having reduced amounts of
the above stated refrigerants.
(0008 It is a further feature of the present invention
to provide a refrigeration system optimizing heat reclaim
with respect to compressor operation.
According to the above feature of the present
invention, and from a broad aspect thereof, the present
invention provides a refrigeration system having a main
refrigeration circuit having a condensing stage, wherein a
first refrigerant in a high pressure gas state is condensed
at least partially to a liquid state. The condensing stage
has a pair of stand-alone condensing stage closed loops in
heat exchange relation with the main refrigeration circuit.
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The stand-alone condensing stage closed loops are parallel
one to another and each comprise a second refrigerant
circulating between at least a heat absorption stage,
wherein the second refrigerant absorbs heat from the first
refrigerant in the main refrigeration circuit so as to
condense the first refrigerant to the liquid state, and a
heat release stage, wherein the second refrigerant releases
the absorbed heat. The condensing stage has modulating
valves for selectively and quantitatively modulating the
temperature of said first refrigerant and compressor head
pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the present invention
will now be described in detail having reference to the
accompanying drawings in which:
tooio~ Fig. 1 is a schematic diagram illustrating a
stand-alone evaporative condenser loop of the present
invention;
fooiil Fig. 2 is a schematic diagram depicting a stand-
alone heat reclaim loop of the present invention; and
(ooi2~ Fig. 3 is a schematic diagram illustrating a
refrigeration system having the stand-alone evaporative
condenser loop and heat reclaim loop.
DESCRIPTION OF PREFERRED EMBODIMENTS
fooi3~ Referring to Fig. 1, there is generally shown at
a stand-alone evaporative condenser loop of the present
invention. The loop 10 comprises a plate heat exchanger 12
for the heat exchange between a refrigerant A in a
refrigeration system and a refrigerant B in the evaporative
condenser loop 10. Refrigerant A of the refrigeration system
entering the heat exchanger 12 is from the output of
compressors in a high pressure hot gas state, and goes
through the heat exchanger 12 to release latent heat by
condensing, to then exit therefrom at least partially in a
high pressure liquid state. Thus, a gas refrigerant line
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from the refrigeration system is shown entering the heat
exchanger 12 through inlet line I, whereas a liquid
refrigerant line exits the heat exchanger 12 at outlet
line O. The refrigeration system will be described in
further detail hereinafter.
too141 The condensing loop 10 has an evaporative
condenser 14. The evaporative condenser 14 typically
comprises a coiling system therein, across which a fluid
flows in order for refrigerant within the coiling system to
release heat it has previously absorbed in the heat
exchanger 12. For instance, the fluid may be air or a spray
of water flowing over the coiling system. A condenser
feedline 16 connects the heat exchanger 12 to the
evaporative condenser 14. It is pointed out that the
condensing loop 10 may be provided with a plurality of
evaporative condensers 14, wherefore a branch line 18 is
shown diverging from the condenser feedline 16 to add
similar evaporative condensers 14 in parallel to the first
one. The condenser feedline 16 is provided with valves and
control devices to ensure the flow direction and the proper
refrigerant conditions. For instance, a manometer 20 is
shown mounted in the condenser feedline 16, as well as a
plurality of check valves 22.
foolsl A condenser return line is generally shown at 24
and connects the evaporative condenser 14 to the heat
exchanger 12, so as ensure the flow of cooled refrigerant
from the evaporative condenser 14 to the heat exchanger 12.
A pump 26 is provided in the condenser return line 24 to
ensure the flow of the refrigerant B in the condensing loop
10. A filter 28 in the condenser return line 24 filters out
the refrigerant. Further check valves 22 and manometer 20
are provided in the condenser return line 24. Furthermore,
parallel loops (not shown) along with manually operated
valves (e. g. three-way valves, ball valves, butterfly
valves) may also be provided in order to isolate the various
components of the condensing loop 10 for maintenance or for
servicing purposes. A branch line 30 is shown connecting to
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the condenser return line 24 in the event where more than
one evaporative condenser 14 are part of the condensing
loop 10.
tools) Referring now to Fig . 2 , a stand-alone heat
reclaim loop in accordance with the present invention is
generally shown at 50. The heat reclaim loop 50 comprises a
plate heat exchanger 52, provided for absorbing heat from a
refrigerant A in a refrigeration system. The refrigerant A
in the refrigeration system is in a high pressure hot gas
state when entering the heat exchanger 52 and is condensed
to a liquid state to then exit the heat exchanger 52. The
inlet line of hot pressure gas refrigerant A is shown at I2,
whereas the outlet of condensed liquid refrigerant A is
shown at outlet line 02.
