Note: Descriptions are shown in the official language in which they were submitted.
CA 02819308 2013-06-18
REFRIGERATION SYSTEM WITH
PRESSURE-BALANCED HEAT RECLAIM
CROSS-REFERENCE TO RELATED APPLICATIONS
100011 This application claims the benefit of priority to U.S. Provisional
Patent Application
No. 61/663,141, which was filed on June 22, 2012, the complete disclosure of
which is
incorporated by reference herein.
FIELD
[0002] The present disclosure relates generally to the field of refrigeration
systems. The
present disclosure relates more particularly to refrigeration systems having
heat reclaim that uses
heat from the compressed refrigerant to provide heating to one or more heat
loads through a heat
reclaim heat exchanger. The present disclosure relates more particularly still
to a refrigeration
system having a pressure regulator that substantially balances the refrigerant
pressures between a
condenser branch of the system having a condenser, and a heat reclaim branch
of the system
having the heat reclaim heat exchanger, during modes of system operation where
refrigerant is
directed through both branches.
BACKGROUND
[0003] This section is intended to provide a background or context to the
invention recited in
the claims. The description herein may include concepts that could be pursued,
but are not
necessarily ones that have been previously conceived or pursued. Therefore,
unless otherwise
indicated herein, what is described in this section is not prior art to the
description and claims in
this application and is not admitted to be prior art by inclusion in this
section.
100041 It is generally known to provide a refrigeration system for use with
one or more
temperature controlled storage devices such as a refrigerator, freezer,
refrigerated merchandiser,
display case, etc., that may be used in commercial, institutional, and
residential applications for
storing or displaying refrigerated or frozen objects. For example, it is known
to provide a
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refrigeration system having a refrigerant for direct expansion to provide
cooling to a heat
exchanger in the temperature-controlled storage devices such as an evaporator
or chiller. It is
also generally known to use waste heat from a compressed refrigerant as a
source of heat for
nearby heating loads. It would be desirable to provide improved operation and
performance of a
refrigeration system having both a condensing branch with a condenser for
condensing the
compressed refrigerant and a heat reclaim branch having a heat reclaim heat
exchanger for
condensing the compressed refrigerant while using the refrigerant as a heat
source for heating
loads.
SUMMARY
[0005] One embodiment of the disclosure relates to a refrigeration system with
pressure-
balanced heat reclaim and includes at least one compressor configured to
discharge a compressed
refrigerant. A heat reclaim branch has a first end configured to receive at
least a first portion of
the compressed refrigerant and a second end, the heat reclaim branch also has
a first refrigerant
pressure drop. A condensing branch has a first end configured to receive at
least a second
portion of the compressed refrigerant and a second end, the second end of the
condensing branch
is fluidly coupled to the second end of the heat reclaim branch, and the
condensing branch has a
second refrigerant pressure drop. A pressure regulation device is disposed on
one of the heat
reclaim branch and the condensing branch and substantially equalizes the first
refrigerant
pressure drop and the second refrigerant pressure drop.
[0006] Another embodiment of the disclosure relates to refrigeration system
with pressure-
balanced heat reclaim and includes at least one compressor configured to
discharge a compressed
refrigerant. A heat reclaim branch has a first end configured to receive at
least a first portion of
the compressed refrigerant and a second end. A heat reclaim valve and a heat
reclaim heat
exchanger are disposed between the first end and the second end of the heat
reclaim branch, and
the heat reclaim heat exchanger transfers heat from the compressed refrigerant
to one or more
heating loads. A condensing branch has a first end configured to receive at
least a second
portion of the compressed refrigerant and a second end, the second end of the
condensing branch
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is fluidly coupled to the second end of the heat reclaim branch. A condenser
and at least one
condenser inlet valve are disposed between the first end and the second end of
the condensing
branch. A pressure regulation device is disposed between the heat reclaim heat
exchanger and
the second end of the heat reclaim branch, and a controller sends a first
output signal to position
the heat reclaim valve, and a second output signal to position the condenser
inlet valve, and a
third output signal to position the pressure regulation device to
substantially balance a first
refrigerant pressure in the heat reclaim branch downstream of the pressure
regulation device with
a second refrigerant pressure in the condensing branch downstream of the
condenser.
[0007] Yet another embodiment of the disclosure relates to a refrigeration
system for
circulating a refrigerant with pressure-balanced heat reclaim and includes at
least one
temperature-controlled storage device. At least one compressor draws the
refrigerant from the
temperature-controlled storage device and discharges a hot compressed
refrigerant to a discharge
line. A heat reclaim branch has a first end fluidly coupled to the discharge
line and a second end.
A heat reclaim heat exchanger is disposed between the first end and the second
end of the heat
reclaim branch and transfers heat from the hot compressed refrigerant to one
or more heating
loads. A condensing branch has a first end fluidly coupled to the discharge
line and a second end
fluidly coupled to the second end of the heat reclaim branch. A condenser is
disposed between
the first end and the second end of the condensing branch. A pressure
regulation device is
disposed between the heat reclaim heat exchanger and the second end of the
heat reclaim branch
and is operable to substantially balance a refrigerant pressure in the heat
reclaim branch
downstream of the pressure regulation device with a refrigerant pressure in
the condensing
branch downstream of the condenser.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The disclosure will become more fully understood from the following
detailed
description, taken in conjunction with the accompanying figures, wherein like
reference
numerals refer to like elements, in which:
[0009] FIG. 1 is a schematic diagram of a refrigeration system having a
condensing branch
with a condenser for condensing the compressed refrigerant and a heat reclaim
branch having a
heat reclaim heat exchanger for using the compressed refrigerant as a heat
source for heating
loads, according to an exemplary embodiment.
