A chilling unit and a water circulation temperature control system includes a refrigerant circuit, a pipe through which a heat medium flows, a flow switching valve, 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 connected to each other by pipes. The flow switching valve switches between refrigerant-circulation routes. The controller controls the compressor in accordance with a target outlet temperature, the heat medium temperature detected by the temperature sensor, and a heat medium pressure difference detected by the pressure sensor. When a load on an air handler decreases to a low level and is equal to or less than the compressor's lowest capacity, the controller controls the flow switching valve so that one of the air-side heat exchangers and the heat-medium-side heat exchanger are connected in parallel.

A chilling unit and a water circulation temperature control system includes a refrigerant circuit, a pipe through which a heat medium flows, a flow switching valve, 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 connected to each other by pipes. The flow switching valve switches between refrigerant-circulation routes. The controller controls the compressor in accordance with a target outlet temperature, the heat medium temperature detected by the temperature sensor, and a heat medium pressure difference detected by the pressure sensor. When a load on an air handler decreases to a low level and is equal to or less than the compressor's lowest capacity, the controller controls the flow switching valve so that one of the air-side heat exchangers and the heat-medium-side heat exchanger are connected in parallel.

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 cooling apparatus includes: a first fluid flowpath including the following elements, in downstream flow sequence: a separator vessel; 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 cold sink; 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 separator vessel; 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 cold sink; 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 heat exchanger system has two heat exchangers, a first heat exchanger and a second heat exchanger, mounted within a single enclosure, a first air inlet for receiving air from a first air system, a first air outlet, one or more second air inlets for receiving air from a second air system, one or more second air outlets, a first air path defined as a sealed air path from the first air inlet through the first heat exchanger, to the first air outlet, and a second air path, a third air path and a fourth air path, wherein the first air path transfers heat/energy through the first heat exchanger in a counterflow relation with the third air path, and the second air path transfer heat/energy through the second heat exchanger in a counterflow relation with the fourth air path.

Methods and systems for controlling working fluid flow in a heating, ventilation, air conditioning and refrigeration (HVACR) unit for an HVACR system are disclosed. The unit includes a compressor having a motor and a drive. The unit also includes a condenser fluidly connected to the compressor. A subcooler is located downstream of the condenser. The unit further includes an evaporator fluidly connected to the condenser. Also the unit includes a controller. The unit also includes a bypass assembly connected to the condenser. The bypass assembly includes a bypass flow control device and a bypass fluid line controlled by the bypass flow control device. When a heat recovery demand is detected by the controller, the controller is configured to open the bypass flow control device to allow a first portion of working fluid to bypass the condenser or the subcooler.

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 reheat system of an air conditioning unit includes a bypass line that fluidly couples an outlet of a reheat coil to an input end of a metering device. Further, the reheat system includes a reheat exit line that fluidly couples the outlet of the reheat coil to an input of a condenser. A bypass valve is disposed in the bypass line and a reheat valve is disposed in the reheat exit line. A controller is configured to control the bypass valve and the reheat valve such that a refrigerant from the outlet of the reheat coil is routed to the metering device via the bypass line when an ambient temperature is greater than or equal to a cut-off temperature value that is indicative of a high ambient temperature condition at which the condenser begins operating as an evaporator.