Thermodynamic system with liquid circulation system heat exchange

Abstract

A process fluid from a liquid circulation system may be directed to an air-to-fluid heat exchanger in heat exchange relationship with an outdoor heat exchanger of a thermodynamic system connected to the liquid circulation system. One or more valves may be used to control flow from the liquid circulation system to the air-to-fluid heat exchanger. The process fluid at the air-to-fluid heat exchanger may defrost the outdoor heat exchanger, be used for free heating or cooling by being directed to a secondary load, or be used for balancing of a cascade system. Reversible fans may be provided at the outdoor heat exchanger and the air-to-fluid heat exchanger to facilitate these operations.

Description

Technical Field

[0001] The present disclosure relates to a heating, ventilation, air conditioning and refrigeration (HVACR) system including a thermodynamic system loop and a liquid circulation system, wherein the liquid circulation system can exchange heat with an outdoor heat exchanger of the thermodynamic system loop. Background Art

[0002] Under some ambient conditions, the thermal system may experience ice accumulation on the outdoor heat exchanger. The ice accumulation can be removed by operating in a defrost mode, where the hot working fluid is directed to the outdoor heat exchanger to melt the ice. This requires operating in a specific mode and may interrupt the heating operation of the thermal system and reduce the heating efficiency. In addition, the cascade thermal system may experience an imbalance in the heat generation of the system, causing one or both of the thermal systems in the cascade arrangement to operate at a lower efficiency operating condition. Summary of the invention

[0003] The present disclosure relates to a heating, ventilation, air conditioning and refrigeration (HVACR) system including a thermodynamic system loop and a liquid circulation system, wherein the liquid circulation system can exchange heat with an outdoor heat exchanger of the thermodynamic system loop.

[0004] By allowing heat exchange between the liquid circulation system and one or more outdoor heat exchangers of the thermal system loop, various functionalities with no or reduced impact on the operation of the thermal system loop can be provided. Functionality can include, for example, defrosting of the one or more outdoor heat exchangers, capturing heating or cooling to achieve simultaneous service of heating and cooling modes, preheating or precooling of the fluid in the liquid circulation system, and / or supporting cascade operation to increase capacity. In some embodiments, the fluid of the liquid circulation system that performs heat exchange at the one or more outdoor heat exchangers can be selectively obtained from or returned to any one of the return line or the supply line, thereby further enhancing control over these capabilities. Selectively obtaining and / or returning fluid from the return line or the supply line can achieve some functionality and / or improve response to various conditions, including but not limited to operating modes, heating and cooling requirements, ambient conditions, combinations and / or relationships thereof, and the like.

[0005] In an embodiment, a method includes directing a portion of a flow of a process fluid from a liquid circulation system to a heat exchanger configured to exchange heat between the process fluid and an outdoor heat exchanger of a working fluid loop of a thermal system.

[0006] In an embodiment, the process fluid rejects heat to the outdoor heat exchanger. In an embodiment, the method further comprises: determining a defrost operation of the heat exchanger, and wherein directing the portion of the flow of the process fluid from the liquid circulation system to the heat exchanger is performed when the defrost operation is determined. In an embodiment, the flow of the process fluid is directed to a cooling load of the liquid circulation system after leaving the heat exchanger.

[0007] In an embodiment, the process fluid absorbs heat from the outdoor heat exchanger. In an embodiment, the flow of the process fluid after leaving the heat exchanger is directed to a heating load of the hydronic system.

[0008] In an embodiment, the process fluid circulates between the thermodynamic system and a second thermodynamic system in a cascade system, and the process fluid rejects heat to the outdoor heat exchanger such that the process fluid is provided to the second thermodynamic system at a target temperature.

[0009] In an embodiment, the thermal system is selected from the group consisting of a heat pump, a chiller and a combined heating and cooling device.

[0010] In an embodiment, the thermodynamic system and the liquid circulation system include a thermodynamic system configured to circulate a working fluid. The thermodynamic system includes a compressor, a flow reverser, a first heat exchanger configured to perform heat exchange between the working fluid and the surrounding environment, an expander, and a second heat exchanger configured to perform heat exchange between the working fluid and a process fluid. The liquid circulation system is configured to circulate a process fluid. The liquid circulation system includes: a supply line configured to transport the process fluid from the second heat exchanger to a load; a return line configured to transport the process fluid from the load to the second heat exchanger; an air-to-fluid heat exchanger configured to perform heat exchange between the process fluid and the surrounding environment at the first heat exchanger; and one or more valves configured to regulate the flow of the process fluid to the air-to-fluid heat exchanger.

[0011] In an embodiment, the thermal system and the liquid circulation system further include: a secondary load supply line, the secondary load supply line is configured to transport the process fluid from the air to fluid heat exchanger to a secondary load; a secondary load return line is configured to transport the process fluid from the secondary load to the air to fluid heat exchanger; one or more valves, the one or more valves are configured to regulate the flow of the process fluid from the air to fluid heat exchanger to the secondary load supply line; and one or more valves, the one or more valves are configured to regulate the flow of the process fluid from the secondary load return line to the air to fluid heat exchanger. In an embodiment, the secondary load is a cooling load. In an embodiment, the secondary load is a heating load.

[0012] In an embodiment, the load is a second thermal system, the second thermal system being in cascade relationship with the first thermal system. In an embodiment, the thermal system and the liquid circulation system further include a controller configured to determine operation in a defrost mode and control at least one of the one or more valves to allow the process fluid to flow to the air-to-fluid heat exchanger.

[0013] In an embodiment, the thermal system and liquid circulation system further comprises a fan configured to direct air flow through the first heat exchanger and the air-to-fluid heat exchanger. In an embodiment, the fan is reversible.

[0014] In an embodiment, the thermodynamic system further comprises a third heat exchanger configured to perform heat exchange between the working fluid and a second process fluid of a second liquid circulation system, the second liquid circulation system being configured to circulate the second process fluid to a second load. In an embodiment, the second liquid circulation system is configured to selectively provide the second process fluid to the air-to-fluid heat exchanger. In an embodiment, the thermodynamic system and the liquid circulation system further comprise at least one second air-to-fluid heat exchanger, wherein the second liquid circulation system is configured to selectively provide the second process fluid to the at least one second air-to-fluid heat exchanger. In an embodiment, one of the load and the second load is a heating load, and the other of the load and the second load is a cooling load. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagrams of a thermal system and a liquid circulation system according to an embodiment are shown.

[0016] Figure 2 Schematic diagrams of a thermal system and a liquid circulation system according to an embodiment are shown.

[0017] Figure 3 Schematic diagrams of a thermal system and a liquid circulation system according to an embodiment are shown.

[0018] Figure 4 Schematic diagrams of a thermal system and a liquid circulation system according to an embodiment are shown.

[0019] Figure 5 A method of operating a thermal system and a hydronic system to defrost the thermal system is shown.

[0020] Figure 6 Methods of operating a thermal system and a hydronic system to support simultaneous heating and cooling operations are shown.

[0021] Figure 7 Methods of operating a thermal system and a hydronic system to support preheating or precooling are shown.

[0022] Figure 8 Methods of operating a thermal system and a hydronic system to support cascade operation are shown.

[0023] Fig. 9 A schematic diagram of a heating and cooling system according to an embodiment is shown. DETAILED DESCRIPTION

[0024] The present disclosure relates to a heating, ventilation, air conditioning and refrigeration (HVACR) system including a thermodynamic system loop and a liquid circulation system, wherein the liquid circulation system can exchange heat with an outdoor heat exchanger of the thermodynamic system.

[0025] As used herein, a "liquid circulation system" refers to any system that circulates any suitable process fluid to transfer heat from one or more heat sources to one or more heat sinks. Process fluids that can be used in a liquid circulation system as discussed herein include, but are not limited to, water, ethylene glycol, blends thereof, and the like.

[0026] Figure 1Schematic diagram of a thermal system and a liquid circulation system according to an embodiment is shown. The thermal system and liquid circulation system 100 includes a thermal system 102 and a liquid circulation system 104. The thermal system 102 includes a compressor 106, a flow reverser 108, a first heat exchanger 110, an expander 112, and one or more second heat exchangers 114. The liquid circulation system 104 includes the first heat exchanger 110, a supply line 116 from the first heat exchanger 110 to a load 118, and a return line 120 from the load 118 to the first heat exchanger 110. The liquid circulation system 104 further includes a controllable valve 122, an air-to-fluid heat exchanger 124, and a bypass valve 126. The liquid circulation system 104 may further include a temperature sensor 128 and a controller 130. The thermal system and liquid circulation system 100 may also include a fan 132. A pump 134 may be included in the liquid circulation system 104.

[0027] The thermal system and liquid circulation system 100 are configured such that the thermal system 102 is operated to add heat to or remove heat from a process fluid circulating within the liquid circulation system 104. In an embodiment, the thermal system 102 may be a heat pump, a chiller, a combined heating and cooling system (e.g., a multi-pipe heating and cooling system), or the like. The process fluid may exchange heat with a load 118 to serve a heating and / or cooling demand at the load 118.

[0028] The thermal system 102 is configured to circulate a working fluid to add heat to or remove heat from a process fluid. Figure 1 In the illustrated embodiment, the thermal system 102 is a reversible heat pump. In other embodiments, the thermal system 102 may alternatively be any other suitable thermal system for heating or cooling a process fluid through the circulation of a working fluid. The thermal system 102 includes a compressor 106. The compressor 106 may be any suitable compressor for compressing a working fluid. In embodiments, a plurality of compressors 106 may be provided as Figure 1106. The compressed working fluid discharged from the compressor 106 is then directed to the flow reverser 108. The flow reverser 108 is a flow control member configured to control the direction of flow through the thermal system 102 by directing the discharge from the compressor 106 to the first heat exchanger 110 or the one or more second heat exchangers 114. In the heating mode, the flow reverser 108 directs the discharge of the compressor 106 to the first heat exchanger 110 and directs the working fluid received from the one or more second heat exchangers 114 to the compressor 106. In the cooling mode, the flow reverser 108 directs the discharge of the compressor 106 to the one or more second heat exchangers 114 and directs the working fluid received from the first heat exchanger to the compressor 106.