fool) The heat reclaim loop 50 has a heat reclaim coil
54 and a air heating unit 56. The heat reclaim coil 54 is
typically installed in a ventilation duct through which air
circulates, so as to warm up the air. The air heating unit
56 is typically provided for heating areas where ventilation
is not required (e.g. shipping dock, entrance). It is
pointed out that the heat reclaim loop 50 may be limited to
either one of the heat reclaim coil 54 and the heating unit
56, or may even have a plurality of both. A heat reclaim
feedline 58 connects the heat exchanger 52 to the heat
reclaim coil 54 and to the air heating unit 56 to ensure the
flow of a refrigerant B therebetween. An accumulation tank
60 is connected in the heat reclaim feedline 58 for
accumulating refrigerant B having absorbed heat in the heat
exchanger 52. A pump 62 is also mounted in the heat reclaim
feedline 58, downstream from the accumulation tank 60 to
ensure the flow of refrigerant B from the accumulation tank
60 to the heat reclaim coil 54 and the air heating unit 56.
A heat reclaim return line 64 connects the heat reclaim coil
54 and the air heating unit 56 to the heat exchanger 52,
thereby ensuring the flow of refrigerant B from the formers
to the latter.
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foolel The heat reclaim coil 54 has an inlet line 66
separated from the heat reclaim feedline 58 by a three-way
valve 68. A by-pass line 70 is connected to the free port
of the three-way valve 68 and converges with an outlet line
72 of the heat reclaim coil 54 to reach the heat reclaim
return line 64. Thus, the three-way valve 68 controls the
flow of refrigerant B from the heat reclaim feedline 58 to
the heat reclaim coil 54. The three-way valve 68 may be
fully closed to the inlet line 66 of the heat reclaim coil
54, whereby refrigerant B flows through the by-pass line 70
to reach the heat reclaim return line 64. It is pointed out
that the outlet line 72 comprises a check valve 74 such that
refrigerant by-passing the heat reclaim coil 54 is prevented
from entering same through the outlet line 72 thereof.
foolsl The air heating unit 56 is connected to the heat
reclaim loop 50 in parallel to the heat reclaim coil 54.
The heating unit 56 has an inlet line 76 connected to the
heat reclaim feedline 58 through a three-way valve 78. The
free port of the three-way valve 78 is connected to a
by-pass line 80 which converges with an outlet line 82 of
the heating unit 56 to connect to the heat reclaim return
line 64. Similarly to the heat reclaim coil 54, the flow of
refrigerant B to the heating unit 56 is controlled by the
three-way valve 78. Once more, the heating unit 56 may be
by-passed by the refrigerant B, whereby refrigerant B
circulates through the by-pass line 80 and is prevented from
entering the heating unit 56 by the check valve 84 mounted
therein.
foo2o~ The pump 62 and the accumulation tank 60 allow
storage of refrigerant B, having absorbed heat in the heat
exchanger 52. If the heat reclaim coil 54 and the air
heating unit 56 are in standby (by being by-passed) as the
demand for heating air is low, the tank 60 accumulates the
heated refrigerant B such that the heat reclaim loop 50 is
able to sustain sudden and rapid increases in demand of
heating air. The pump 62 may stop operating beyond certain
levels of refrigerant B. It is pointed out that the
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accumulation tank 60 may be insulated to keep the
refrigerant therein in given states. The pump 62 may be
automated in order to operate automatically according to
factors such as outdoor and indoor temperatures, as well as
refrigerant B temperature. Increased refrigerant B demand
may thus be anticipated and fulfilled by the pump 62 and the
accumulation tank 60.
foo2l~ The heat reclaim loop 50 comprises various devices
for the control of the refrigerant parameters, such as the
direction of flow, the pressure and the filtering. For
instance, filter 86, check valves 88 and manometers 90 are
provided in the heat reclaim loop 50 for the above described
reasons.
foo22~ Now that both the stand-alone evaporative
condenser loop 10 and heat reclaim loop 50 have been
described in detail, a typical refrigeration system in which
the formers may be used will now be described. Because the
stand-alone condensing loops use non-polluting refrigerants
such as glycol, there is a reduction in the quantity of
refrigerant required in the conventional portion of the
refrigeration system.
