A refrigeration system includes a receiver, a gas bypass valve, a parallel compressor, and a controller. The gas bypass valve and the parallel compressor are fluidly coupled to an outlet of the receiver in parallel and configured to control a pressure of a gas refrigerant in the receiver. The controller is configured to switch from operating the gas bypass valve to operating the parallel compressor to control the pressure of the gas refrigerant in the receiver in response to a value of a process variable crossing a switchover setpoint. The value of the process variable depends on an amount of the gas refrigerant produced by the refrigeration system. The controller is configured to automatically adjust the switchover setpoint in response to the amount of the gas refrigerant produced by the refrigeration system being insufficient to sustain operation of the parallel compressor.

An apparatus for staged startup of air-cooled low charged packaged ammonia refrigeration system includes motorized valves on condenser coil inlets, a main compressor discharge motorized valve, a bypass pressure regulator valve in the main compressor piping, and check valves on the condenser outlets. The condenser inlet motorized valves provide precise control of gas feed to the condensers, so pressure can build without collapsing oil pressure. The condenser outlet contains check valves to prevent liquid backflow during coil isolation. The compressor discharge line contains a motorized valve for regulating discharge pressure at start-up. The motorized valve in the compressor discharge piping includes a bypass with a pressure regulator for precise regulation at minimum discharge pressure. Once discharge pressure rises above the setpoint, the condenser inlet solenoid coils open one at a time. The discharge pressure regulating motorized valve simultaneously regulates the discharge pressure until the condenser maintains discharge pressure.

An air conditioning unit includes: a first refrigeration system including a first evaporator, a first compressor, a first condenser, a first one-way valve, and a first throttling element connected in sequence in a loop as well as a second one-way valve connected in parallel with the first compressor, and a first fluorine pump connected in parallel with the first one-way valve; and a second refrigeration system including a second evaporator, a second compressor, a second condenser, a third one-way valve, and a second throttling element connected in sequence in a loop as well as a fourth one-way valve connected in parallel with the second compressor, and a second fluorine pump connected in parallel with the third one-way valve, where the first evaporator and the second evaporator are arranged front and rear in sequence along a return air cooling duct.

A heating medium compression apparatus includes: first and second compressors compressing a heating medium; suction side and discharge side pipings connecting the first and second compressors to a heat exchanger; a connection piping connecting a discharge side of the first compressor and a suction side of the second compressor in series; and a control unit controlling a flow rate of the heating medium flowing in the suction side piping, the discharge side piping, and the connection piping. The control unit alternatively connects the first or second compressor to the suction side and discharge side pipings, or connects the first and second compressors in series between the suction side and discharge side pipings and performs control such that the flow rate of the heating medium suctioned into the second compressor connected in series becomes higher than that of the heating medium discharged from the first compressor.

The present disclosure relates to a method for controlling a level of superheat during a pump mode of operation of a refrigeration system, wherein the refrigeration system can operate in either the pump mode or a compressor mode, and has an electronically controlled expansion valve (EEV). A controller obtains a stored, predetermined pump differential pressure range able to be produced by a pump of the system. The controller also obtains a stored, predetermined superheat range, and detects a superheat level. When the detected superheat level is outside of the superheat temperature range, the controller commands adjusting at least one of the EEV and a speed of the pump based on whether the detected superheat level is above or below the superheat range, and whether a current pump differential pressure is above or below the predetermined pump differential pressure range.

An economized refrigeration system includes a main refrigerant circuit having a condenser, an evaporator, an economizer, an expansion device intermediate the condenser and the economizer, and a main compressor fluidly connected by a main refrigerant line. The system also includes an economized refrigerant circuit including an auxiliary compressor system and an auxiliary refrigerant line fluidly connecting the economizer to the auxiliary compressor system and fluidly connecting the main refrigerant line to the auxiliary compressor at a location intermediate the main compressor system and the condenser. The auxiliary compressor system is independently controllable with respect to the main compressor system.

An air conditioner and a method of controlling the same are provided. The air conditioner includes first and second compressors capable of performing multi-stage compression, a condenser for condensing a refrigerant compressed in the first and second compressors, a refrigerant separation device for separating the refrigerant to be injected to the first or second compressor of the refrigerant condensed in the condenser, injection tubes extending from the refrigerant separation device to the first and second compressors to guide injection of the refrigerant, a main expansion device disposed at an outlet-side of the refrigerant separation device to decompress the refrigerant, an evaporator for evaporating the refrigerant decompressed in the main expansion device, a valve device disposed at an outlet-side of the first compressor to guide the refrigerant compressed in the first compressor to the condenser or the second compressor, and a bypass tube extending from the valve device to an suction-side of the second compressor.

For more efficient operation of an air cooled chiller, a refrigerant pump and bypass valve connected in parallel feed refrigerant from the condenser to a receiver. The pump is activated in response to pressure in the condenser; the bypass is used otherwise. Further efficiency is provided by controlling the condenser fan based on power consumption by the air cooled chiller and/or resetting a set point of the evaporator to meet load conditions. An expansion valve for the evaporator is controlled based on chilled water temperature, such as Delta T, or information from an air handling unit. Feedback of valve setting or position, air temperature, valve size, and/or importance of an air handling unit may be used to control the flow of chilled water. In addition to or an alternative to control of the chilled water flow, the refrigerant temperature may be controlled based on information from the air handling unit.

A refrigeration cycle device includes a refrigerant circuit switching device. The refrigerant circuit switching device is configured to switch among at least a first circuit and a second circuit. The first circuit conducts refrigerant, which is outputted from a heat releasing device, to a liquid storage and conducts the refrigerant, which is outputted from the liquid storage, to a first depressurizing device and conducts the refrigerant, which is depressurized by the first depressurizing device, to an external heat exchanger. The second circuit conducts the refrigerant, which is outputted from the external heat exchanger, to the liquid storage and conducts the refrigerant, which is outputted from the liquid storage, to a second depressurizing device and conducts the refrigerant, which is depressurized by the second depressurizing device, to an evaporating device.

A heat-pump system may include a compressor, an outdoor heating exchanger, an indoor heat exchanger, an expansion device, and a supplemental heater. The outdoor heat exchanger may be in fluid communication with the compressor. The indoor heat exchanger may be in fluid communication with the compressor. The expansion device may be in fluid communication with the indoor and outdoor heat exchangers. The supplemental heater may include a burner and a working-fluid conduit. The burner may be configured to burn a fuel and heat the working-fluid conduit. When the heat-pump system is operating in a heating mode, the indoor heat exchanger may receive working fluid from the working-fluid conduit such that the working fluid flows from an outlet of the working-fluid conduit to an inlet of the indoor heat exchanger.