[0029] The first heat exchanger 110 is a heat exchanger configured to exchange heat between a working fluid and a process fluid circulating through the liquid circulation system 104. In a heating mode, the first heat exchanger 110 operates as a condenser for the working fluid, wherein the working fluid rejects heat, thereby heating the process fluid in the liquid circulation system 104. In a cooling mode, the first heat exchanger 110 operates as an evaporator, wherein the working fluid absorbs heat, thereby cooling the process fluid.

[0030] The expander 112 is disposed between the first heat exchanger 110 and the one or more second heat exchangers 114. The expander 112 can be any suitable expander capable of expanding the received working fluid, such as, for example, an expansion valve, an expansion plate, an expansion vessel, one or more expansion orifices, or any other known suitable structure for expanding the working fluid. In an embodiment, the expander 112 is an electronic expansion valve.

[0031] The thermal system 102 further includes one or more second heat exchangers 114. (Multiple) second heat exchangers 110 are heat exchangers configured to exchange heat with the surrounding environment or other suitable heat sources / sinks. In an embodiment, one or more second heat exchangers 114 are outdoor heat exchangers configured to exchange heat with air in the surrounding environment of the thermal system 102. In an embodiment, based on the ambient temperature and the operation of the thermal system 102, for example, when the thermal system 102 is operated to provide heating at a temperature below freezing, frost can accumulate on at least one of the one or more second heat exchangers 114. In the heating mode, the one or more second heat exchangers 114 operate as evaporators, wherein the working fluid absorbs heat from the surrounding environment. In the cooling mode, the one or more second heat exchangers 114 operate as condensers for the working fluid, wherein the working fluid discharges heat to the surrounding environment.

[0032] The liquid circulation system 104 is configured to circulate a process fluid from the first heat exchanger 110, where the process fluid absorbs or rejects heat depending on the operation mode of the thermal system 102, and a load 118, where the process fluid exchanges heat to provide heating or cooling to serve the load 118. In some examples, in the liquid circulation system 104, the process fluid circulation can be driven by the operation of a pump 134. In an embodiment, the pump 134 can be provided at different locations in the liquid circulation system 104. In an embodiment, a plurality of pumps 134 can be provided to circulate the process fluid in the liquid circulation system 104. The liquid circulation system 104 includes a process fluid side of the first heat exchanger 110, where the process fluid absorbs heat from or rejects heat to the working fluid of the thermal system 102. The liquid circulation system 104 includes a supply line 116 from the first heat exchanger 110 to the load 118, and the supply line 116 delivers the process fluid to the load 118. In an embodiment, a pump 134 is disposed along the supply line 116. The load 118 may be any suitable heating and / or cooling load to be served by the operation of the thermal and liquid circulation system 100. As non-limiting examples, the load 118 may be a heating and / or cooling load of a conditioned space, a heat exchanger of another thermal system arranged in cascade with the thermal and liquid circulation system 100, or the like. The process fluid is returned from the load 118 via the return line 120.

[0033] A controllable valve 122 is provided to regulate the flow of process fluid from the return line 120 to each of the air-to-fluid heat exchangers 124. The controllable valve 122 may be any suitable valve capable of providing a variable flow or preventing flow into the corresponding air-to-fluid heat exchanger 124. One controllable valve 122 may be provided for each of the air-to-fluid heat exchangers 124.

[0034] The air-to-fluid heat exchanger 124 is one or more heat exchangers disposed near one or more second heat exchangers 114. In an embodiment, the air-to-fluid heat exchanger 124 and the corresponding second heat exchanger 114 can be disposed in a single multifunctional heat exchange structure. In an embodiment, one air-to-fluid heat exchanger 124 is provided for each of the one or more second heat exchangers 114. The air-to-fluid heat exchanger 124 can be in a heat exchange relationship with the one or more second heat exchangers 114 directly by making a portion contact with the corresponding one or more second heat exchangers 114 or indirectly by air at the air-to-fluid heat exchanger 124 and the corresponding second heat exchanger 114 (e.g., air flow driven by the corresponding fan 132). Based on the ambient conditions and / or the temperature at the second heat exchanger 114, the process fluid can absorb or discharge heat at the air-to-fluid heat exchanger 124. In an embodiment, the process fluid may reject heat at the air-to-fluid heat exchanger 124 such that the heat is at least partially absorbed by frost accumulated on the corresponding second heat exchanger 114 , thereby melting the frost and defrosting the second heat exchanger 114 .

[0035] A bypass valve 126 is disposed along the return line 120 . The bypass valve 126 may regulate flow through the return line 120 without passing through the controllable valve 122 , and thus bypass the air-to-fluid heat exchanger 124 .

[0036] The temperature sensor 128 may be disposed in the liquid circulation system 104. The temperature sensor 128 may be positioned to measure a suitable temperature for controlling the liquid circulation system 104, for example, a supply temperature in the supply line 116, a return temperature in the return line 120, a thermodynamic system entry temperature at the inlet of the process fluid side of the first heat exchanger 110, and / or a thermodynamic system exit temperature at the outlet of the process fluid side of the first heat exchanger 110. The thermodynamic system and the liquid circulation system 100 may include a controller 130. In an embodiment, the controller 130 is configured to control the controllable valve 122 and the bypass valve 126. The controller 130 may be configured to control the controllable valve 122 and the bypass valve 126 based on, for example, a call to perform a defrost operation (to achieve a specific target value of at least one of the temperatures measured by the temperature sensor 128), or any other suitable basis for controlling the controllable valve 122 and the bypass valve 126.

[0037] A fan 132 may be disposed at or near each of the one or more second heat exchangers 114 and the corresponding air-to-fluid heat exchanger 124. In an embodiment, the fan 132 may be a controllable fan with a variable speed. In an embodiment, the fan 132 may be reversible so that air may be pulled through or pushed into the second heat exchanger 114 and the corresponding air-to-fluid heat exchanger 124. In an embodiment, the reversibility of the fan 132 may allow either the second heat exchanger 114 or the air-to-fluid heat exchanger 124 to be the first heat exchanger in the corresponding heat exchangers 114, 124 to first receive ambient air driven or drawn by the fan 132.

[0038] Figure 2 A schematic diagram of a thermal system and a liquid circulation system according to an embodiment is shown. The thermal system and liquid circulation system 200 includes a thermal system 202 and a liquid circulation system 204. The thermal system 202 includes a compressor 206, a flow reverser 208, a first heat exchanger 210, an expander 212, and one or more second heat exchangers 214. The liquid circulation system 204 includes the first heat exchanger 210, a supply line 216 from the first heat exchanger 210 to a load 218, and a return line 220 from the load 218 to the first heat exchanger 210. The liquid circulation system 204 further includes a controllable valve 222, an air-to-fluid heat exchanger 224, and a bypass valve 226. The liquid circulation system 204 may further include a temperature sensor 228 and a controller 230. The thermal system and liquid circulation system 200 may also include a fan 232. A pump 234 may be included in the liquid circulation system 204.

[0039] The thermal system and liquid circulation system 200 are configured such that the thermal system 202 is operated to add heat to or remove heat from a process fluid circulating within the liquid circulation system 204. The process fluid may exchange heat with a load 218 to service heating and / or cooling requirements at the load 218.

[0040] The thermal system 202 is a reversible thermal system configured to circulate a working fluid to add heat to or remove heat from a process fluid. The thermal system 202 includes a compressor 206. The compressor 206 may be any suitable compressor for compressing a working fluid. In an embodiment, a plurality of compressors 206 may be provided as Figure 2206. The compressed working fluid discharged from the compressor 206 is then directed to the flow reverser 208. The flow reverser 208 is a flow control member configured to control the direction of flow through the thermal system 202 by directing the discharge from the compressor 206 to the first heat exchanger 220 or the one or more second heat exchangers 214. In the heating mode, the flow reverser 208 directs the discharge of the compressor 206 to the first heat exchanger 210 and directs the working fluid received from the one or more second heat exchangers 214 to the compressor 206. In the cooling mode, the flow reverser 208 directs the discharge of the compressor 206 to the one or more second heat exchangers 214 and directs the working fluid received from the first heat exchanger to the compressor 206.

[0041] The first heat exchanger 210 is a heat exchanger configured to exchange heat between a working fluid and a process fluid circulating through the liquid circulation system 204. In a heating mode, the first heat exchanger 210 operates as a condenser for the working fluid, wherein the working fluid rejects heat, thereby heating the process fluid in the liquid circulation system 204. In a cooling mode, the first heat exchanger 210 operates as an evaporator, wherein the working fluid absorbs heat, thereby cooling the process fluid.

[0042] The expander 212 is disposed between the first heat exchanger 210 and the one or more second heat exchangers 214. The expander 212 can be any suitable expander capable of expanding the received working fluid, such as, for example, an expansion valve, an expansion plate, an expansion vessel, one or more expansion orifices, or any other known suitable structure for expanding the working fluid. In an embodiment, the expander 212 is an electronic expansion valve.