X0023) Referring now to Fig. 3, a refrigeration system
100 is typically adapted for receiving the stand-alone
evaporative condenser loop 10 described in Fig. 1 and the
heat reclaim loop 50 described in Fig. 2. The evaporative
loop 10 and the heat reclaim loop 50 are shown connected to
the refrigeration system 100 parallel one to another.
Similarly to the description of the loops 10 and 50, for
clarity purposes, a refrigerant, identified as refrigerant
A, which will be discussed hereinafter, flows in the
refrigeration system 100, whereas a refrigerant, referred to
as refrigerant B, flows in the loops 10 and 50.
Furthermore, as the invention resides in the portion of the
refrigeration system involving the stand-alone evaporative
condenser loop 10 and the stand-alone heat reclaim loop 50,
which have been described extensively above, the
refrigeration system 100 will only be described
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schematically. For instance, the refrigeration system 100
shown in Fig. 3 comprises high speed defrost loops which
will not be described herein.
(00247 As shown in Fig. 3, the refrigeration system 100
comprises a plurality of compressors 102. Refrigerant A
from compressors 102 is in a high pressure gas state. A
header.106 and a high pressure gas line 108 are connected to
the outlets of the compressors 102 so as to convey the high
pressure gas refrigerant A exiting therefrom to a three-way
control valve 104 and modulating valves 105 and 107, which
separates the high pressure gas line 108 into an evaporative
condenser line 110 and a heat reclaim line 112. Both the
evaporative condenser line 110 and the heat reclaim line 112
will converge to a liquid refrigerant reservoir 114, after
having high pressure gas refrigerant A gone through heat
exchangers 12 and 52 of the evaporator condenser loop 10 and
the heat reclaim loop 50, respectively. Therefore, as the
evaporative condenser line 110 and the heat reclaim line 112
diverge at the valves 104, 105 and 107 and converge at the
refrigeration reservoir 114, these lines are parallel one to
another. It is pointed out that the evaporative condenser
line 112 was referred to as input line I and output line O
in Fig. 1, wherefore reference letters I and O have been
added to Fig. 3. Similarly, the heat reclaim line 112 was
referred to in Fig. 2 as inlet line I2 and outlet line 02,
wherefore reference letters for the latters have been added
to Fig. 3.
foo257 The three-way control valve 104 and the modulating
valves 105 and 107 are adapted to control the amounts of
refrigerant A flowing to the evaporative condenser line 110
and the heat reclaim line 112. A main objective of the
refrigeration system 100 is to recuperate as much heat as
possible from the refrigerant A requiring to be condensed at
least partially to a liquid state. However, in order to
keep the operation costs low for such a refrigeration
system, the compressor 102 must operate with the head
pressures as low as possible, yet by fulfilling the
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compression needs of the system. By the use of parallel
condenser line 110 and heat reclaim line 112, it is possible
to optimize the head pressure of the refrigerant A in the
main refrigeration system 100. According to a plurality of
factors which will be described hereinafter, the three-way
control valve 104 and the modulating valves 105 and 207 can
completely shut the feeding of high pressure gas refrigerant
A to either one of the heat exchanger 12 and heat exchanger
52, as well as modulate and control the output pressure of
the compressor 102. As mentioned in the description of the
evaporative condenser loop 10 and the heat reclaim loop 50,
the high pressure gas refrigerant A exiting the heat
exchangers 12 and 52, respectively, through outlet lines O
and 02, is in a high pressure liquid state.
(0026 Typically, the head pressure in the condenser line
110 floats in order to maintain the pressure of refrigerant
A in this portion of the refrigeration system at a
relatively low pressure. As the evaporative condenser loop
has great cooling capacities due to the use of water to
cool refrigerant B, which then cools refrigerant A through
heat exchanger 12, the condenser line 110 allows lowering of
the output refrigerant A pressure of the compressors 102,
thereby resulting in energy savings. Modulating valves 105
and 107 modulate the output pressure of the compressors 102.
