In some embodiments, an air-cooled ammonia refrigeration system comprises: a plurality of air-cooled condensers, each having a heat exchanger and at least one axial fan and having a first operating state capable of condensing vaporous ammonia to form liquid ammonia; an evaporator coupled to the air-cooled condenser; a subcooler positioned between the air-cooled condenser and the evaporator; a compressor coupled to the evaporator; an oil cooler coupled to the compressor; and a plurality of valves coupled to the plurality of air-cooled condensers and having a first configuration corresponding to the first operating state of the plurality of air-cooled condensers, and a second configuration corresponding to a second operating state of one or more of the plurality of air-cooled condensers such that the one or more of the plurality of air-cooled condensers functions as an evaporator capable of evaporating liquid ammonia to form vaporous ammonia.

A chilling unit and a temperature control system using water circulation includes a refrigerant circuit, a pipe through which a heat medium flows, a flow switching device, a temperature sensor, a pressure sensor, and a controller. The refrigerant circuit includes a compressor, a pair of air-side heat exchangers, an expansion valve, and a heat-medium-side heat exchanger that are connected to each other by pipes, thereby enabling refrigerant to circulate in the refrigerant circuit. The flow switching device switches between refrigerant-circulation routes. The controller controls the compressor in accordance with a target outlet temperature, the temperature of the heat medium detected by the temperature sensor, and a pressure difference in the heat medium detected by the pressure sensor. When a load on a loading device decreases to a low level and the load is equal to or less than the lowest capacity of the compressor, the controller performs control to avoid starts and stops while keeping the compressor operating at the lowest capacity and controls the flow switching device so that one of the pair of air-side heat exchangers and the heat-medium-side heat exchanger are connected in parallel.

A chilling unit and a temperature control system using water circulation includes a refrigerant circuit, a pipe through which a heat medium flows, a flow switching device, a temperature sensor, a pressure sensor, and a controller. The refrigerant circuit includes a compressor, a pair of air-side heat exchangers, an expansion valve, and a heat-medium-side heat exchanger that are connected to each other by pipes, thereby enabling refrigerant to circulate in the refrigerant circuit. The flow switching device switches between refrigerant-circulation routes. The controller controls the compressor in accordance with a target outlet temperature, the temperature of the heat medium detected by the temperature sensor, and a pressure difference in the heat medium detected by the pressure sensor. When a load on a loading device decreases to a low level and the load is equal to or less than the lowest capacity of the compressor, the controller performs control to avoid starts and stops while keeping the compressor operating at the lowest capacity and controls the flow switching device so that one of the pair of air-side heat exchangers and the heat-medium-side heat exchanger are connected in parallel.

An air-conditioning apparatus reduces occurrence of refrigerant accumulation on a downstream side of an evaporator to favorably circulate refrigerant. The air-conditioning apparatus includes: a main circuit in which a compressor, a refrigerant-flow switching device, a load-side heat exchanger, a load-side expansion device and three heat-source-side heat exchangers are connected by pipes to circulate refrigerant; and a heat-exchanger flow-passage switching device which performs switching to apply a first series refrigerant passage in the case where the three heat-source-side heat exchangers are used as condensers, and switching to apply a parallel refrigerant passage in the case where the three heat-source-side heat exchangers are used as evaporators. In the first series refrigerant passage, on an upstream side, the first and second heat-source-side heat exchangers are connected parallel to each other, and on a downstream side, the third heat-source-side heat exchanger is located. In the parallel refrigerant passage, first to third heat-source-side heat exchanger are connected parallel to each other.

A heating, ventilation, air conditioning, and/or refrigeration (HVAC&R) system includes a process fluid loop configured to receive a process fluid, an internal fluid cooling loop configured to receive a cooling fluid, an air cooled heat exchanger configured to cool the cooling fluid, a vapor compression loop configured to receive a working fluid, and a condenser configured to place the cooling fluid and the working fluid in a first heat exchange relationship. The HVAC&R system also includes a heat exchanger configured to place the cooling fluid and the process fluid in a second heat exchange relationship. The heat exchanger and the condenser are disposed in series relative to a flow of the cooling fluid through the internal fluid cooling loop. The HVAC&R system also includes a pump configured to bias the cooling fluid through the internal fluid cooling loop.

A heating, ventilation, air conditioning, and/or refrigeration (HVAC&R) system includes a first modular central utility plant (mCUP) including a first chiller and a first free cooling heat exchanger, and a second mCUP including a second chiller and a second free cooling heat exchanger. The HVAC&R system also includes at least one dry cooler assembly having an air cooled heat exchanger with one or more fans, wherein the at least one dry cooler assembly is shared between the first mCUP and the second mCUP

A cooling apparatus includes: a first fluid flowpath including the following elements, in downstream flow sequence: a subcooler having a first side in fluid communication with the first fluid flowpath and a second side configured to be disposed in thermal communication with a source of cooling fluid; a flow control valve; a primary evaporator assembly including at least one primary evaporator configured to be disposed in thermal communication with a primary heat load; and a pressure regulator operable to maintain a refrigerant saturation pressure within the primary evaporator at a predetermined set point.

A cooling apparatus includes: a first fluid flowpath including the following elements, in downstream flow sequence: a subcooler having a first side in fluid communication with the first fluid flowpath and a second side configured to be disposed in thermal communication with a source of cooling fluid; a flow control valve; a primary evaporator assembly including at least one primary evaporator configured to be disposed in thermal communication with a primary heat load; and a pressure regulator operable to maintain a refrigerant saturation pressure within the primary evaporator at a predetermined set point.

A CO.sub.2 refrigeration system includes a CO.sub.2 refrigeration subsystem that provides cooling for a refrigeration load using carbon dioxide (CO.sub.2) as a refrigerant. The CO.sub.2 refrigeration system further includes a direct CO.sub.2 heat exchange subsystem that uses the CO.sub.2 refrigerant from the CO.sub.2 refrigeration subsystem to provide heating or cooling for a building zone. The direct CO.sub.2 heat exchange subsystem includes a heat exchanger that exchanges heat directly between the CO.sub.2 refrigerant and an airflow provided to the building zone.

A CO.sub.2 refrigeration system includes a CO.sub.2 refrigeration subsystem that provides cooling for a refrigeration load using carbon dioxide (CO.sub.2) as a refrigerant. The CO.sub.2 refrigeration system further includes a direct CO.sub.2 heat exchange subsystem that uses the CO.sub.2 refrigerant from the CO.sub.2 refrigeration subsystem to provide heating or cooling for a building zone. The direct CO.sub.2 heat exchange subsystem includes a heat exchanger that exchanges heat directly between the CO.sub.2 refrigerant and an airflow provided to the building zone.