[0010] FIG. 2 is a block diagram of a controller for operating the
refrigeration system of FIG. 1
in a condensing operating mode, a heat reclaim operating mode, and a combined
operating mode,
and for balancing pressure drops associated with the condensing branch and the
heat reclaim
branch, according to an exemplary embodiment.
[0011] FIG. 3 is a flowchart of a process for switching between the condensing
operating
mode, the heat reclaim operating mode, and the combined operating mode,
according to an
exemplary embodiment.
DETAILED DESCRIPTION
[0012] Referring generally to the FIGURES, systems and methods for balancing
pressure in a
heat reclaim refrigeration system are shown. The systems and methods described
herein may be
used to equalize the pressure drops associated with refrigerant flow through a
condensing branch
and a parallel heat reclaim branch of the heat reclaim refrigeration system. A
pressure regulation
device positioned along at least one of the condensing branch and the heat
reclaim branch is used
to effectuate the pressure balance. Advantageously, balancing the pressure
drops associated with
the heat reclaim branch and the condensing branch may facilitate proper
operation of the heat
reclaim refrigeration system by preventing the refrigerant from backing up or
ceasing to flow
through one or more of the heat reclaim branch and the condensing branch.
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[0013] Referring now to FIG. 1, a heat reclaim refrigeration system 10 is
shown, according to
an exemplary embodiment. Refrigeration system 10 may be used to circulate a
refrigerant
through one or more temperature controlled storage devices 20 (e.g.
refrigerated cases, freezers,
etc.) to provide cooling for the temperature-controlled storage devices 20. In
some
embodiments, refrigeration system 10 is a vapor compression refrigeration
system.
100141 Refrigeration system 10 is shown to include expansion devices 22,
temperature-
controlled storage devices 20, and compressors 26. Expansion devices 22 may be
electronic
expansion valves or other similar expansion valves which cause the refrigerant
to expand to a
low pressure, low temperature state. The expanded refrigerant is provided
through temperature-
controlled storage devices 20 (e.g., evaporators of a vapor compression
refrigeration system) for
removing heat from temperature-controlled storage devices 20. Compressors 26
draw the
refrigerant from temperature-controlled storage devices 20 and compress the
refrigerant to a high
temperature and high pressure compressed refrigerant gas. Compressors 26
discharge the hot
compressed gas to a discharge line 28 for circulation through refrigeration
system 10.
[0015] Still referring to FIG. 1, refrigeration system 10 is shown to include
condensing branch
30 and a heat reclaim branch 50. Condensing branch 30 and heat reclaim branch
50 may be
arranged in parallel such that the refrigerant from discharge line 28 can flow
independently
through either condensing branch 30, or heat reclaim branch 50 (e.g., without
flowing through
the other), or through both condensing branch 30 and heat reclaim branch 50 in
parallel.
100161 Condensing branch 30 is shown to include a condenser 32 for cooling
and/or
condensing the compressed refrigerant. In some embodiments, condenser 32 is an
air cooled
condenser. Condenser 32 may be a "split condenser" having one or more sections
that operate
independently (e.g., in parallel) to provide cooling for the compressed
refrigerant. For example,
condenser 32 is shown to include two sections 34 and 36 having a 25% capacity
and a section 38
having a 50% capacity relative to the total capacity of condenser 32. Sections
34-38 may be
selectively utilized by operation of condenser inlet valves 40-42. For
example, condenser inlet
valve 40 may be operated (e.g., opened or closed) to control the flow of the
compressed
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refrigerant through 50% section 38. Similarly, condenser inlet valves 41 and
42 may by operated
to control the flow of the compressed refrigerant through 25% sections 36 and
34 respectively.
Condenser inlet valves 40-42 may be solenoid valves operated by a signal from
a controller (e.g.,
controller 70 described in greater detail with reference to FIG. 2).
[0017] Condensing branch 30 is shown to further include a gas bypass valve 46.
Gas bypass
valve 46 may be a mechanical valve configured to open when the pressure
upstream of valve 46
exceeds a threshold pressure. Gas bypass valve 46 may allow the compressed
refrigerant to
bypass condenser inlet valve 42 and flow through 25% section 34 regardless of
the position of
condenser inlet valve 42. In some embodiments, gas bypass valve is an -open on
rise pressure"
mechanical valve configured to receive a pressure signal from pressure sensor
80. Pressure
sensor 80 may be positioned along refrigerant line 28, downstream of
compressors 26. Gas
bypass valve 46 may be configured to open when the pressure measured by
pressure sensor 80
exceeds a predetermined value. In some embodiments, the predetermined value
may be
representative of a safe operating pressure necessary to provide a maximum
amount of heat to
heat reclaim branch 50. Advantageously, gas bypass value 46 may allow excess
refrigerant gas
to be routed through condenser section 34 (e.g., to provide additional
cooling, to alleviate excess
pressure, etc.) while avoiding excessive cycling of condenser inlet valve 42.
