CA2819308A1 - Refrigeration system with pressure-balanced heat reclaim - Google Patents

Abstract

A refrigeration system with pressure-balanced heat reclaim 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.

Description

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 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 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.

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.

[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 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 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 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 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.

[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 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.

[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 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 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.

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 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 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).

[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.

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 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 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.

Claims (20)

1. A refrigeration system for circulating a refrigerant with pressure-balanced heat reclaim, comprising:
at least one temperature-controlled storage device;
at least one compressor configured to draw the refrigerant from the temperature-controlled storage device and to discharge a hot compressed refrigerant to a discharge line;
a heat reclaim branch having a first end fluidly coupled to the discharge line and a second end;
a heat reclaim heat exchanger disposed between the first end and the second end of the heat reclaim branch and configured to transfer heat from the hot compressed refrigerant to one or more heating loads;
a condensing branch having a first end fluidly coupled to the discharge line and a second end, the second end of the condensing branch being fluidly coupled to the second end of the heat reclaim branch;
a condenser disposed between the first end and the second end of the condensing branch;
a pressure regulation device disposed between the heat reclaim heat exchanger and the second end of the heat reclaim branch; and wherein the pressure regulation device 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.

2. The system of Claim 1, wherein the condenser is an air-cooled condenser and has a plurality of separate sections for flow of the hot compressed refrigerant through the condenser.

3. The system of Claim 2, further comprising a heat reclaim valve disposed between the first end of the heat reclaim portion and the heat reclaim heat exchanger, the heat reclaim valve operable to divert a first portion of the hot compressed refrigerant to the heat reclaim heat exchanger and away from the condenser.

4. The system of Claim 3, further comprising a check valve disposed on an outlet of each of the sections of the condenser.

5. The system of Claim 4, wherein the pressure regulation device is operable to avoid a backpressure condition downstream of the heat exchanger, where the backpressure condition maintains the check valves in a closed position and prevents flow of the refrigerant through the circuits of the condenser.

6. The device of Claim 5, further comprising a condenser inlet valve disposed on an inlet to each section of the condenser.

7. The device of Claim 6, further comprising a controller operable to regulate a position of the heat reclaim valve, the condenser inlet valves, and the pressure regulation device.

8. The device of Claim 6, further comprising a bypass valve arranged in parallel with a condenser inlet valve, the bypass valve configured to allow the hot compressed refrigerant to bypass the condenser inlet valve and enter the condenser.

9. The device of Claim 8, wherein the bypass valve is configured to allow the hot compressed refrigerant to bypass the condenser inlet valve in response to a pressure of the hot compressed refrigerant in the discharge line exceeding a threshold pressure.

10. A refrigeration system with pressure-balanced heat reclaim, comprising:

at least one compressor configured to discharge a compressed refrigerant;
a heat reclaim branch having 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 disposed between the first end and the second end of the heat reclaim branch, the heat reclaim heat exchanger configured to transfer heat from the compressed refrigerant to one or more heating loads;
a condensing branch having 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 being fluidly coupled to the second end of the heat reclaim branch;
a condenser and at least one condenser inlet valve disposed between the first end and the second end of the condensing branch;
a pressure regulation device disposed between the heat reclaim heat exchanger and the second end of the heat reclaim branch; and a controller configured to send 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.

11. The device of Claim 10, wherein the heat reclaim branch comprises a first refrigerant pressure drop and the condensing branch comprises a second refrigerant pressure drop, the second refrigerant pressure drop being different from the first refrigerant pressure drop.

12. The device of Claim 11, wherein the controller regulates a position of the pressure regulation device so that the first refrigerant pressure drop is substantially equal to the second refrigerant pressure drop.

13. A refrigeration system with pressure-balanced heat reclaim, comprising:

at least one compressor configured to discharge a compressed refrigerant;
a heat reclaim branch having a first end configured to receive at least a first portion of the compressed refrigerant and a second end, the heat reclaim branch having a first refrigerant pressure drop;
a condensing branch having 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 being fluidly coupled to the second end of the heat reclaim branch, the condensing branch having a second refrigerant pressure drop; and a pressure regulation device disposed on one of the heat reclaim branch and the condensing branch and configured to substantially equalize the first refrigerant pressure drop and the second refrigerant pressure drop.

14. The system of Claim 13, further comprising a heat reclaim valve and a heat reclaim heat exchanger disposed between the first end and the second end of the heat reclaim branch, the heat reclaim heat exchanger configured to transfer heat from the compressed refrigerant to one or more heating loads.

15. The system of Claim 14, further comprising a condenser and at least one condenser inlet valve disposed between the first end and the second end of the condensing branch.

16. The device of Claim 15, further comprising a bypass valve arranged in parallel with a condenser inlet valve, the bypass valve configured to allow the compressed refrigerant discharged by the at least one compressor to bypass the condenser inlet valve and enter the condenser.

17. The device of Claim 16, wherein the bypass valve is configured to allow the compressed refrigerant to bypass the condenser inlet valve in response to a pressure of the compressed refrigerant discharged by the at least one compressor exceeding a threshold pressure.

18. The system of Claim 16 further comprising a controller configured to send 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.

19. The system of Claim 18, further comprising at least one check valve disposed on an outlet of the condenser.

20. The system of Claim 19, wherein the pressure regulation device is operable to avoid a backpressure condition downstream of the heat reclaim heat exchanger, where the backpressure condition maintains the check valve in a closed position and prevents flow of the refrigerant through the condenser.