[0043] The thermal system 202 further includes one or more second heat exchangers 214. (Multiple) second heat exchangers 214 are heat exchangers configured to exchange heat with the surrounding environment or other suitable heat sources / heat sinks. In an embodiment, one or more second heat exchangers 214 are outdoor heat exchangers configured to exchange heat with air in the surrounding environment of the thermal system 202. In an embodiment, based on the ambient temperature and the operation of the thermal system 202, for example, when the thermal system is operated to provide heating at a temperature below freezing, frost can accumulate on at least one of the one or more second heat exchangers 214. In the heating mode, the one or more second heat exchangers 214 operate as evaporators, wherein the working fluid absorbs heat from the surrounding environment. In the cooling mode, the one or more second heat exchangers 214 operate as condensers for the working fluid, wherein the working fluid discharges heat to the surrounding environment.

[0044] The liquid circulation system 204 is configured to circulate a process fluid from the first heat exchanger 210, where the process fluid absorbs or rejects heat depending on the operation mode of the thermal system 202, and a load 218, where the process fluid exchanges heat to provide heating or cooling to serve the load 218. In some examples, in the liquid circulation system 204, the process fluid circulation can be driven by the operation of a pump 234. In an embodiment, the pump 234 can be disposed at different locations in the liquid circulation system 204. In an embodiment, a plurality of pumps 234 can be disposed to circulate the process fluid in the liquid circulation system 204. The liquid circulation system 204 includes a process fluid side of the first heat exchanger 210, where the process fluid absorbs heat from or rejects heat to the working fluid of the thermal system 202. The liquid circulation system 204 includes a supply line 216 from the first heat exchanger 210 to the load 218, and the supply line 216 delivers the process fluid to the load 218. In an embodiment, a pump 234 is disposed along the supply line 216. The load 218 may be any suitable heating and / or cooling load to be served by the operation of the thermal and liquid circulation system 200. As non-limiting examples, the load 218 may be a heating and / or cooling load of a conditioned space, a heat exchanger of another thermal system arranged in cascade with the thermal and liquid circulation system 200, or the like. The process fluid is returned from the load 218 via the return line 220.

[0045] A controllable valve 222 is provided to regulate the flow of process fluid from the supply line 216 to each of the air-to-fluid heat exchangers 224. The controllable valve 222 may be any suitable valve capable of providing a variable flow or preventing flow into the corresponding air-to-fluid heat exchanger 224. One controllable valve 222 may be provided for each of the air-to-fluid heat exchangers 224.

[0046] The air-to-fluid heat exchanger 224 is one or more heat exchangers disposed near one or more second heat exchangers 214. In an embodiment, the air-to-fluid heat exchanger 224 and the corresponding second heat exchanger 214 can be disposed in a single multifunctional heat exchange structure. In an embodiment, one air-to-fluid heat exchanger 224 is provided for each of the one or more second heat exchangers 214. The air-to-fluid heat exchanger 224 can be in a heat exchange relationship with the one or more second heat exchangers 214 directly by making a portion contact with the corresponding one or more second heat exchangers 214 or indirectly by air (e.g., air flow driven by a corresponding fan 232) at the air-to-fluid heat exchanger 224 and the corresponding second heat exchanger 214. Based on the ambient conditions and / or the temperature at the second heat exchanger 214, the process fluid can absorb or discharge heat at the air-to-fluid heat exchanger 224. In an embodiment, the process fluid may reject heat at the air-to-fluid heat exchanger 224 such that the heat is at least partially absorbed by frost accumulated on the corresponding second heat exchanger 214 , thereby melting the frost and defrosting the second heat exchanger 214 .

[0047] A bypass valve 226 is disposed along the supply line 216. The bypass valve 226 may regulate flow through the supply line 216 without passing through the controllable valve 222, and thus bypass the air-to-fluid heat exchanger 224.

[0048] A temperature sensor 228 may be provided in the liquid circulation system 204. The temperature sensor 228 may be positioned to measure a suitable temperature for controlling the liquid circulation system 204, for example, a supply temperature in the supply line 216, a return temperature in the return line 220, a thermodynamic system entry temperature at the inlet of the process fluid side of the first heat exchanger 210, and / or a thermodynamic system exit temperature at the outlet of the process fluid side of the first heat exchanger 210. The thermodynamic system and liquid circulation system 200 may include a controller 230. In an embodiment, the controller 230 is configured to control the controllable valve 222 and the bypass valve 226. The controller 230 may be configured to control the controllable valve 222 and the bypass valve 226 based on, for example, a call to perform a defrost operation (to achieve a specific target value of at least one of the temperatures measured by the temperature sensor 228), or any other suitable basis for controlling the controllable valve 222 and the bypass valve 226.

[0049] The fan 232 may be disposed at one or more of the second heat exchangers 214 and the corresponding air-to-fluid heat exchanger 224. In an embodiment, the fan 232 may be a controllable fan with a variable speed. In an embodiment, the fan 232 may be reversible so that air may be pulled through or pushed into the second heat exchanger 214 and the air-to-fluid heat exchanger 224. In an embodiment, the reversibility of the fan 232 may allow either the second heat exchanger 214 or the air-to-fluid heat exchanger 224 to be the first heat exchanger in the corresponding heat exchangers 214, 224 to first receive ambient air driven or drawn by the fan 232.

[0050] Figure 3 A schematic diagram of a thermal system and a liquid circulation system according to an embodiment is shown. The thermal system and liquid circulation system 300 includes a thermal system 302 and a liquid circulation system 304. The thermal system 302 includes a compressor 306, a flow reverser 308, a first heat exchanger 310, an expander 312, and one or more second heat exchangers 314. The liquid circulation system 304 includes the first heat exchanger 310, a supply line 316 from the first heat exchanger 310 to a load 318, and a return line 320 from the load 318 to the first heat exchanger 310. The liquid circulation system 304 further includes a mode control valve 322, a heat exchanger flow control valve 324, an air-to-fluid heat exchanger 326, a supply line bypass valve 328, and a return line bypass valve 330. The liquid circulation system 304 may further include a temperature sensor 332 and a controller 334. The thermal system and liquid circulation system 300 may also include a fan 336. A pump 338 may be included in the liquid circulation system 304 .

[0051] Thermodynamic system and liquid circulation system 300 are configured such that the thermal system 302 is operated to add heat to or remove heat from a process fluid circulating within the liquid circulation system 304. The process fluid may exchange heat with a load 318 to service heating and / or cooling requirements at the load 318.

[0052] Thermodynamic system 302 is a reversible thermodynamic system configured to circulate a working fluid to add heat to or remove heat from a process fluid. Thermodynamic system 302 includes a compressor 306. Compressor 306 may be any suitable compressor for compressing a working fluid. In an embodiment, multiple compressors 306 may be provided as Figure 3306. The compressed working fluid discharged from the compressor 306 is then directed to a flow reverser 308. The flow reverser 308 is a flow control member configured to control the direction of flow through the thermal system 302 by directing the discharge from the compressor 306 to the first heat exchanger 310 or the one or more second heat exchangers 314. In the heating mode, the flow reverser 308 directs the discharge of the compressor 306 to the first heat exchanger 310 and directs the working fluid received from the one or more second heat exchangers 314 to the compressor 306. In the cooling mode, the flow reverser 308 directs the discharge of the compressor 306 to the one or more second heat exchangers 314 and directs the working fluid received from the first heat exchanger 310 to the compressor 306.

[0053] The first heat exchanger 310 is a heat exchanger configured to exchange heat between a working fluid and a process fluid circulating through the liquid circulation system 304. In a heating mode, the first heat exchanger 310 operates as a condenser for the working fluid, wherein the working fluid rejects heat, thereby heating the process fluid in the liquid circulation system 304. In a cooling mode, the first heat exchanger 310 operates as an evaporator, wherein the working fluid absorbs heat, thereby cooling the process fluid.

[0054] The expander 312 is disposed between the first heat exchanger 330 and the one or more second heat exchangers 314. The expander 312 can be any suitable expander capable of expanding the received working fluid, such as, for example, an expansion valve, an expansion plate, an expansion vessel, one or more expansion orifices, or any other known suitable structure for expanding the working fluid. In an embodiment, the expander 312 is an electronic expansion valve.

[0055] The thermal system 302 further includes one or more second heat exchangers 314. (Multiple) second heat exchangers 330 are heat exchangers configured to exchange heat with the surrounding environment or other suitable heat sources / heat sinks. In an embodiment, one or more second heat exchangers 314 are outdoor heat exchangers configured to exchange heat with air in the surrounding environment of the thermal system 302. In an embodiment, based on the ambient temperature and the operation of the thermal system 302, for example, when the thermal system is operated to provide heating at a temperature below freezing, frost can accumulate on at least one of the one or more second heat exchangers 314. In the heating mode, the one or more second heat exchangers 314 operate as evaporators, wherein the working fluid absorbs heat from the surrounding environment. In the cooling mode, the one or more second heat exchangers 314 operate as condensers for the working fluid, wherein the working fluid discharges heat to the surrounding environment.

[0056] The liquid circulation system 304 is configured to circulate the process fluid from the first heat exchanger 310, where the process fluid absorbs or rejects heat according to the operation mode of the thermal system 302, and the load 318, where the process fluid exchanges heat to provide heating or cooling to serve the load 318. In the liquid circulation system 304, the process fluid circulation can be driven by the operation of a pump 338. In an embodiment, the pump 338 can be provided at different locations in the liquid circulation system 304. In an embodiment, a plurality of pumps 338 can be provided to circulate the process fluid in the liquid circulation system 304. The liquid circulation system 304 includes a process fluid side of the first heat exchanger 310, where the process fluid absorbs heat from or rejects heat to the working fluid of the thermal system 302. The liquid circulation system 304 includes a supply line 316 from the first heat exchanger 310 to the load 318, and the supply line 316 delivers the process fluid to the load 318. In an embodiment, a pump 338 is disposed along the supply line 316. The load 318 may be any suitable heating and / or cooling load to be served by the operation of the thermal and liquid circulation system 300. As a non-limiting example, the load 318 may be a heating and / or cooling load of a conditioned space, a heat exchanger of another thermal system arranged in cascade with the thermal and liquid circulation system 300, or the like. The process fluid is returned from the load 318 through the return line 320.