[0018] Condensing branch 30 is shown to further include condenser outlet
valves 47, 48, and
49. Condenser outlet valves 47-49 may be one-way valves (e.g. check valves)
intended to
prevent reverse flow of refrigerant through condenser 32. For example,
condenser outlet valve
47 may prevent refrigerant from flowing backwards from refrigerant line 44
into 50% section 38.
Similarly, condenser outlet valves 48 and 49 may prevent refrigerant from
flowing backwards
from refrigerant line 44 into 25% sections 36 and 34 respectively.
[0019] Still referring to FIG. 1, refrigeration system 10 is shown to include
a heat reclaim
branch 50. Heat reclaim branch 50 may include one or more heat reclaim heat
exchangers for
using the compressed refrigerant as a heat source for heating loads 54. For
example, heat
reclaim branch 50 is shown to include a first heat reclaim heat exchanger 52
and a second heat
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reclaim heat exchanger 152. Heat reclaim heat exchangers 52 and 152 may be
arranged in
parallel such that either of heat reclaim heat exchangers 52, 152 can be used
independently (e.g.,
without using the other). Heat reclaim heat exchangers 52 and 152 may be
selectively utilized
by operating (e.g., opening and closing) heat reclaim valves 56 and 156
respectively. Heat
reclaim valves 56 and 156 may solenoid valves (e.g., operated by a signal from
controller 70) to
selectively direct refrigerant through first heat reclaim heat exchanged 52
and/or second heat
reclaim heat exchanger 152.
100201 Heat reclaim branch 50 is shown to further include a reheat heat
exchange fluid pump
55 for circulating a separate fluid (e.g. glycol, water/glycol mixture, etc.)
from the loads 54
through heat reclaim heat exchangers 52, 152. Valves 57 and 157 may be
arranged in series with
heat reclaim heat exchangers 52 and 152 respectively for controlling the flow
rate of the separate
fluid through heat reclaim heat exchangers 52, 152. Valves 57 and 157 may be
selectively
opened and closed via a control signal from controller 70.
100211 Although only one heat reclaim branch with two heat reclaim heat
exchangers are
shown for clarity and simplicity, additional heat reclaim heat exchangers
and/or heat reclaim
branches may be included and are within the scope of this disclosure.
According to other
alternative embodiments, the refrigeration system may be a cascade
refrigeration system having
a low temperature subsystem and a medium temperature subsystem, where each of
the low and
medium temperature subsystems may each include one or more heat reclaim heat
exchangers
and/or heat reclaim branches. All such variations are intended to be within
the scope of this
disclosure.
100221 Still referring to FIG. 1, refrigeration system 10 is shown to include
a controller 70.
Controller 70 may be programmed to operate refrigeration system 10 in several
modes of
operation. For example, controller 70 may be configured to operate
refrigeration system 10 in a
total heat reclaim mode, a total condensing mode, and/or a combined heat
reclaim/condensing
mode. In some embodiments, the mode of operation with which controller 70
operates depends
upon the demand of the heating and cooling loads, seasonal/geographical
ambient temperature
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conditions, and/or other factors affecting the condensation of the compressed
refrigerant in
condensing branch 30 or heat reclaim branch 50. Controller 70 and the various
modes of
operation used by controller 70 are described in greater detail with reference
to FIGURE. 2.
100231 Refrigeration system 10 is shown to include a plurality of sensors 72,
74, 76, and 78.
Sensors 72-78 may be temperature sensors, pressure sensors, flow rate sensors,
enthalpy sensors,
or any combination thereof. Sensors 72-78 may provide data signals to
controller 70 indicating
the values of one or more variables measured by sensors 72-78. For example,
sensor 72 may
measure a return temperature of a heat transfer fluid from heating loads 54.
The temperature
measured by sensor 72 may indicate a demand level from heating loads 54.
Sensor 74 may
measure the temperature and/or pressure of the refrigerant at the outlet of
heat reclaim heat
exchangers 52 and 152. The temperature and/or pressure measured by sensor 74
may indicate
the extent to which the refrigerant has been condensed in heat reclaim heat
exchangers 52 and
152. Sensor 76 may include one or more sensors configured to measure the
temperature and/or
pressure of the refrigerant at the outlet of condenser sections 34, 36, and/or
38. The temperature
and/or pressure measured by sensor 76 may indicate the extent to which the
refrigerant has been
condensed in condenser 32. In some embodiments, sensor 76 measures a pressure
of the
refrigerant within a fluid conduit 44 through which the refrigerant exits
condensing branch 30.
Sensor 78 may measure a pressure of the refrigerant in a fluid conduit 58
downstream of heat
reclaim branch 50. In some embodiments, sensor 78 measures a fluid pressure
downstream of
pressure regulation device 60.