One, for instance, may operate at lower pressures, whereas
the other works at higher pressures. The pressure of
refrigerant A varies according to a few factors. The
compressors must operate as little as possible, as they
increasingly consume electricity as a function of their
pressure output. On the other hand, the refrigerant
released from the compressors 102 must be at a temperature
above that of the cooling fluid, usually a predetermined
constant pressure differential (e.g., +15°C). In the
present invention, the cooling fluid is refrigerant B, which
is actually cooled by the ventilation air in the heat
reclaim coil 54 or the heating unit 56 in the case of the
heat reclaim line 112, and by water in the evaporative
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condenser 14 in the case of the evaporative condenser line
10. Therefore, the temperature and pressure of the
refrigerant A are modulated in accordance with the heat
reclaim demand, the indoor air temperature and the outdoor
air temperature.
foo2~~ Thereafter, high pressure liquid refrigerant A
accumulated in the liquid refrigerant reservoir 114 flows
through a liquid refrigerant line 116 and liquid refrigerant
header 118 to reach the expansion valves 120 of the
refrigeration system 100. High pressure liquid refrigerant
A flowing across the expansion valves 120 expands to be
lowered in pressure. Therefore, refrigerant A, in a low
pressure liquid state, flows to evaporators 122 through
evaporator inlet lines 124, which extend between the
expansion valves 120 and the evaporators 122. The low
pressure liquid A is at a temperature well below the desired
temperature of the refrigerator units (not shown). The
refrigerant A absorbs heat in the evaporators 122, whereby
it exits the evaporators 122 in a gas state. The low
pressure liquid refrigerant A exits the evaporators 122 in
evaporator outlet lines 126 to reach a suction header 128 to
then return to the compressors 102.
foo28~ Typical refrigerants used as refrigerant A are
refrigerants 404, 408, 507, AZ-20. The typical refrigerants
used as refrigerant A may be volatile, whereby they are a
threat to the environment as they evaporate at ambient
conditions. Furthermore, they are toxic and are likely
hazardous to health. The evaporative condenser loop 10 and
the heat reclaim loop 50 allow for the reduction of size of
the refrigeration system 100. Typically, the evaporative
condenser line 110 and the heat reclaim line 112 extend from
the compressors 102 to the roof top of the building to reach
condensers of the condenser stage, wherein heat is released
to the environment. Accordingly, these lengthy networks of
piping must be filled with refrigerant A for the proper
functioning thereof.
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f00291 The stand-alone evaporative condenser loop 10 and
heat reclaim loop 50 extend from adjacent the compressors
102 to the various condensing units thereof, namely the
evaporative condenser 14, the heat reclaim coil 54 and the
air heating unit 56. Therefore, the evaporative condenser
line 110 and the heat reclaim line 112 are substantially
shortened, whereby the amount of refrigerant A in the
refrigeration system 100 is greatly reduced. As the
refrigerant B must not sustain great variations in
temperature as compared to the refrigerant A which must rise
above the outdoor temperature to condense and drop below the
refrigerator temperature to evaporate, the sole purpose of
the refrigerant B is to absorb heat to condense the
refrigerant A. Therefore, refrigerant B may be any of the
following: ethylic acetate, acetic acid, sulfuric acid,
ammoniac, calcium chloride, hydrogen chloride, methylene
chloride, sodium chloride, vinyl chloride, carbon dioxide,
ethanol, ethylene glycol, acetate formiate, potassium
formiate, iso-butane, Pekasol 50, propane, propylene glycol,
toluene, trichloroethylene. In any event, refrigerant B is
chosen amongst safer fluids than refrigerant A. As the
piping of the refrigeration system 100 is greatly reduced,
the compressors 102 are not required to outlet compressed
refrigerant at pressures as high as for longer refrigeration
lines. The compressors can operate at head pressures of
about 120 psi instead of 220 psi, thereby reducing their
operating time and increasing their life-span. Therefore,
substantial savings are achieved in electricity consumption
of the compressors 102, and the life of the compressors 102
is increased.
too3o~ The three-way control valve 104 and the modulating
valves 105 and 107 redirect the flow of refrigerant A
towards heat exchanger 12 or heat exchanger 52 according to
the seasonal heat requirements of the building in which the
refrigeration system 100 is. The stand-alone heat reclaim
loop 50 advantageously recuperates the heat produced by the
compressors 102. The evaporative condenser 14 of the stand-
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alone evaporative condenser loop 10 may either release the
heat outdoors, or recover the heat by, for instance,
spraying a liquid such as water on the coils of the
evaporative condenser 14 to absorb the excess heat. Thus,
in the fall, winter and spring seasons, a greater amount of
refrigerant is circulated in the heat exchanger 52, whereby
the heat absorbed from refrigerant A will serve for heating
the building. It is pointed out that the refrigeration
system 100 may be provided with only one of the evaporative
condenser loop 10 or the heat reclaim loop 50.
(0031 It is within the ambit of the present invention to
cover any obvious modifications of the embodiments described
herein, provided such modifications fall within the scope of
the appended claims.