[0057] The liquid circulation system 304 further includes a mode control valve 322. The mode control valve 322 is a three-way valve or assembly including a plurality of valves. The mode control valve 322 is configured to control the supply of process fluid to the air-to-fluid heat exchanger 326 and the return of process fluid from the air-to-fluid heat exchanger 326, so that the supply line 316 or the return line 320 is a line of the liquid circulation system 304 that provides the process fluid to the air-to-fluid heat exchanger 326 and receives the returned process fluid from the air-to-fluid heat exchanger 326.

[0058] The heat exchanger flow control valve 324 is a controllable valve provided for each of the air-to-fluid heat exchangers 326. The heat exchanger flow control valve 324 may be disposed between one of the mode control valves 322 and the corresponding air-to-fluid heat exchanger 326 associated with the heat exchanger flow control valve 324. The heat exchanger flow control valve 324 may be any suitable valve capable of providing a variable flow or preventing flow into the corresponding air-to-fluid heat exchanger 224.

[0059] The air-to-fluid heat exchanger 326 is one or more heat exchangers disposed near one or more second heat exchangers 314. In an embodiment, the air-to-fluid heat exchanger 326 and the corresponding second heat exchanger 314 can be disposed in a single multifunctional heat exchange structure. In an embodiment, one air-to-fluid heat exchanger 326 is provided for each of the one or more second heat exchangers 314. The air-to-fluid heat exchanger 326 can be in heat exchange relationship with the one or more second heat exchangers 314 directly by making a portion contact with the corresponding one or more second heat exchangers 314 or indirectly by air at the air-to-fluid heat exchanger 326 and the corresponding second heat exchanger 314 (e.g., air flow driven by a corresponding fan 336). Based on the ambient conditions and / or the temperature at the second heat exchanger 314, the process fluid can absorb or discharge heat at the air-to-fluid heat exchanger 326. In an embodiment, the process fluid may reject heat at the air-to-fluid heat exchanger 326 such that the heat is at least partially absorbed by frost accumulated on the corresponding second heat exchanger 314 , thereby melting the frost and defrosting the second heat exchanger 314 .

[0060] The supply line 316 includes a supply line bypass valve 328. The supply line bypass valve 328 is a controllable valve configured to regulate flow through the supply line 316. The supply line bypass valve 328 can be positioned between pipes connected to the corresponding mode control valve 322. Flow through the supply line bypass valve 328 is not passed to the mode control valve 322, and is therefore passed from the first heat exchanger 310 to the load 318 without passing through any air-to-fluid heat exchanger 326.

[0061] The return line 320 includes a return line bypass valve 330. The return line bypass valve 330 is a controllable valve configured to regulate flow through the return line 320. The return line bypass valve 330 may be positioned between pipes connected to the corresponding mode control valve 322. Flow through the return line bypass valve 330 is not passed to the mode control valve 322, and is therefore passed from the load 318 to the first heat exchanger 310 without passing through any air-to-fluid heat exchanger 326.

[0062] A temperature sensor 332 may be provided in the liquid circulation system 304. The temperature sensor 332 may be positioned to measure a suitable temperature for controlling the liquid circulation system 304, for example, a supply temperature in the supply line 316, a return temperature in the return line 320, a thermodynamic system entry temperature at the inlet of the process fluid side of the first heat exchanger 310, and / or a thermodynamic system exit temperature at the outlet of the process fluid side of the first heat exchanger 310. The thermodynamic system and the liquid circulation system 300 may include a controller 334. In an embodiment, the controller 334 is configured to control the mode control valve 322, the heat exchanger flow control valve 324, the supply line bypass valve 328, and / or the return line bypass valve 330. The controller 334 can be configured to control the mode control valve 322, the heat exchanger flow control valve 324, the supply line bypass valve 328 and / or the return line bypass valve 330 based on, for example, a call to perform a defrost operation (to achieve a specific target value for at least one of the temperatures measured by the temperature sensor 332), or any other suitable basis for controlling the mode control valve 322, the heat exchanger flow control valve 324, the supply line bypass valve 328 and / or the return line bypass valve 330.

[0063] A fan 336 may be provided at one or more of the second heat exchangers 314 and the corresponding air-to-fluid heat exchanger 326. In an embodiment, the fan 336 may be a controllable fan with a variable speed. In an embodiment, the fan 336 may be reversible so that air may be pulled through or pushed into the second heat exchanger 314 and the air-to-fluid heat exchanger 326. In an embodiment, the reversibility of the fan 336 may allow either the second heat exchanger 314 or the air-to-fluid heat exchanger 326 to be the first heat exchanger in the respective heat exchangers 314, 326 to first receive ambient air driven or drawn by the fan 336.

[0064] Figure 4A schematic diagram of a thermal system and a liquid circulation system according to an embodiment is shown. The thermal system and liquid circulation system 400 includes a thermal system 402 and a liquid circulation system 404. The thermal system 402 includes a compressor 406, a flow reverser 408, a first heat exchanger 410, an expander 412, and one or more second heat exchangers 414. The liquid circulation system 404 includes the first heat exchanger 410, a supply line 416 from the first heat exchanger 410 to a load 418, and a return line 420 from the primary load 418 to the first heat exchanger 410. The liquid circulation system 404 further includes a controllable valve 422, an air-to-fluid heat exchanger 424, and a bypass valve 426. The liquid circulation system 404 additionally includes a secondary load supply line 428, a secondary load 430, a secondary load return line 432, a cooling / defrosting control valve 434, and a heating control valve 436. The liquid circulation system 404 may further include a temperature sensor 438 and a controller 440. The thermal system and liquid circulation system 400 may also include a fan 442. A pump 444 may be included in the liquid circulation system 404.

[0065] The thermal system and liquid circulation system 400 are configured such that the thermal system 402 is operated to add heat to or remove heat from a process fluid circulating within the liquid circulation system 404. The process fluid may exchange heat with a primary load 418 to service heating and / or cooling requirements at the primary load 418.

[0066] Thermodynamic system 402 is a reversible thermodynamic system configured to circulate a working fluid to add heat to or remove heat from a process fluid. Thermodynamic system 402 includes a compressor 406. Compressor 406 may be any suitable compressor for compressing a working fluid. In an embodiment, a plurality of compressors 406 may be provided as compressor 406, such as Figure 4 4. The compressed working fluid discharged from the compressor 406 is then directed to the flow reverser 408. The flow reverser 408 is a flow control member configured to control the direction of flow through the thermal system 402 by directing the discharge from the compressor 406 to the first heat exchanger 410 or the one or more second heat exchangers 414. In the heating mode, the flow reverser 408 directs the discharge of the compressor 406 to the first heat exchanger 410 and directs the working fluid received from the one or more second heat exchangers 414 to the compressor 406. In the cooling mode, the flow reverser 408 directs the discharge of the compressor 406 to the one or more second heat exchangers 414 and directs the working fluid received from the first heat exchanger 410 to the compressor 406.

[0067] The first heat exchanger 410 is a heat exchanger configured to exchange heat between a working fluid and a process fluid circulating through the liquid circulation system 404. In a heating mode, the first heat exchanger 410 operates as a condenser for the working fluid, wherein the working fluid rejects heat, thereby heating the process fluid in the liquid circulation system 404. In a cooling mode, the first heat exchanger 410 operates as an evaporator, wherein the working fluid absorbs heat, thereby cooling the process fluid.

[0068] The expander 412 is disposed between the first heat exchanger 410 and the one or more second heat exchangers 414. The expander 412 can be any suitable expander capable of expanding the received working fluid, such as, for example, an expansion valve, an expansion plate, an expansion vessel, one or more expansion orifices, or any other known suitable structure for expanding the working fluid. In an embodiment, the expander 412 is an electronic expansion valve.

[0069] The thermal system 402 further includes one or more second heat exchangers 414. (Multiple) second heat exchangers 414 are heat exchangers configured to exchange heat with the surrounding environment or other suitable heat sources / heat sinks. In an embodiment, one or more second heat exchangers 414 are outdoor heat exchangers configured to exchange heat with air in the surrounding environment of the thermal system 402. In an embodiment, based on the ambient temperature and the operation of the thermal system 402, for example, when the thermal system is operated to provide heating at a temperature below freezing, frost can accumulate on at least one of the one or more second heat exchangers 414. In the heating mode, the one or more second heat exchangers 414 operate as evaporators, wherein the working fluid absorbs heat from the surrounding environment. In the cooling mode, the one or more second heat exchangers 414 operate as condensers for the working fluid, wherein the working fluid discharges heat to the surrounding environment.