100241 Pressure regulation device 60 may be a pressure regulator, a pressure
regulation valve, a
pressure control valve, or other device for regulating the pressure upstream
of pressure regulation
device 60 (e.g., measured by sensor 74) or downstream of pressure regulation
device 60 (e.g.,
measured by sensor 78). Pressure regulation device 60 may receive a control
signal from
controller 70. Advantageously, pressure regulation device 60 may be operated
(e.g., by
controller 70) to equalize or substantially equalize the pressure in fluid
conduits 44 and 58. In
other words, controller 70 regulates a position of the pressure regulation
device 60 so that the
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refrigerant pressure drop in the heat reclaim branch 50 is substantially equal
to the refrigerant
pressure drop in the condensing branch 30.
100251 Referring now to FIG. 2, a block diagram of controller 70 is shown,
according to an
exemplary embodiment. Controller 70 is shown to include a communications
interface 88 and a
processing circuit 90. Communications interface 88 may include wired or
wireless interfaces
(e.g., jacks, antennas, transmitters, receivers, transceivers, wire terminals,
Ethernet ports, WiFi
transceivers, etc.) for conducting data communications with local or remote
devices or systems.
Communications interface 88 may be used to communicate with a wireless
networking device
(e.g., a wireless router, wireless-enabled computer, laptop, tablet, cell
tower, etc.) and/or a wired
networking device (e.g., via an Ethernet cable, a SATA cable, USB cable, or
other physical data
connection).
[0026] Communications interface 88 may allow controller 70 to receive data
signals from the
sensory devices of refrigeration system 10 (e.g., sensors 72-78) and provide
control signals to the
control devices of refrigeration system 10 (e.g., valves 40-42, valves 56 and
156, valves 57 and
157, compressors 26, reheat heat exchange heat pump 55, pressure regulation
device 60, etc.) for
controlling the flow of refrigerant and heat transfer within refrigeration
system 10. For example,
controller 70 may provide control signals to heat reclaim valves 56 and 156 to
regulate the
positions thereof and provide the desired heating to heat loads 54 (e.g., via
first heat reclaim heat
exchanger 52 and second heat reclaim heat exchanger 152). Controller 70 may
provide control
signals to heat reclaim valves 57 and 157 to regulate the positions thereof
and provide the desired
flow rate of the reclaim heat exchange fluid through first heat reclaim heat
exchanger 52 and
second heat reclaim heat exchanger 152 respectively. Controller 70 may provide
control signals
to condenser inlet valves 40-42 to regulate the positions thereof and control
condensation of the
refrigerant in condenser 32. Controller 70 may provide a control signal to
pressure regulation
device 60 to substantially balance the refrigerant pressure in downstream
portion 58 of heat
reclaim branch 50 and downstream portion 44 of condenser branch 30.
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[0027] Processing circuit 90 is shown to include a processor 92 and memory 94.
Processor 92
may be implemented as a general purpose processor, an application specific
integrated circuit
(ASIC), one or more field programmable gate arrays (FPGAs), a CPU, a GPU, a
group of
processing components, or other suitable electronic processing components.
[0028] Memory 94 may include one or more devices (e.g., RAM, ROM, Flash
memory, hard
disk storage, etc.) for storing data and/or computer code for completing
and/or facilitating the
various processes, layers, and modules described in the present disclosure.
Memory 94 may
comprise volatile memory or non-volatile memory. Memory 94 may include
database
components, object code components, script components, or any other type of
information
1() structure for supporting the various activities and information
structures described in the present
disclosure. In some implementations, memory 94 is communicably connected to
processor 92
via processing circuit 90 and includes computer code (e.g., data modules
stored in memory 94)
for executing one or more control processes described herein.
[0029] Still refening to FIG. 2, memory 94 is shown to include a condensing
mode control
module 96, a heat reclaim mode control module 98, a combined operating mode
control module
100, a pressure balance module 102, and an ambient temperature module 104.
[0030] Condensing mode control module 96 may be used to operate refrigeration
system 10 in
a total condensing mode of operation. In the total condensing mode of
operation, controller 70
may direct substantially all of the compressed refrigerant to one or more of
sections 34, 36, 38 of
condenser 32 in condensing branch 30 (e.g., by closing heat reclaim valves 56
and 156, and
opening one or more of condenser inlet valves 40-42). The total condensing
mode of operation
may be used when heating loads 54 are not available or not in use, in order to
condense all or
substantially all of the compressed refrigerant in use by the system 10.
[0031] Heat reclaim mode control module 98 may be used to operate
refrigeration system 10 in
a total heat reclaim mode of operation. In the total heat reclaim mode of
operation, controller 70
may direct all of the compressed refrigerant to heat reclaim heat exchangers
52 and 152 in heat
reclaim branch 50 (e.g., by opening heat reclaim valves 56 and/or 156 and
closing condenser
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inlet valves 40-42). Heat reclaim mode control module 98 may open and close
heat reclaim
valves 56 and 156 individually, simultaneously, staggered in a predetermined
sequence based on
the demands of heat loads 54, or in any other order or sequence. In some
implementations, the
total heat reclaim mode of operation may be used when heating loads 54 and
ambient
temperature conditions (e.g. winter months or geographically colder climates)
are sufficient to
condense all or substantially all of the compressed refrigerant.
