Upon detection of a leakage of refrigerant, a refrigerant recovery operation is performed for operating a compressor in a state where an outdoor expansion valve is closed. The refrigerant suctioned from an indoor unit passes through an outdoor heat exchanger so as to be liquefied and accumulated in an outdoor unit. When a low-pressure detection value by a pressure sensor decreases below a reference value, a termination condition for the refrigerant recovery operation is satisfied, and the compressor is stopped. Furthermore, when an abnormality in the refrigerant recovery operation is detected based on a behavior of the low-pressure detection value obtained until the termination condition is satisfied, the compressor is stopped to thereby end the refrigerant recovery operation. Also, guidance information for notification about an abnormality is output to a user.

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 air-conditioning apparatus is able to ensure an appropriate flow rate of refrigerant and an appropriate amount of oil returned to a compressor that match operation conditions regardless of an operating state of a refrigerant circuit and a change in an operation condition. The air-conditioning apparatus includes: a first detector configured to detect a refrigerant temperature within an accumulator; a storage unit configured to store information regarding a two-layer separation temperature of refrigerant and refrigerating machine oil; a determiner configured to compare the refrigerant temperature with the two-layer separation temperature and determine a two-layer separation state of the refrigerant and the refrigerating machine oil; a second detector configured to detect a state of the refrigerant sucked by the compressor; and a control unit configured to adjust an opening degree of a flow control valve on the basis of the two-layer separation state and a state of the sucked refrigerant.

A refrigeration cycle apparatus includes a compressor, a condenser, a first subcooling device that subcools a refrigerant by exchanging heat with the air, a second subcooling device that performs a heat exchange between refrigerant streams that have been branched by a branch pipe, thereby subcooling one of the refrigerant streams, a flow control device that adjusts a flow rate of the second stream of the refrigerant and passes this refrigerant through the second subcooling device, a bypass path that allows the refrigerant passing through the flow control device and the second subcooling device to flow therethrough, an expansion valve, an evaporator, and a controller configured to control an amount of heat exchanged in the first subcooling device and an amount of heat exchanged in the second subcooling device based on a temperature of the air.

A refrigeration system includes a subcooler configured to provide subcooling for a liquid refrigerant flowing through a first side of the subcooler by transferring heat from the liquid refrigerant to a gas refrigerant flowing through a second side of the subcooler. An expansion valve is located at an inlet of the second side of the subcooler and configured to control a flow of the gas refrigerant through the second side of the subcooler. A gas temperature sensor and a gas pressure sensor are configured to measure a temperature and pressure of the gas refrigerant. A liquid temperature sensor is configured to measure a temperature of the subcooled liquid refrigerant. A controller is configured to calculate a superheat of the gas refrigerant based on the measured temperature and measured pressure of the gas refrigerant and may compare the calculated superheat to a superheat threshold. If the calculated superheat is less than the superheat threshold, the controller may close the expansion valve. If the calculated superheat is equal to or greater than the superheat threshold, the controller may operate the expansion valve using a feedback control technique to drive the temperature of the subcooled liquid refrigerant to a subcooled liquid temperature setpoint.

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.

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.

A controller for a refrigeration system includes a processing circuit having one or more processors and memory. The processing circuit is configured to calculate a superheat of a gas refrigerant exiting a first side of a subcooler based on a measured temperature and a measured pressure of the gas refrigerant and compare the calculated superheat to a superheat threshold. In response to a determination that the calculated superheat is less than the superheat threshold, the processing circuit closes an expansion valve to restrict a flow of the gas refrigerant through a second side of the subcooler. In response to a determination that the calculated superheat is equal to or greater than the superheat threshold, the processing circuit operates the expansion valve to drive a temperature of a subcooled liquid refrigerant exiting the second side of the subcooler to a subcooled liquid temperature setpoint.

A refrigeration apparatus includes: a refrigerant circuit through which refrigerant circulates; a controller to execute a plurality of refrigerant shortage sensing functions of sensing a shortage of an amount of the refrigerant; and an input device through which an operation mode to be set is input into the controller. The operation mode includes: a first mode in which energy-saving performance is emphasized; and a second mode in which the refrigeration apparatus is permitted to operate in a range in which reliability is ensured. In accordance with the operation mode set through the input device, the controller determines which one of sensing results obtained by the refrigerant shortage sensing functions is enabled and which one of sensing results obtained by the refrigerant shortage sensing functions is disabled. When a sensing result determined to be enabled shows a refrigerant shortage, the controller gives a notification about the refrigerant shortage.

A controller for a refrigeration system includes a processing circuit having one or more processors and memory. The processing circuit is configured to calculate a superheat of a gas refrigerant exiting a first side of a subcooler based on a measured temperature and a measured pressure of the gas refrigerant and compare the calculated superheat to a superheat threshold. In response to a determination that the calculated superheat is less than the superheat threshold, the processing circuit closes an expansion valve to restrict a flow of the gas refrigerant through a second side of the subcooler. In response to a determination that the calculated superheat is equal to or greater than the superheat threshold, the processing circuit operates the expansion valve to drive a temperature of a subcooled liquid refrigerant exiting the second side of the subcooler to a subcooled liquid temperature setpoint.