[0070] The liquid circulation system 404 is configured to circulate the process fluid from the first heat exchanger 410, where the process fluid absorbs or discharges heat according to the operating mode of the thermal system 402, and the primary load 418, where the process fluid exchanges heat to provide heating or cooling to serve the primary load 418. The liquid circulation system 404 is further configured to selectively circulate the process fluid to the secondary load 430. The process fluid can be circulated between the secondary load 430 and the air-to-fluid heat exchanger 424, so that the air-to-fluid heat exchanger is a heat source or heat sink that supports the heating or cooling of the secondary load 430, respectively. In the liquid circulation system 404, the process fluid circulation can be driven by the operation of the pump 444. The pump 444 can be included in the supply or return associated with the primary load 418, and can also be included in the supply or return associated with the secondary load 430. In an embodiment, the pump 444 can be provided at different locations in the liquid circulation system 404. In an embodiment, a plurality of pumps 444 may be provided to circulate the process fluid in the liquid circulation system 404. The liquid circulation system 404 includes a process fluid side of a first heat exchanger 410, where the process fluid absorbs heat from or discharges heat to the working fluid of the thermal system 402. The liquid circulation system 416 includes a supply line 416 from the first heat exchanger 410 to a primary load 418, the supply line 416 delivering the process fluid to the primary load 418. In an embodiment, the pump 444 is provided along the supply line 416. The primary load 418 may be any suitable heating and / or cooling load to be served by the operation of the thermal system and the liquid circulation system 400. As a non-limiting example, the load may be a heating and / or cooling load of a conditioned space, a heat exchanger of another thermal system arranged in cascade with the thermal system and the liquid circulation system 400, or the like. The process fluid is returned from the primary load 418 via a return line 420.

[0071] A controllable valve 422 is provided to regulate the flow of process fluid from the return line 420 to each of the air-to-fluid heat exchangers 424. The controllable valve 422 may be any suitable valve capable of providing a variable flow or preventing flow into the corresponding air-to-fluid heat exchanger 424. One controllable valve 422 may be provided for each of the air-to-fluid heat exchangers 424.

[0072] The air-to-fluid heat exchanger 424 is one or more heat exchangers disposed near one or more second heat exchangers 414. In an embodiment, the air-to-fluid heat exchanger 424 and the corresponding second heat exchanger 414 can be disposed in a single multifunctional heat exchange structure. In an embodiment, one air-to-fluid heat exchanger 424 is provided for each of the one or more second heat exchangers 414. The air-to-fluid heat exchanger 424 can be directly in heat exchange relationship with the one or more second heat exchangers 414 by making a portion contact with the corresponding one or more second heat exchangers 414 or indirectly through the air at the air-to-fluid heat exchanger 424 and the corresponding second heat exchanger 414 (e.g., air flow driven by the corresponding fan 442). Based on the ambient conditions and / or the temperature at the second heat exchanger 414, the process fluid can absorb or discharge heat at the air-to-fluid heat exchanger 424. The process fluid heated or cooled by absorbing or discharging heat, respectively, can be circulated to the secondary load 430 to provide heating or cooling in order to serve the secondary load 430.

[0073] A bypass valve 426 is disposed along the return line 420. The bypass valve 426 may regulate flow through the return line 420 without passing through the controllable valve 422, and thus bypass the air to fluid heat exchanger 424.

[0074] Secondary load supply line 428 is a fluid line configured to deliver process fluid from air-to-fluid heat exchanger 424 to secondary load 430. Secondary load supply line 428 may extend from one of load / defrost control valves 434 to secondary load 430.

[0075] The secondary load 430 may be a heating or cooling load that can be served by the process fluid based on a temperature range that can be provided by heat exchange at the air-to-fluid heat exchanger. As non-limiting examples, the secondary load 430 may be a reheating load, a dehumidification load, a sensible heating load, a sensible cooling load, a heating or cooling load for a specific portion of the conditioned space, a pre-heating or pre-cooling load, or the like. In an embodiment, the secondary load 430 is a load of the opposite type to the primary load 418. For example, where the primary load 418 is a heating load, the secondary load 430 may be a cooling load, and vice versa. In an embodiment, the secondary load 430 may be the same heating or cooling type, but have a different temperature requirement than the primary load 418.

[0076] Secondary load return line 432 is a fluid line configured to transport process fluid from secondary load 430 back to air-to-fluid heat exchanger 424. Secondary load return line 432 may extend from secondary load 430 to another of load / defrost control valves 434.

[0077] The load / defrost control valve 434 is a set of valves that may include a two-way valve, a three-way valve, and / or an assembly of multiple valves, and is configured to control the fluid connection of the liquid circulation system 404 to control whether the air-to-fluid heat exchanger 424 is in communication with the primary load 418 and the first heat exchanger 410, or with the secondary load 430. In the load service mode, the load / defrost control valve 434 may be configured to block flow from the return line 420 from the primary load 418 to the air-to-fluid heat exchanger 424, and vice versa, and permit the process fluid to circulate between the air-to-fluid heat exchanger 424 and the secondary load 430 through the secondary load supply line 428 and the secondary load return line 432. In defrost mode, or in any other suitable operating mode in which the secondary load 430 is not being served, the load / defrost control valve can be configured to block process fluid flow into the secondary load supply line 428 and out of the secondary load return line 432, and permit flow from the return line 420 from the primary load 418 to the air-to-fluid heat exchanger 424 and back to the return line 420.

[0078] A heating control valve 436 may be provided to allow at least some of the process fluid to circulate to and from the secondary load 430 to bypass the air-to-fluid heat exchanger 424. The heating control valve 436 may be a controllable three-way valve or an assembly including a plurality of valves configured to regulate flow through one of the secondary load return lines 432 and allow at least some of the flow through the secondary load return line 432 to be diverted to the secondary load supply line 428, for example, via a bypass line 446 or any other suitable fluid connection.

[0079] A temperature sensor 438 may be provided in the liquid circulation system 404. The temperature sensor 438 may be positioned to measure a suitable temperature for controlling the liquid circulation system 404, for example, a primary supply temperature in the supply line 416, a primary return temperature in the return line 420, a thermodynamic system entry temperature at the inlet of the process fluid side of the first heat exchanger 410, a thermodynamic system exit temperature at the outlet of the process fluid side of the first heat exchanger 410, a secondary load supply temperature in the secondary load supply line 428, a secondary load return temperature in the secondary load return line 432, and / or a temperature at the air-to-fluid heat exchanger 424. The thermodynamic system and liquid circulation system 400 may include a controller 440. In an embodiment, the controller 440 is configured to control the controllable valve 422, the bypass valve 426, the load / defrost control valve 434, and / or the heating control valve 436. The controller 440 can be configured to control the controllable valve 422, the bypass valve 426, the load / defrost control valve 434 and / or the heating control valve 436, for example, via a call for heating or cooling at the secondary load, a call to perform a defrost operation (to achieve a specific target value for at least one of the temperatures measured by the temperature sensor 438), or any other suitable basis for controlling the controllable valve 422, the bypass valve 426, the load / defrost control valve 434 and / or the heating control valve 436.

[0080] The fan 442 may be disposed at one or more of the second heat exchangers 414 and the corresponding air-to-fluid heat exchanger 424. In an embodiment, the fan 442 may be a controllable fan with a variable speed. In an embodiment, the fan 442 may be reversible so that air may be pulled through or pushed into the second heat exchanger 414 and the air-to-fluid heat exchanger 424. In an embodiment, the reversibility of the fan 442 may allow either the second heat exchanger 414 or the air-to-fluid heat exchanger 424 to be the first heat exchanger in the corresponding heat exchangers 414, 424 to first receive ambient air driven or drawn by the fan 442.

[0081] Figure 5 A method of operating a thermal system and a liquid circulation system to defrost the thermal system is shown. The method 500 includes operating the thermal system to add heat to or remove heat from a process fluid 502, circulating the process fluid to a load 504, directing at least a portion of the process fluid to an air-to-fluid heat exchanger 506, and exchanging heat 508 between the process fluid at the air-to-fluid heat exchanger and frost accumulated at an outdoor heat exchanger of the thermal system.

[0082] At 502, a thermal system is operated to add heat to or remove heat from a process fluid. The operation of adding or removing heat at 502 may include compressing a working fluid, condensing the working fluid at one heat exchanger, expanding the working fluid, and evaporating the working fluid at another heat exchanger. The process fluid may be heated at the heat exchanger when the working fluid is condensed, or cooled when the working fluid is evaporated at the heat exchanger. During such operation, frost may form on a heat exchanger (e.g., one or more second heat exchangers 114 of the thermal system 102), wherein the working fluid exchanges heat with the surrounding environment, particularly when the thermal system is operated to add heat to the process fluid during a heating operation under cold ambient conditions.

[0083] After the process fluid has been heated or cooled at 502, it is circulated to the load at 504 to provide heating or cooling to the load. The load may be, for example, a heating load or cooling load of a conditioned space, a cascade heat exchanger of another thermal system loop, or the like. The process fluid may then be transferred from the load back to the thermal system to be heated or cooled again at 502.

[0084] During the defrost operation according to method 500, at 506, at least a portion of the process fluid is directed to the air-to-fluid heat exchanger. The defrost operation at 506 can be performed based on a command from a controller. The portion of the process fluid can originate from a supply line from a thermal system to a load or a return line from a load to a thermal system. Directing the process fluid to the air-to-fluid heat exchanger at 506 can be performed using a valve controlled by a controller. The portion of the process fluid can be directed through appropriate valves and piping to be transferred to the air-to-fluid heat exchanger.

[0085] At the air-to-fluid heat exchanger, the diverted working fluid is exchanged with an outdoor heat exchanger of the thermal system (e.g., as described above and in Figures 1 to 4 508. The air-to-fluid heat exchanger is positioned so that it can exchange heat with the outdoor heat exchanger of the thermal system directly or through the air between the air-to-fluid heat exchanger and the outdoor heat exchanger. For example, the air can be drawn or driven over both the air-to-fluid heat exchanger and the outdoor heat exchanger by one or more fans. The diverted working fluid is at a relatively higher temperature than the freezing point of water, and thus heat is discharged to the frost, thereby melting the frost away from the outdoor heat exchanger. The process fluid leaving the air-to-fluid heat exchanger can rejoin the process fluid circulating between the thermal system and the load (for example, returning to the side where the process fluid is obtained at 506).