[0032] Combined operating mode control module 100 may be used to operate
refrigeration
system 10 in a combined (e.g., mixed, hybrid, partial condensing/heat reclaim,
etc.) mode of
operation. In the combined mode of operation, controller 70 may direct a first
portion of the
compressed refrigerant to one or more of heat reclaim heat exchangers 52 and
152 in heat
reclaim branch 50 (e.g., by modulating a position of heat reclaim valve 56
and/or 156).
Combined operating mode control module 100 may direct the remaining portion of
the
compressed refrigerant to one or more of sections 34, 36, 38 of condenser 32
in condensing
branch 30 (e.g., by modulating a position of condenser inlet valves 40-42).
Combined operating
mode control module 100 may use condenser 32 to condense the remaining
compressed
refrigerant in use by refrigeration system 10 which is not condensed in heat
reclaim heat
exchangers 52 and 152. The combined mode of operation may be used when the
heating loads
54 and ambient temperature conditions are sufficient to condense some, but not
all, of the
compressed refrigerant in use by refrigeration system 10.
[0033] During the combined mode of operation, a pressure drop of the
compressed refrigerant
through heat reclaim heat exchanger 52 and/or 152 in heat reclaim branch 50
may not be the
same (or substantially similar to) a pressure drop of the compressed
refrigerant through
condenser 32 in condensing branch 30. In some embodiments, the refrigerant
pressure drop
through condensing branch 30 is greater than the refrigerant pressure drop
through heat reclaim
branch 50. The greater pressure drop through condensing branch 30 may result
in the refrigerant
pressure in fluid conduit 58 being higher than the refrigerant pressure in
fluid conduit 44.
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[0034] Since fluid conduits 58 and 44 are merged upstream of the refrigeration
loads (e.g.
upstream of temperature-controlled storage devices 20 and expansion devices
22, etc.), the
higher pressure in fluid conduit 58 may impede (or in some instances prevent)
the flow of
refrigerant through condensing branch 30. For example, a higher refrigerant
pressure in fluid
conduit 58 may act as a "back pressure" which holds check valves 47-49 in a
closed position. In
some embodiments, when the flow of refrigerant through condenser 32 is impeded
or prevented
in this manner, the refrigerant may condense and accumulate within condenser
32. In other
words, the refrigerant becomes -trapped." Accumulation of the refrigerant
within condenser 32
may deprive refrigeration system 10 of sufficient refrigerant for proper
performance and
operation of temperature-controlled storage devices 20 (or other refrigeration
loads).
100351 According to other embodiments, the refrigerant pressure drop through
heat reclaim
branch 50 may be greater than the refrigerant pressure drop through condensing
branch 30. The
greater pressure drop through heat reclaim branch 50 may result in the
refrigerant pressure in
fluid conduit 44 being higher than the refrigerant pressure in fluid conduit
58. Both
embodiments are intended to be within the scope of this disclosure.
[0036] Still referring to FIG. 2, controller 70 is shown to include a pressure
balance module
102. Pressure balance module 102 may be configured to balance the pressure of
the refrigerant
in fluid conduit 44 (e.g., downstream of condensing branch 30) with the
pressure of the
refrigerant in fluid conduit 58 (e.g., downstream of heat reclaim branch 50).
Advantageously,
pressure balance module 102 may be used to ensure that the pressure drops
through condensing
branch 30 and heat reclaim branch 50 (e.g., reductions in the refrigerant
pressure caused by
refrigerant flow through condensing branch 30 and heat reclaim branch 50) are
substantially
equal during the combined mode of operation.
[0037] Pressure balance module 102 may provide control signal to pressure
regulation device
60. For embodiments in which the pressure drop through heat reclaim branch 50
is less than the
pressure drop through condensing branch 30, pressure regulation device may be
provided
upstream of fluid conduit 58. For embodiments in which the pressure drop
through condensing
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branch 30 is less than the pressure drop through heat reclaim branch 50,
pressure regulation
device may be provided upstream of fluid conduit 44. During the combined mode
of operation,
pressure balance module 102 may modulate the position of pressure regulation
device 60 (e.g.,
by opening and closing a valve of pressure regulation device 60) to ensure
that the refrigerant
pressure in fluid conduit 44 is equal or substantially equal to the
refrigerant pressure in fluid
conduit 58. Advantageously, balancing the pressures in fluid conduits 44 and
58 may prevent a
back pressure against check valves 47-49, thereby facilitating the flow of
refrigerant through
condenser 32.
[0038] Still refe/Ting to FIG. 2, memory 94 is shown to include an ambient
temperature module
104. Ambient temperature module 104 may control the positions of valves 40-42
in response to
outdoor ambient temperature conditions (e.g., at a location in which
refrigeration system 10 is
installed). Ambient temperature module 104 may receive input from an ambient
temperature
sensor (not shown) and modulate the positions of valves 40-42 based on the
ambient
temperature. Ambient temperature module may control the positions of valves 40-
42 to split
condenser 32 (e.g., by directing refrigerant flow through one or more sections
of condense 32) in
response to the outdoor ambient temperature.
[0039] For example, ambient temperature module 104 may be configured to close
valve 40
when the outdoor ambient temperature is less than a first threshold
temperature value. In some
embodiments, the first threshold temperature value is approximately 50 F -55
F. Ambient
temperature module 104 may be configured to close valve 41 when the outdoor
ambient
temperature is less than a second threshold temperature value. In some
embodiments, the second
threshold temperature value is approximately 30 F -35 F. Closing valves 40 and
41 may cut off
refrigerant flow through condenser portions 38 and 36 respectively.
