A flash tank economizer includes a sensor for sensing a condition indicative of pressure in the flash tank, and when that pressure is found to equal or exceed the critical pressure of the particular refrigerant being used, a controller responsively closes a valve in the economizer vapor line to shut off the economizer. A sensor is also provided to sense the pressure at the compressor mid-stage, and if that pressure is found to exceed the pressure in the flash tank, the controller causes the flow control device to function so as to prevent the flow of refrigerant from the compressor mid-stage to the flash tank. Provision is also made for selectively draining refrigerant from the flash tank to reduce the pressure therein from a supercritical to a subcritical condition.

A carbon dioxide refrigerant vapor compression system and method of operating that system are provided. The refrigerant vapor compression system includes a compression device, a flash tank receiver disposed in the refrigerant circuit intermediate a refrigerant heat rejection heat exchanger and a refrigerant heat absorption heat exchanger, and a compressor unload circuit including a refrigerant line establishing refrigerant flow communication between an intermediate pressure stage of the compression device and the refrigerant circuit at a location downstream of the refrigerant heat absorption heat exchanger and upstream of a suction inlet to the compression device, and a unload circuit flow control device disposed in said unload circuit refrigerant line. In response to at least one system operating parameter sensed by at least one sensor, the controller selectively positions the unload flow control device to maintain the refrigerant vapor compression system operating below a preselected high pressure limit.

A refrigeration device includes a radiator, an evaporator, a compressor, a heater and a control device. The radiator causes a refrigerant to radiate heat. The evaporator causes the refrigerant to evaporate. The compressor compresses the refrigerant circulating between the radiator and the evaporator. The heater heats lubricating oil in the compressor. The control device controls the heater so that an oil temperature of the lubricating oil in the compressor reaches an oil temperature target value obtained by adding a predetermined temperature to saturation temperature of the refrigerant in the compressor.

A method of operating an air conditioning system including: operating a refrigerant compression device at a demand speed to circulate refrigerant through a refrigeration circuit; monitoring, using a temperature sensor, a temperature of external ambient air; monitoring, using a pressure sensor, a pressure of the refrigerant within the refrigerant circuit; detecting, using a controller, when the temperature of external ambient air is greater than a selected temperature; detecting, using the controller, when the pressure of the refrigerant is greater than a selected pressure; and reducing the speed of the refrigerant compression device to a selected speed for a first duration of time when the temperature of external ambient air is greater than the selected temperature and the pressure of the refrigerant is greater than the selected pressure.

A system and method are provided including a system controller for a refrigeration or HVAC system having a compressor rack with a compressor and a condensing unit with a condenser fan. The system controller monitors and controls operation of the refrigeration or HVAC system. A rack controller monitors and controls operation of the compressor rack and determines compressor rack power consumption data. A condensing unit controller monitors and controls operation of the condensing unit and determines condensing unit power consumption data. The system controller receives the compressor rack power consumption data and the condensing unit power consumption data, determines a total power consumption of the refrigeration or HVAC system, determines a predicted power consumption or a benchmark power consumption for the refrigeration system, compares the total power consumption with the predicted power consumption or the benchmark power consumption, and generates an alert based on the comparison.

A method for controlling a refrigeration system having a compressor, heat rejecting heat exchanger, expansion valve and heat absorbing heat exchanger circulating a refrigerant in series flow, the heat absorbing heat exchanger in thermal communication with working fluid, the method includes obtaining an expansion valve position set point; using a feedback control loop to generate a controlled expansion valve position; obtaining a rate of change of an operating parameter of the system; using the rate of change of the operating parameter to generate an adjustment; modifying the controlled expansion valve position using the adjustment; and controlling the expansion valve using the modified controlled expansion valve position.

A two-stage refrigerant compressor and an operation method thereof are disclosed. The two-stage refrigerant compressor (10) includes: a housing (1); a first compressor module (2) having first screw rods (21) and a first motor (22) driving the first screw rods (21) to rotate; a second compressor module (3) having second screw rods (31) and a second motor (32) driving the second screw rods (31) to rotate; an adjustment mechanism (4) having a first slide valve (41) and a second slide valve (42); a middle pressure sensor (51) configured to acquire a current middle pressure; and a processor configured to receive data of the current middle pressure, control rotating speeds of the first motor (22) and the second motor (32), and control locations of the first slide valve (41) and the second slide valve (42).

A heat pump system may include: a compressor configured to compress a refrigerant; a refrigerant-water heat exchanger configured to perform heat exchange between the compressed refrigerant and inlet water; an expansion valve configured to expand the refrigerant condensed in the refrigerant-water heat exchanger; an outdoor heat exchanger configured to perform heat exchange between the refrigerant expanded in the expansion valve and outdoor air; a high pressure sensor configured to detect a high pressure saturation temperature of the refrigerant compressed in the compressor; an inlet water temperature sensor configured to detect a temperature of water flowing into the refrigerant-water heat exchanger; a condensation temperature sensor configured to detect a temperature of the refrigerant condensed in the refrigerant-water heat exchanger; an outdoor temperature sensor configured to detect an outdoor temperature; and a controller including at least one processor, comprising processing circuitry, individually and/or collectively, configured to: determine a reference supercooling degree of the refrigerant based on detection of outdoor temperature by the outdoor temperature sensor and inlet water temperature by the inlet water temperature sensor and an operating frequency of the compressor, determine a current degree of supercooling of the refrigerant based on detection of pressure saturation temperature by the high pressure sensor and condensation temperature by the condensation temperature sensor, and determine whether the refrigerant leaks by comparing the reference supercooling degree and the current degree of supercooling.

A system and method are provided including a system controller for a refrigeration or HVAC system having a compressor rack with a compressor and a condensing unit with a condenser fan. The system controller monitors and controls operation of the refrigeration or HVAC system. A rack controller monitors and controls operation of the compressor rack and determines compressor rack power consumption data. A condensing unit controller monitors and controls operation of the condensing unit and determines condensing unit power consumption data. The system controller receives the compressor rack power consumption data and the condensing unit power consumption data, determines a total power consumption of the refrigeration or HVAC system, determines a predicted power consumption or a benchmark power consumption for the refrigeration system, compares the total power consumption with the predicted power consumption or the benchmark power consumption, and generates an alert based on the comparison.

A sensor supply tube assembly is provided for disposition within a compressor outlet through which a main flowpath is defined and a sensor port transversely coupled to the compressor outlet. The sensor supply tube assembly includes first and second tubes. The first tube is formed to direct main flowpath fluid from the compressor outlet and through a portion of the sensor port and includes first and second ends disposed within the sensor port and the compressor outlet, respectively, and a curved section interposed between the first and second ends. The second tube includes a sleeve tightly fittable between the first end and the sensor port and a base. The base has an exterior surface from which the sleeve extends and which is disposed and configured to non-rotatably abut with an interior surface of the compressor outlet.