[0086] Figure 6A method of operating a thermal system and a fluid circulation system to support simultaneous heating and cooling operations is shown. The method 600 includes operating a first thermal system to add heat to or remove heat from a first quantity of process fluid 602, circulating the first quantity of process fluid to a primary load 604, directing a second quantity of process fluid to an air-to-fluid heat exchanger 606, and directing the second quantity of process fluid from the air-to-fluid heat exchanger to a secondary load 608. For example, the method described above and in Figure 4 The method 600 is performed using the thermal system and liquid circulation system 400 shown in FIG.

[0087] At 602, a thermodynamic system is operated to add heat to or remove heat from a first portion of a process fluid. The first portion of the process fluid is a portion that circulates between the thermodynamic system and the primary load. The first portion of the process fluid can be kept separate from a second portion of the process fluid that circulates between an air-to-fluid heat exchanger and a secondary load. For example, a valve in a liquid circulation system can be closed to prevent the flow between a portion of the liquid circulation system that circulates the process fluid from the thermodynamic system to the primary load and a portion of the liquid circulation system that circulates the process fluid from the air-to-fluid heat exchanger to the secondary load. The operation of adding or removing heat at 602 can include compressing a working fluid, condensing the working fluid at a heat exchanger, expanding the working fluid, and evaporating the working fluid at another heat exchanger. The first portion of the process fluid can be heated at a heat exchanger when the working fluid is condensed, or cooled when the working fluid is evaporated at a heat exchanger.

[0088] After the first amount of process fluid has been heated or cooled at 602, it is circulated to the primary load at 604 to provide heating or cooling to the load. The load may be, for example, a heating load or cooling load of a conditioned space or the like. A first portion of the process fluid may then be transferred from the load back to the thermal system to be heated or cooled again at 602.

[0089] The second amount of process fluid is directed to the air-to-fluid heat exchanger 606. The second amount of process fluid is a portion of the process fluid in the liquid circulation system that circulates between the air-to-fluid heat exchanger and the secondary load. The second amount of process fluid can be kept separated from the first amount of process fluid, for example, due to the closure of a valve included in the liquid circulation system. At the air-to-fluid heat exchanger 606, the second amount of process fluid can absorb or discharge heat depending on the temperature and ambient conditions of the second amount of process fluid, the absorption or discharge of heat by the outdoor heat exchanger of the thermal system loop, the operation of one or more fans that guide the air flow through the outdoor heat exchanger and / or the air-to-fluid heat exchanger, or the like. In an embodiment, the fan can be controlled to achieve a specific temperature of the second amount of process fluid when the second amount of process fluid leaves the air-to-fluid heat exchanger.

[0090] At 608, a second amount of process fluid is directed from the air-to-fluid heat exchanger to a secondary load. The secondary load may be a heating or cooling load that can be served by the process fluid based on a temperature range that can be provided by heat exchange at the air-to-fluid heat exchanger. As a non-limiting example, the secondary load may be a reheating load, a dehumidification load, a sensible heat load, a sensible cooling load, a heating or cooling load for a specific portion of the conditioned space, or the like. In an embodiment, the secondary load is a load of the opposite type to the primary load. For example, where the primary load is a heating load, the secondary load may be a cooling load, and vice versa. In an embodiment, the secondary load may be of the same heating or cooling type, but has a different temperature requirement than the primary load. At the secondary load, the second amount of process fluid may absorb or discharge heat based on the relative temperature difference between the second amount of process fluid and the secondary load. The second amount of process fluid may circulate back to the air-to-fluid heat exchanger to absorb or discharge heat at 606 to continue serving the secondary load at 608.

[0091] Figure 7 A method of operating a thermal system and a fluid circulation system to support preheating or precooling is shown. The method 700 includes operating a first thermal system to add heat to or remove heat from a process fluid 702, circulating the process fluid to a load 704, directing at least a portion of the process fluid to an air-to-fluid heat exchanger 706, and exchanging heat 708 between the process fluid at the air-to-fluid heat exchanger and an ambient environment at an outdoor heat exchanger of the first thermal system to preheat or precool the process fluid.

[0092] Method 700 may be performed under certain conditions when heating or cooling of the process fluid at the air-to-fluid heat exchanger can support heating or cooling operations of the thermal system. This determination may be based on one or more of ambient temperature, supply temperature of the process fluid, return temperature of the process fluid, predicted heating or cooling at the air-to-fluid heat exchanger, temperature at an outdoor heat exchanger of the thermal system, a temperature target for the supply, efficiency data for a thermal system loop, and the like.

[0093] At 702, a thermal system is operated to add heat to or remove heat from a process fluid. The operations of adding or removing heat at 702 may include compressing a working fluid, condensing the working fluid at one heat exchanger, expanding the working fluid, and evaporating the working fluid at another heat exchanger. The process fluid may be heated at the heat exchanger when the working fluid is condensed, or cooled when the working fluid is evaporated at the heat exchanger.

[0094] After the process fluid has been heated or cooled at 702, it is circulated to the load at 704 to provide heating or cooling to the load. The load may be, for example, a heating load or cooling load of a conditioned space or the like. A first portion of the process fluid may then be transferred from the load back to the thermal system to be heated or cooled again at 702.

[0095] When preheating or precooling is performed according to method 700, at least a portion of the process fluid is directed to an air-to-fluid heat exchanger at 706. Depending on the piping arrangement and / or whether the process fluid is to be preheated or precooled, the process fluid may originate from a supply line or a return line. Directing a portion of the process fluid to the air-to-fluid heat exchanger at 706 may be performed by operating one or more valves by a controller. In an embodiment, the process fluid originates from a return line. In an embodiment, the amount of process fluid directed to the air-to-fluid heat exchanger at 706 is controlled based on the ability to achieve a temperature that supports a heating or cooling operation, which is performed by a thermal system that adds heat to the process fluid at 702 or removes heat from the process fluid.

[0096] At 708, heat is exchanged between the process fluid at the air-to-fluid heat exchanger and the ambient environment at the outdoor heat exchanger of the first thermal system to preheat or precool the process fluid. In an embodiment, at 708, the process fluid at the air-to-fluid heat exchanger may discharge heat at the air-to-fluid heat exchanger based on ambient conditions, operation of a fan, temperature at the outdoor heat exchanger of the first thermal system, and the like, thereby cooling the process fluid to support the operation of the thermal system to cool the load. In an embodiment, at 708, the process fluid at the air-to-fluid heat exchanger may absorb heat at the air-to-fluid heat exchanger based on ambient conditions, operation of a fan, temperature at the outdoor heat exchanger of the first thermal system, and the like, thereby heating the process fluid to support the operation of the thermal system to heat the load. The preheated or precooled process fluid may join the rest of the process fluid circulating between the thermal system and the load so as to be heated or cooled by the thermal system at 702 and serve the heating or cooling load at 704.

[0097] Figure 8 A method of operating a thermal system and a fluid circulation system to support cascade operation is shown. The method 800 includes operating a first thermal system to add heat to or remove heat from a process fluid 802, circulating the process fluid to a cascade heat exchanger 804 of a second thermal system, directing at least a portion of the process fluid to an air-to-fluid heat exchanger 806, and exchanging heat between the process fluid and an environment at the air-to-fluid heat exchanger 808. In one embodiment, the first thermal system and / or the second thermal system may be a heat pump.

[0098] A first thermodynamic system is operated to add heat to or remove heat from a process fluid 802. The first thermodynamic system may be a thermodynamic system arranged in cascade with a second thermodynamic system, configured to supply heating or cooling to support operation of the second thermodynamic system. The operation of adding or removing heat at 802 may include compressing a working fluid, condensing the working fluid at one heat exchanger, expanding the working fluid, and evaporating the working fluid at another heat exchanger. The process fluid may be heated at the heat exchanger when the working fluid is condensed, or cooled when the working fluid is evaporated at the heat exchanger.

[0099] The process fluid circulates from the first thermal system to the cascade heat exchanger 804 of the second thermal system. At the cascade heat exchanger, the process fluid exchanges heat with the working fluid of the second thermal system. In an embodiment, at 802, the first thermal system heats the process fluid, wherein the process fluid is used as a heat source to support the heating operation of the second thermal system. In an embodiment, at 802, the first thermal system cools the process fluid, wherein the process fluid is used as a heat sink to support the cooling operation of the second thermal system.

[0100] A portion of the process fluid is directed to an air-to-fluid heat exchanger 806. The portion of the process fluid directed to the air-to-fluid heat exchanger can be an amount selected to balance the operation of the first thermodynamic system and the second thermodynamic system, for example to achieve a target supply temperature to the second thermodynamic system and / or a target return temperature to the first thermodynamic system. The amount of the process fluid directed to the air-to-fluid heat exchanger can be based on ambient temperature, the supply temperature of the process fluid, the return temperature of the process fluid, the predicted heating or cooling at the air-to-fluid heat exchanger, the temperature at the outdoor heat exchanger of the first thermodynamic system, the supply and / or return temperature target, the efficiency data of the first and / or second thermodynamic system and the like One or more. The amount can be determined by a controller. At 806, the controller can control the valve of the liquid circulation system to direct the process fluid of the amount to the air-to-fluid heat exchanger. In an embodiment, the controller can control the valve of the liquid circulation system to achieve a target fluid inlet temperature from the first thermodynamic system to the cascade heat exchanger.