[0040] Referring now to FIG. 3, a flowchart of a process 200 for controlling
refrigeration
system 10 is shown, according to an exemplary embodiment. Process 200 may be
performed by
controller 70 using one or more of the memory modules described above (e.g.,
memory modules
96-102). Process 200 may be used to switch between a total condensing mode, a
total heat
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reclaim mode, and a combined operating mode based the values of several
measured variables
(e.g., measured by sensors 72-78) and/or inputs received from heating loads
54.
[0041] Process 200 is shown to include operating the refrigeration system in a
total condensing
mode (step 202). Step 202 may include closing valves 56 and 156 (or preventing
valves 56 and
156 from opening) to ensure that the refrigerant flows only through condensing
branch 30. Step
202 may further include opening one or more of valves 40-42 to allow the
refrigerant to flow
through condenser 32. The total condensing mode may be the default operating
mode in the
absence of a call for heating from heating loads 54.
100421 Still referring to FIG. 3, process 200 is shown to further include
receiving a call for
heating (step 204). The call for heating may be received from heating loads
54. Heating loads
54 may reflect a need for additional heat (e.g. from suitable temperature
monitoring
instrumentation associated with the heating loads in the facility, such as
ambient space heating,
hot water heating, etc.). Heating loads 54 tnay include a heating device
(e.g., an air handling
unit, a boiler, etc.) configured to provide heating for the facility in which
refrigeration system 10
operates. In some embodiments, heating loads 54 may open a piping circuit for
fluid flow within
the heating device and send a call for heating to controller 70 signaling a
need for heat.
100431 Process 200 is shown to further include operating the refrigeration in
a first stage heat
reclaim mode (step 206). Step 206 may be performed in response to the call for
heating received
from heating loads 54 (e.g., in step 204). In some embodiments, operating the
refrigeration
system in a first state heat reclaim mode includes initiating operation of
reheat heat exchange
fluid pump 55 for circulating the separate fluid from heat loads 54.
Controller 70 may include an
interlock in which pump 55 will not run if return pressure of the fluid to the
suction of the pump
(e.g., immediately upstream of reheat heat exchange fluid pump 55 )is less
than a predetermined
pressure (e.g. about 2 psig or any other suitable pressure) for a
predetermined period of time (e.g.
about 10 minutes or any other suitable time). Step 206 may include opening
valve 57 to allow
the separate fluid to flow through heat exchanger 52.
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CA 02819308 2013-06-18
100441 Controller 70 operates refrigeration system 10 in a first stage heat
reclaim mode by
sending a control signal to open heat reclaim valve 56. Opening heat reclaim
valve 56 may route
the refrigerant through heat reclaim heat exchanger 52. In some embodiments,
the control signal
sent to heat reclaim valve 56 may be interlocked with a signal from pump 55
indicating that
reheat exchange fluid pump 55 is operating. In some embodiments, operating
refrigeration
system 10 in the first stage heat reclaim mode includes closing valve 40,
thereby preventing the
refrigerant from flowing through 50% condenser portion 38.
100451 Still referring to FIG. 3, process 200 is shown to include determining
whether a heat
reclaim is satisfied (step 208). Step 208 may include receiving an input from
heating loads 54.
In some embodiments, controller 70 may determine that the heat reclaim is
satisfied when
heating loads 54 no longer indicate a need for heating. The heat reclaim may
be satisfied when
sufficient heat has been delivered to heating loads 54 to satisfy the heating
demands. If the result
of the determination in step 208 reveals that the heat reclaim is satisfied,
process 200 is shown to
include operating the system in the total condensing mode (e.g., step 202).
100461 Process 200 is shown to include monitoring a temperature T, of the
reheat heat
exchange fluid (step 210). In some embodiments, step 210 may be performed in
response to a
determination (e.g., in step 208) that the heat reclaim is not satisfied. The
reheat heat exchange
fluid is the fluid pumped by reheat heat exchange fluid pump 55 through
heating loads 54. The
temperature T, of the reheat heat exchange fluid may be measured by sensor 72.
Sensor 72 may
be upstream or downstream of heating loads 54. Controller 70 may monitor the
temperature T,
of the reheat heat exchange fluid by receiving an input signal from sensor 72.
[0047] Still referring to FIG. 3, process 200 is shown to include comparing
the temperature Ty
of the reheat heat exchange fluid with a first threshold temperature value T,
(step 212). Step 212
may be performed to determine whether additional heating is required to meet
the heating
demand from heating loads 54. If the result of the determination in step 212
reveals that the
temperature of the reheat heat exchange fluid is not less than the first
threshold temperature
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CA 02819308 2013-06-18
value (e.g., T, ), controller 70 may continue to operate refrigeration
system 10 in the first
state heat reclaim mode (e.g., by returning to step 206). The first threshold
temperature value T,
may be a predetermined temperature value of approximately 95 F or any other
temperature
value, depending on the particular application.
