According to one embodiment, it preferentially executes, if the starting conditions for defrosting of each air conditioner are met chronologically close to each other, the defrosting operation with respect to the air conditioner starting condition for defrosting of which is earliest among the air conditioners without waiting for a time when the starting condition for defrosting thereof is met.

A defrost method for a heat pump system includes running the heat pump system in a heating mode to provide heat to an enclosed space and determining if an outdoor temperature is less than an outdoor threshold temperature. Responsive to a determination that the outdoor temperature is below the outdoor threshold temperature, determining if a calibration state has been previously run. Responsive to a determination that the calibration state has not been previously run, running the heat pump system in the calibration state. Responsive to a determination that the calibration state has been previously run, determining if a temperature difference between a temperature of an evaporator coil of the heat pump system and the outdoor temperature exceeds a temperature threshold value. Responsive to a determination that the temperature difference between the evaporator coil and the outdoor temperature is greater than the temperature threshold value, running the heat pump system in a defrost state.

A refrigerant leakage determination system capable of detecting leakage of refrigerant without requiring complicated processing is provided. A refrigerant leakage determination system is a refrigerant leakage determination system of a refrigeration cycle apparatus that includes a refrigerant circuit including a heat-source-side heat exchanger and has, as operating modes, a normal mode in which the heat-source-side heat exchanger is caused to function as an evaporator and a defrosting mode in which the heat-source-side heat exchanger frosted during a normal operation is defrosted. The refrigerant leakage determination system includes a processor configured to acquire defrosting information regarding a relationship between a normal operation period and the number of defrosting operations, and memory that stores the defrosting information. The processor is further configured to determine, based on the acquired defrosting information, leakage of refrigerant in the refrigerant circuit.

A control method and device for a refrigerator, and the refrigerator. The refrigerator comprises at least two compartments. The control method comprises: acquiring a compartment currently requesting cooling; after detecting and confirming a first set time, the compartment currently requesting cooling not being cooled, determining a currently cooled compartment, and interchanging currently set valve body rotation angles corresponding to the compartment currently requesting cooling and the currently cooled compartment requesting cooling. The present disclosure may solve the problem in which a refrigerator cannot be cooled normally due to a connection error between the capillary tube and a solenoid valve during the production of a multi-system refrigerator, and reduces the refrigerator repair rate, improves the refrigerator production efficiency, and reduces fabrication costs.

The present disclosure discloses a control method for an air conditioning system. The air conditioning system at least includes a compressor, a heat exchanger and a throttle device. The operation phase of the air conditioning system at least includes a start-up phase and a stable phase. The control method includes an action that in the start-up phase, the operating time of the compressor is set as t, when t is greater than 0 and less than 60s, an operating frequency F of the compressor is controlled to be less than 75 Hz, and a frequency rise speed per second V.sub.f of the compressor is controlled to be less than 1.25 Hz/s.

A refrigeration cycle apparatus includes a plurality of outdoor units. Each of the plurality of outdoor units includes an outdoor heat exchanger, a compressor, and a sensor to detect the quantity of refrigeration oil in the outdoor unit. A controller has a first operation mode in which a part of the plurality of outdoor units is operated and another outdoor unit is stopped; and a second operation mode in which all of the plurality of outdoor units are operated. In the first operation mode, when the operating time of an operating outdoor unit exceeds a prescribed time and the quantity of refrigeration oil in the compressor of the operating outdoor unit is equal to or larger than a prescribed quantity, the controller stops the operating outdoor unit and makes a switch to bring a stopped outdoor unit of the plurality of outdoor units into operation.

A method for increasing working gas flow rate through gas bearings of a free piston, gamma configured Stirling heat pump to avoid failure of the gas bearings while maintaining thermal cooling power. The Stirling heat pump lifts heat from a storage chamber and has pistons that are driven in reciprocation at an operating frequency by linear electric motors. A temperature control maintains a steady state storage chamber temperature by sensing storage chamber temperature and modulating piston amplitude. The invention comprises (a) driving the pistons with linear electric motors that are driven by a variable frequency, AC power source; (b) sensing the pistons' amplitude of reciprocation; and (c) if the sensed piston amplitude is less than a selected piston activation amplitude, increasing the frequency of the AC power source to increase the Stirling heat pump's operating frequency. That decreases thermal cooling power which causes the temperature control to increase piston amplitude.

Disclosed is a system for detecting a refrigerant leak in a refrigeration system, wherein a system controller is configured to: execute leak test cycles that include executing a first phase (T1-T2) of transferring refrigerant charge to the evaporator, a second phase (T2-T3) of transferring refrigerant charge to the condenser, and a third phase (T3-T4) of transferring refrigerant charge to the evaporator, determine a reference leak detection cycle time (LDCTREF) by determining a time from a beginning of the second phase (T2) in a first test to an end of the third phase (T4) in the first test, and setting LDCTREF to the time, determine a second leak detection cycle time (LDCT2nd) by determining a time from a beginning of the second phase (T2) in the second test to a second end of the third phase (T4) in the second test, and setting LDCT2nd to the time, determine if a refrigerant leak exists, and communicate the determination.

An HVAC system includes a compressor, condenser, and evaporator. A sensor measures a value associated with the refrigerant in the condenser or the evaporator, and a controller is communicatively coupled to the compressor and the sensor. The controller determines, based on an operational history the compressor, that pre-requisite criteria are satisfied for entering a sensor validation mode. After determining the pre-requisite criteria are satisfied, an initial sensor measurement value is determined. Following determining the initial sensor measurement value, the compressor is operated according to a sensor-validation mode. Following operating the compressor according to the sensor-validation mode for at least a minimum time, a current sensor measurement value is determined. The controller determines whether validation criteria are satisfied for the current sensor value. In response to determining that the validation criteria are satisfied, the controller determines that the sensor is validated.

Heat transfer devices and systems are provided for the rapid cooling of pulsed high-powered, high-flux devices using flash boiling. Such devices comprise at least two fluidly connected chambers and a heat exchanger in thermal communication with a heat source. A flash boiling event is actively triggered at a location close to the heat source by rapid depressurization of the chamber containing a multi-phase coolant. This boiling process allows for high heat transfer rates from the heat source into the chambers due to the latent heat of vaporization, which results in the rapid cooling of the heat source. A porous medium may also be positioned within a chamber of the device to enhance boiling nucleation and extended surface heat transfer. Methods of rapidly cooling pulsed heat sources are also provided using the devices and systems hereof.