[0101] At 808, heat is exchanged between the process fluid and the environment at the air-to-fluid heat exchanger. Based on the temperature of the process fluid and the ambient temperature, the temperature at the outdoor heat exchanger of the first thermal system, and / or the operation of the fan, the process fluid absorbs or rejects heat. The process fluid then joins the process fluid circulating between the first thermal system and the second thermal system, thereby affecting the supply and / or return temperature at the respective thermal systems. The effect on the supply and / or return temperature can be controlled, for example, by controlling the portion of the process fluid that is directed to the air-to-fluid heat exchanger at 806 to allow one or both of the first thermal system and the second thermal system to operate at a more efficient operating setting without creating an imbalance in the heating or cooling of the process fluid between the first thermal system and the second thermal system.

[0102] Fig. 9 A schematic diagram of a heating and cooling system according to an embodiment is shown. The heating and cooling system 900 includes a thermal system 902. The thermal system 902 includes one or more compressors 904, at least one first heat exchanger 906, at least one second heat exchanger 908, and at least one third heat exchanger 910. The thermal system 902 includes one or more expanders 912 and valves 914.

[0103] The heating and cooling system 900 further includes a first process fluid loop 916. The first process fluid loop 916 may be used for heating and includes a first supply line 918, a first load 920, and a first return line 922. One or more pumps 924 may be included in the first process fluid loop 916. The first process fluid loop 916 may further include a fluid line 926 and a valve 928 configured to control the flow of process fluid from the first process fluid loop 916 to one or more air-to-fluid heat exchangers 930.

[0104] The heating and cooling system 900 also includes a second process fluid loop 932, for example, for cooling. The second process fluid loop 932 includes a second supply line 934, a second load 936, and a second return line 938. The second process fluid loop 932 may further include one or more pumps 940. The second process fluid loop 932 may further include a fluid line 942 and a valve 944, which is configured to control the flow of the process fluid from the second process fluid loop 932 to one or more air-to-fluid heat exchangers 930.

[0105] The thermal system 902 can be, for example, a combined heating and cooling system capable of heating, cooling, and simultaneous heating and cooling operations. The thermal system 902 can be, for example, a multi-pipe heating and cooling system, such as a four-pipe heating and cooling system. The thermal system 902 circulates a working fluid (e.g., any suitable refrigerant) to provide heating, cooling, or simultaneous heating and cooling.

[0106] Thermodynamic system 902 includes one or more compressors 904 configured to compress a working fluid. One or more compressors 904 can be any suitable type of compressor or a combination thereof. In the case where one or more compressors 904 include multiple compressors, the compressors can be connected in series, in parallel, or a combination thereof.

[0107] The thermal system 902 includes at least one first heat exchanger 906. Each of the at least one first heat exchanger 906 is configured to exchange heat between a working fluid and a first process fluid of a first process fluid loop 916. Each of the at least one first heat exchanger 906 can receive a first process fluid from a first return line 922, pass the first process fluid through the first heat exchanger 906 to exchange heat between the working fluid and the first process fluid, and direct the first process fluid into a first supply line 918 to serve a first load 920.

[0108] The thermal system 902 further includes at least one second heat exchanger 908. Each of the at least one second heat exchanger 908 is configured to exchange heat between the working fluid and the second process fluid of the second process fluid loop 932. Each of the at least one second heat exchanger 908 can receive the second process fluid from the second return line 938, pass the first process fluid through the second heat exchanger 908 to exchange heat between the working fluid and the second process fluid, and direct the first process fluid into the second supply line 934 to serve the second load 936.

[0109] In addition, the thermal system 902 includes at least one third heat exchanger 910. Each of the at least one third heat exchanger is configured to exchange heat between the working fluid and the surrounding environment of the third heat exchanger 910. The third heat exchanger 910 can be configured so that the working fluid can absorb heat or discharge heat based on the surrounding conditions and the temperature of the working fluid when the working fluid is provided at the third heat exchanger 910.

[0110] The thermal system 902 includes one or more expanders 912 disposed along a fluid circuit through which a working fluid circulates. At least one of the one or more expanders 912 may be included in the flow path of the working fluid from the compressor as the working fluid circulates through the thermal system 902. The expander(s) 912 may include any suitable expander capable of expanding the received working fluid, such as, for example, an expansion valve, an expansion plate, an expansion vessel, one or more expansion orifices, combinations thereof, or any other known suitable structure(s) for expanding a working fluid.

[0111] A plurality of valves 914 are provided on the fluid lines of the thermal system 902. In an embodiment, the valves 914 are configured to control the flow through the corresponding connected fluid lines so that two of the first heat exchanger(s) 906, the second heat exchanger(s) 908, and the third heat exchanger(s) 910 are included in the flow path for the working fluid, and another of the first heat exchanger(s) 906, the second heat exchanger(s) 908, and the third heat exchanger(s) 910 is not included in the flow path for the working fluid. In an embodiment, when the thermal system 902 is in a mode in which both the first load 920 and the second load 936 are served (e.g., a combined heating and cooling mode), the valves 914 may be configured to include the first heat exchanger(s) 906 and the second heat exchanger(s) 908 and not include the third heat exchanger(s) 910. In an embodiment, when the thermal system 902 is in a mode in which the first load 920 is served (e.g., a heating mode), the valve 914 can be configured to include the first heat exchanger(s) 906 and the third heat exchanger(s) 910 and not include the second heat exchanger(s) 908. In an embodiment, when the thermal system 902 is in a mode in which the second load 936 is served (e.g., a cooling mode), the valve 914 can be configured to include the second heat exchanger(s) 908 and the third heat exchanger(s) 910 and not include the first heat exchanger(s) 906.

[0112] The first process fluid loop 916 is configured to circulate a first process fluid to serve a first load 920. In an embodiment, the first load 920 is a heating load, and the first process fluid loop 916 is configured so that the first process fluid absorbs heat at the first heat exchanger(s) 906 and discharges heat at the first load 920 to provide heating at the first load 920. The first process fluid loop 916 includes a first supply line 918 configured to transport the first process fluid from the first heat exchanger(s) 906 to the first load 920. The process fluid exchanges heat at the first load 920 and returns from the first load 920 to the first heat exchanger(s) 906 through a first return line 922. One or more pumps 924 may be included in the first process fluid loop 916, for example on the first supply line 918 or the first return line 922, to drive the circulation of the first process fluid through the first process fluid loop 916.

[0113] The first process fluid loop 916 may include a fluid line 926 configured to direct a portion of the first process fluid to at least some of the one or more air-to-fluid heat exchangers 930. The portion of the flow directed to the (multiple) air-to-fluid heat exchangers 930 may be diverted and controlled by a valve 928 disposed at an appropriate location in the first process fluid loop 916. Fig. 9 In the embodiment shown in , valve 928 and fluid line 926 are configured such that the first process fluid provided to (multiple) air-to-fluid heat exchangers 930 is obtained from first supply line 918 and returned to first supply line 918, however, in alternative embodiments, valve 928 and fluid line 926 may alternatively be configured such that the first process fluid provided to (multiple) air-to-fluid heat exchangers 930 is obtained from first return line 922 and returned to first return line 922.

[0114] One or more air-to-fluid heat exchangers 930 are proximate to one or more third heat exchangers 910 such that the air-to-fluid heat exchangers 930 can exchange heat between one or both of the first process fluid and the second process fluid and the surrounding environment of at least one of the third heat exchangers 910. The heat exchange at the air-to-fluid heat exchanger 930 can be, for example, preheating or precooling one or both of the first process fluid and the second process fluid to defrost the at least one of the third heat exchangers 910, or any other suitable result of such heat exchange provided herein. In an embodiment, a plurality of air-to-fluid heat exchangers 930 are provided, wherein some of the plurality of air-to-fluid heat exchangers 930 are configured to receive the first process fluid and others of the plurality of air-to-fluid heat exchangers 930 are configured to receive the second process fluid. In an embodiment, the air-to-fluid heat exchanger 930 can be configured to receive either the first process fluid or the second process fluid.

[0115] The second process fluid loop 932 is configured to circulate a second process fluid to serve a second load 936. In an embodiment, the second load 936 is a cooling load, and the second process fluid loop 932 is configured so that the second process fluid rejects heat at the second heat exchanger(s) 908 and absorbs heat from the second load 936 to provide heating at the second load 936. The second process fluid loop 932 includes a second supply line 934 configured to deliver the second process fluid from the second heat exchanger(s) 908 to the second load 936. The process fluid exchanges heat at the second load 936 and returns from the second load 936 to the second heat exchanger(s) 908 through a second return line 938. One or more pumps 940 may be included in the second process fluid loop 932, for example on the second supply line 934 or the second return line 938, to drive the circulation of the second process fluid through the second process fluid loop 932.

[0116] The second process fluid loop 932 may include a fluid line 942 configured to direct a portion of the second process fluid to at least some of the one or more air-to-fluid heat exchangers 930. In an embodiment, the at least some of the one or more air-to-fluid heat exchangers 930 connected to the second process fluid loop 932 are separated from the one or more air-to-fluid heat exchangers 930 connected to the first process fluid loop 916. The portion of the flow directed to the (multiple) air-to-fluid heat exchangers 930 may be diverted and controlled by a valve 944 disposed at an appropriate location in the second process fluid loop 932. Fig. 9 In the embodiment shown in , valve 944 and fluid line 942 are configured so that the second process fluid provided to (multiple) air-to-fluid heat exchangers 930 is obtained from second supply line 934 and returned to second supply line 934, however, in alternative embodiments, valve 944 and fluid line 942 may alternatively be configured so that the second process fluid provided to (multiple) air-to-fluid heat exchangers 930 is obtained from second return line 938 and returned to second return line 938. |

[0117] One or more fans 946 may be provided at some or all of the air-to-fluid heat exchangers 930 and / or at the corresponding third heat exchangers 910. In an embodiment, the fan 946 may be a controllable fan with a variable speed. In an embodiment, the fan 946 may be reversible so that air may be pulled through or pushed into the third heat exchanger 910 and the corresponding air-to-fluid heat exchanger 930. In an embodiment, the reversibility of the fan 946 may allow either the third heat exchanger 910 or the air-to-fluid heat exchanger 930 to be the first heat exchanger in the corresponding heat exchangers 910, 930, the first heat exchanger first receiving ambient air driven or drawn by the fan 946.