[0048] Process 200 is shown to further include operating the refrigeration
system of a second
stage heat reclaim mode (step 214). In some embodiments, step 214 may be
performed in
response to a determination (e.g., in step 212) that the temperature of the
reheat heat exchange
fluid is less than the first threshold temperature value (e.g., T, <T1). In
some embodiments, step
214 may be performed in response to a determination that the temperature of
the reheat exchange
fluid has been less than the first threshold temperature value for a
predetermined time period
(e.g., of approximately 10 minutes). In other embodiments, other time values
may be used for
the predetermined time period, depending on the particular implementation of
refrigeration
system 10.
[0049] The second stage heat reclaim mode may be initiated by sending a
control signal from
controller 70 to open heat reclaim valve 156, thereby routing the refrigerant
through heat reclaim
heat exchanger 152. Valve 157 may also be opened (e.g., via a control signal
from controller 70)
to allow the separate heat reclaim fluid to flow through heat reclaim heat
exchanger 152.
[0050] In some embodiments, controller 70 includes interlocks associated with
operation of the
second stage heat reclaim mode. The interlocks associated with the second
stage heat reclaim
mode may cause controller 70 to close valves 41 and 42 associated with the 25%
capacity
sections 34 and 36 of condenser 32 when valve 156 is opened. Closing valves 41
and 42 may
prevent flow of refrigerant through condenser 32. In some embodiments, the
second stage heat
reclaim mode is a total heat reclaim mode in which the entirety of the
refrigerant is routed
through heat reclaim branch 50.
[0051] Still referring to FIG. 3, process 200 is shown to include comparing
the temperature of
the reheat heat exchange fluid T, with a second threshold temperature value
T., (step 216). Step
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CA 02819308 2013-06-18
216 may be performed to determine whether heat reclaim branch 50 is capable of
removing
sufficient heat from the compressed refrigerant. If the result of the
determination in step 216
reveals that the temperature of the reheat heat exchange fluid is not greater
than the second
threshold temperature value (e.g., T, 5_ T,), controller 70 may continue to
operate refrigeration
system 10 in the second state heat reclaim mode (e.g., by returning to step
212). The second
threshold temperature value T, may be a predetermined temperature value of
approximately
108 F or any other temperature value, depending on the particular
implementation of
refrigeration system 10.
[0052] If the result of the determination in step 216 reveals that the
temperature of the reheat
heat exchange fluid is greater than the second threshold temperature (e.g., T,
> T2), controller 70
may revert to operating refrigeration system 10 in the first stage heat
reclaim mode (step 206).
Returning to the first stage heat reclaim mode may include closing heat
reclaim valve 156 to stop
refrigerant flow through second stage heat reclaim heat exchanger 152. Valve
157 may also be
closed to prevent the flow of the separate reheat heat exchange fluid through
heat exchanger 152.
Returning to the first stage heat reclaim mode may further include opening
valves 41-42 to allow
the refrigerant to flow through condenser sections 34 and 36. Controller 70
may start and stop
operation of the second stage heat reclaim mode as needed to supplement the
first stage heat
reclaim mode in meeting the heating demand from the heat loads 54.
[0053] When the system is operated in the second stage heat reclaim mode,
refrigeration
system 10 may attempt to remove all heat from the refrigerant using heat
reclaim branch 50.
System 10 may be operated in the second stage heat reclaim mode, for example,
in response to a
determination (e.g., in step 212) that the temperature of the reheat heat
exchange fluid is less
than the first threshold temperature value (e.g., Tx <T,) or when ambient
temperature conditions
cause ambient temperature module 104 to close all of valves 40-42 (e.g., when
the ambient
temperature is less than 30 F-35 F).
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CA 02819308 2013-06-18
[0054] If the heating devices of heat loads 54 cannot remove sufficient heat
from the
refrigeration loop to maintain the refrigerant pressure at the discharge of
compressors 26 (i.e. in
line 28) at a predetermined level (e.g. a pressure corresponding to
approximately 95 F saturated
discharge temperature), bypass valve 46 may be opened to allow the refrigerant
to bypass closed
valve 42 and flow through condenser section 34. Bypass valve 46 may receive a
signal directly
from sensor 80 indicating a temperature and/or pressure of the refrigerant in
line 28.
Advantageously, bypassing the refrigerant through bypass valve 46 may allow
condensing
branch 30 to remove any excess heat that heat reclaim branch 50 cannot
dissipate through the
heat loads 54.
[0055] Bypass valve 46 may be configured to maintain a closed position when
the pressure in
line 28 is below a predetermined value. The predetermined value may be
representative of a safe
operating pressure necessary to provide a maximum amount of heat to heat
reclaim branch 50.
When the pressure of the compressed hot gas refrigerant in line 28 exceeds the
predetermined
value, bypass valve 46 may open to allow the refrigerant to bypass valve 42
and enter condenser
section 34. Advantageously, using bypass valve 46 in this manner may avoid
excessive cycling
of valve 42 as would otherwise be necessary to remove any excess heat which
cannot be
removed via heat reclaim branch 50. Additionally, bypass valve 46 may reduce
frequency with
which controller 70 is required to switch between operating modes by providing
an additional
mechanism (e.g., independent of controller 70) to remove heat from the
refrigerant.
[0056] According to any exemplary embodiment, pressure regulation device 60
operates
during the combined mode of operation (e.g., when refrigerant is flowing
through both
condensing branch 30 and heat reclaim condensing branch 50) to maintain the
pressure in the
reheat discharge line (i.e., fluid conduit 58) at a level that is
substantially equal to the pressure in
the condensing discharge line (i.e., fluid conduit 44). Advantageously,
pressure regulation
device may prevent check valves 47-49 from closing due to back pressure and
flooding one or
more of the condenser portions 34, 36 and/or 38.
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CA 02819308 2013-06-18
100571 According to any exemplary embodiment, the various temperature-
controlled storage
devices of the present disclosure may have different storage temperature
requirements (e.g. "low
temperature," such as approximately -20 F, or -medium temperature," such as
approximately
25 F). Storage devices may have a variety of applications. One example of a
storage device is a
refrigerated display case in a supermarket for use in displaying refrigerated
or frozen food
products. Such temperature-controlled storage devices may have one or more
glass doors that
provide access to a temperature controlled space, or may have an open front
with an air curtain.
All such variations are intended to be within the scope of this disclosure.
100581 The various temperatures of the storage devices and the refrigerants
illustrated or
described in the various embodiments, are shown by way of example only. A wide
variety of
other temperatures and temperature ranges may be used to suit any particular
application and are
intended to be within the scope of this disclosure. Also, the various flow
rates, capacity and
balancing of refrigerants are described by way of example and may be modified
to suit a wide
variety of applications depending on the number of storage devices, the
temperature
requirements of the storage devices, the heating demands from the heat loads,
the pressure drops
through the one or more sections of the condenser and the heat reclaim heat
exchanger(s), etc.
100591 It should also be noted that any references to "upstream,- and
"downstream" in this
description are merely used to identify the various elements as they are
oriented in the
FIGURES, being relative to a specific direction. These terms are not meant to
limit the element
which they describe, as the various elements may be oriented differently in
various applications.
[00601 As utilized herein, the terms "approximately,- -about,"
"substantially," and similar
terms are intended to have a broad meaning in harmony with the common and
accepted usage by
those of ordinary skill in the art to which the subject matter of this
disclosure pertains. It should
be understood by those of skill in the art who review this disclosure that
these terms are intended
to allow a description of certain features described and claimed without
restricting the scope of
these features to the precise numerical ranges provided. Accordingly, these
terms should be
interpreted as indicating that insubstantial or inconsequential modifications
or alterations of the
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CA 02819308 2013-06-18
subject matter described and claimed are considered to be within the scope of
the invention as
recited in the appended claims.
[0061] It should be noted that the term -exemplary" as used herein to describe
various
embodiments is intended to indicate that such embodiments are possible
examples,
representations, and/or illustrations of possible embodiments (and such term
is not intended to
connote that such embodiments are necessarily extraordinary or superlative
examples).
[0062] The terms "coupled,- -connected,- and the like as used herein mean the
joining of two
members directly or indirectly to one another. Such joining may be stationary
(e.g., permanent)
or moveable (e.g., removable or releasable). Such joining may be achieved with
the two
members or the two members and any additional intermediate members being
integrally formed
as a single unitary body with one another or with the two members or the two
members and any
additional intermediate members being attached to one another.
[0063] It should be noted that the orientation of various elements may differ
according to other
exemplary embodiments, and that such variations are intended to be encompassed
by the present
disclosure.
[0064] It is also important to note that the construction and an-angement of
the elements of the
system with pressure-balanced heat reclaim as shown in the exemplary
embodiments are
illustrative only. Although only a few embodiments of the present disclosure
have been
described in detail, those skilled in the art who review this disclosure will
readily appreciate that
many modifications are possible (e.g., variations in sizes, dimensions,
structures, shapes and
proportions of the various elements, values of parameters, mounting
arrangements, use of
materials, colors, orientations, etc.) without materially departing from the
novel teachings and
advantages of the subject matter recited. For example, elements shown as
integrally formed may
be constructed of multiple parts or elements. It should be noted that the
elements and/or
assemblies of the enclosure may be constructed from any of a wide variety of
materials that
provide sufficient strength or durability, in any of a wide variety of colors,
textures, and
combinations. Additionally, in the subject description, the word -exemplary"
is used to mean
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CA 02819308 2013-06-18
serving as an example, instance or illustration. Any embodiment or design
described herein as
"exemplary- is not necessarily to be construed as preferred or advantageous
over other
embodiments or designs. Rather, use of the word exemplary is intended to
present concepts in a
concrete manner. Accordingly, all such modifications are intended to be
included within the
scope of the present inventions. Other substitutions, modifications, changes,
and omissions may
be made in the design, operating conditions, and arrangement of the preferred
and other
exemplary embodiments without departing from the spirit of the appended
claims.
100651 The order or sequence of any process or method steps may be varied or
re-sequenced
according to alternative embodiments. Any means-plus-function clause is
intended to cover the
structures described herein as performing the recited function and not only
structural equivalents
but also equivalent structures. Other substitutions, modifications, changes
and omissions may be
made in the design, operating configuration, and arrangement of the preferred
and other
exemplary embodiments without departing from the spirit of the appended
claims.
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