[0118] aspect:

[0119] It should be understood that any of aspects 1-8 may be combined with any of aspects 9-20.

[0120] Aspect 1. A method comprising: directing a portion of a flow of a process fluid from a liquid circulation system to a heat exchanger configured to exchange heat between the process fluid and an outdoor heat exchanger of a working fluid loop of a thermal system.

[0121] Aspect 2. The method of aspect 1, wherein the process fluid rejects heat to the outdoor heat exchanger.

[0122] Aspect 3. The method according to aspect 2 further comprises: determining a defrost operation of the heat exchanger, and wherein when the defrost operation is determined, directing the portion of the flow of the process fluid from the liquid circulation system to the heat exchanger is performed.

[0123] Aspect 4. The method according to aspect 2 or aspect 3, wherein the flow of the process fluid is directed to a cooling load of the liquid circulation system after leaving the heat exchanger.

[0124] Aspect 5. The method of aspect 1, wherein the process fluid absorbs heat from the outdoor heat exchanger.

[0125] Aspect 6. The method of aspect 5, wherein the flow of the process fluid is directed to a heating load of the liquid circulation system after exiting the heat exchanger.

[0126] Aspect 7. The method according to aspect 1, wherein the process fluid circulates between the thermal system and a second thermal system in the cascade system, and the process fluid discharges heat to the outdoor heat exchanger so that the process fluid is provided to the second thermal system at a target temperature.

[0127] Aspect 8. The method according to any one of aspects 1-7, wherein the thermal system is selected from the group consisting of a heat pump, a chiller, and a combined heating and cooling device.

[0128] Aspect 9. A thermal system and a liquid circulation system, comprising:

[0129] A thermal system configured to circulate a working fluid, the thermal system comprising:

[0130] compressor;

[0131] a first heat exchanger configured to exchange heat between the working fluid and an ambient environment;

[0132] expander; and

[0133] a second heat exchanger configured to exchange heat between the working fluid and a process fluid; and

[0134] A liquid circulation system, the liquid circulation system being configured to circulate the process fluid, the liquid circulation system comprising:

[0135] a supply line configured to deliver the process fluid from the second heat exchanger to a load;

[0136] a return line configured to transport the process fluid from the load to the second heat exchanger;

[0137] an air-to-fluid heat exchanger configured to exchange heat between the process fluid and the ambient environment at the first heat exchanger; and

[0138] One or more valves configured to regulate flow of the process fluid to the air-to-fluid heat exchanger.

[0139] Aspect 10. The thermal system and liquid circulation system according to aspect 9, further comprising:

[0140] a secondary load supply line configured to deliver the process fluid from the air-to-fluid heat exchanger to a secondary load;

[0141] a secondary load return line configured to convey the process fluid from the secondary load to the air-to-fluid heat exchanger;

[0142] one or more valves configured to regulate flow of the process fluid from the air-to-fluid heat exchanger to the secondary load supply line; and

[0143] One or more valves configured to regulate flow of the process fluid from the secondary load return line to the air to fluid heat exchanger.

[0144] Aspect 11. The thermal system and liquid circulation system according to aspect 10, wherein the secondary load is a cooling load.

[0145] Aspect 12. The thermal system and liquid circulation system according to aspect 10, wherein the secondary load is a heating load.

[0146] Aspect 13. The thermal system and liquid circulation system according to any one of aspects 9 to 12, wherein the load is a second thermal system, and the second thermal system is in a cascade relationship with the first thermal system.

[0147] Aspect 14. The thermal system and liquid circulation system according to any one of Aspects 9-13 further includes a controller configured to determine operation in a defrost mode and control at least one of the one or more valves to allow the process fluid to flow to the air-to-fluid heat exchanger.

[0148] Aspect 15. The thermal system and liquid circulation system according to any one of aspects 9-14, further comprising a fan configured to direct air flow through the first heat exchanger and the air-to-fluid heat exchanger.

[0149] Aspect 16. The thermal system and liquid circulation system according to aspect 15, wherein the fan is reversible.

[0150] Aspect 17. A thermal system and a liquid circulation system according to any one of Aspects 9-16, wherein the thermal system further includes a third heat exchanger, the third heat exchanger is configured to exchange heat between the working fluid and a second process fluid of a second liquid circulation system, and the second liquid circulation system is configured to circulate the second process fluid to a second load.

[0151] Aspect 18. The thermal system and liquid circulation system of aspect 17, wherein the second liquid circulation system is configured to selectively provide the second process fluid to the air-to-fluid heat exchanger.

[0152] Aspect 19. The thermal system and liquid circulation system according to aspect 17, further comprising at least one second air-to-fluid heat exchanger, wherein the second liquid circulation system is configured to selectively provide the second process fluid to the at least one second air-to-fluid heat exchanger.

[0153] Aspect 20. The thermal system and liquid circulation system according to any one of aspects 17-19, wherein one of the load and the second load is a heating load, and the other of the load and the second load is a cooling load.

[0154] The examples disclosed in this application are to be considered in all respects as illustrative rather than restrictive. The scope of the invention is indicated by the appended claims rather than by the foregoing description; and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.

Claims

1. A method comprising: A portion of a flow of process fluid is directed from the liquid circulation system to a heat exchanger configured to exchange heat between the process fluid and an outdoor heat exchanger of a working fluid loop of a thermal system.

2. The method according to claim 1, wherein: The process fluid rejects heat to the outdoor heat exchanger.

3. The method according to claim 2, further comprising: A defrost operation for the heat exchanger is determined, and wherein directing the portion of the flow of the process fluid from the liquid circulation system to the heat exchanger is performed when the defrost operation is determined.

4. The method according to claim 2, wherein: The flow of the process fluid after exiting the heat exchanger is directed to a cooling load of the liquid circulation system.

5. The method according to claim 1, wherein: The process fluid absorbs heat from the outdoor heat exchanger.

6. The method according to claim 5, wherein: The flow of the process fluid after exiting the heat exchanger is directed to a heating load of the liquid circulation system.

7. The method according to claim 1, wherein: The process fluid circulates between the thermodynamic system and a second thermodynamic system in the cascade system, and the process fluid rejects heat to the outdoor heat exchanger so that the process fluid is provided to the second thermodynamic system at a target temperature.

8. The method according to claim 1, wherein: The thermal system is selected from the group consisting of a heat pump, a chiller, and a combined heating and cooling device.

9. A thermal system and a liquid circulation system, comprising: A thermal system configured to circulate a working fluid, the thermal system comprising: compressor; a first heat exchanger configured to exchange heat between the working fluid and an ambient environment; expander; and a second heat exchanger configured to exchange heat between the working fluid and a process fluid; and A liquid circulation system, the liquid circulation system being configured to circulate the process fluid, the liquid circulation system comprising: a supply line configured to deliver the process fluid from the second heat exchanger to a load; a return line configured to transport the process fluid from the load to the second heat exchanger; an air-to-fluid heat exchanger configured to exchange heat between the process fluid and the ambient environment at the first heat exchanger; and One or more valves configured to regulate flow of the process fluid to the air-to-fluid heat exchanger.

10. The thermal system and liquid circulation system according to claim 9, further comprising: a secondary load supply line configured to deliver the process fluid from the air-to-fluid heat exchanger to a secondary load; a secondary load return line configured to convey the process fluid from the secondary load to the air-to-fluid heat exchanger; one or more valves configured to regulate flow of the process fluid from the air-to-fluid heat exchanger to the secondary load supply line; and One or more valves configured to regulate flow of the process fluid from the secondary load return line to the air to fluid heat exchanger.

11. The thermal system and liquid circulation system according to claim 10, wherein: The secondary load is a cooling load.

12. The thermal system and liquid circulation system according to claim 10, wherein: The secondary load is a heating load.

13. The thermal system and liquid circulation system according to claim 9, wherein: The load is a second thermal system, and the second thermal system is in a cascade relationship with the first thermal system.

14. The thermal and liquid circulation system of claim 9, further comprising a controller configured to determine operation in a defrost mode and control at least one of the one or more valves to allow the process fluid to flow to the air-to-fluid heat exchanger.

15. The thermal and liquid circulation system of claim 9, further comprising a fan configured to direct air flow through the first heat exchanger and the air-to-fluid heat exchanger.

16. The thermal system and liquid circulation system according to claim 15, wherein: The fan is reversible.

17. The thermal system and liquid circulation system according to claim 9, wherein: The thermal system further includes a third heat exchanger configured to exchange heat between the working fluid and a second process fluid of a second liquid circulation system configured to circulate the second process fluid to a second load.

18. The thermal system and liquid circulation system according to claim 17, wherein: The second liquid circulation system is configured to selectively provide the second process fluid to the air-to-fluid heat exchanger.

19. The thermal system and liquid circulation system of claim 17, further comprising at least one second air-to-fluid heat exchanger, wherein: The second liquid circulation system is configured to selectively provide the second process fluid to the at least one second air-to-fluid heat exchanger.

20. The thermal system and liquid circulation system according to claim 17, wherein: One of the load and the second load is a heating load, and the other of the load and the second load is a cooling load.

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