A vehicle air-conditioning apparatus is provided which is capable of expanding an effective range of a dehumidifying and heating mode to achieve comfortable vehicle interior air conditioning. A control device (controller) executes a dehumidifying and heating mode to let a refrigerant discharged from a compressor 2 radiate heat in a radiator 4, let a part of the refrigerant flow from a bypass circuit (refrigerant pipe 13F) to an indoor expansion valve 8, and let the residual refrigerant flow through an outdoor expansion valve 6. In the dehumidifying and heating mode, the control device has a state of controlling the operation of the compressor 2, based on a heat absorber temperature Te and executes a radiator temperature priority mode which enlarges a capability of the compressor when heat radiation in the radiator is insufficient.

A refrigeration apparatus (1) includes a main refrigerant circuit (2) including a positive displacement compressor (4), a condenser (6), an expansion valve (8), and an evaporator (10), through which a refrigerant circulates successively in a closed loop circulation, a lubrication refrigerant line (18) connected to the main refrigerant circuit (2) between the condenser (6) and the expansion valve (8) or to the condenser (6), in which circulates a portion of the refrigerant of the main refrigerant circuit (2) and connected to the compressor (4) for lubrication of said compressor (4) with the refrigerant, at least one lubrication refrigerant storing cavity (70) connected to the lubrication refrigerant line (18), the lubrication refrigerant storing cavity (70) being configured to store liquid refrigerant for lubrication of the compressor (4) said at least one lubrication refrigerant storing cavity (70) being provided within the compressor (4).

A system for controlling a capacity of a compressor includes a motor of the compressor including a main winding connected at a connection point to an auxiliary winding and a drive configured to control a speed of the motor. The system includes a first switch configured to selectively connect the main winding to either a first line voltage or a first output of the drive, a second switch configured to selectively connect the connection point to either a second line voltage or a second output of the drive, and a third switch configured to selectively connect the auxiliary winding to either a capacitor or a third output of the drive. The system includes a solenoid valve configured to selectively either operate in a first capacity or a second capacity. The system includes a control module configured to control the drive, the first switch, the second switch, and the third switch.

An air-conditioning unit that is able to suppress ignition at an electric heater even when leakage of refrigerant occurs while a low-GWP refrigerant is used is provided. In an outdoor unit (20) including a casing (60), a compressor (21) provided inside the casing (60) and configured to compress refrigerant containing 1,2-difluoroethylene, and a drain pan heater (54) provided inside the casing (60), an electric power consumption of the drain pan heater (54) is lower than or equal to 300 W.

A pumped refrigerant system can include a condenser, a pump coupled downstream of the condenser, an evaporator assembly coupled downstream of the pump, the condenser being coupled downstream of the evaporator assembly, and a refrigerant heating assembly coupled downstream of the pump, the condenser being coupled downstream of the refrigerant heating assembly. The refrigerant heating assembly can include a tank and a heating element coupled to the tank and configured to heat refrigerant within the tank. An input valve can be configured to selectively allow the pump to push refrigerant into the tank. An output valve can be configured to selectively inject heated refrigerant from the tank into plumbing upstream of the condenser.

In a refrigeration cycle apparatus, refrigerant circulates successively through a compressor, a condenser, an expansion valve, and an evaporator. The refrigeration cycle apparatus includes a detection unit, a heating unit, and a controller. The detection unit is configured to detect a temperature of refrigeration oil in the compressor. The heating unit is configured to heat the refrigeration oil. The controller is configured to operate the heating unit when the temperature detected by the detection unit is lower than a pour point of the refrigeration oil, and to stop the heating by the heating unit when the temperature detected by the detection unit reaches the pour point. Preferably, the heating unit includes a heater provided on an outer side of a compressor casing and at a lower portion of a motor unit.

To provide a defrost system capable of preferable defrosting and prevention of generation of icicles on a casing without installing a brine circuit. A defrost system includes a thermosiphon defrost circuit that is provided by being branched from a circulation line, in which, at the time of defrosting, a CO.sub.2 refrigerant staying inside a fin-tube heat exchanger repeats a two-phase change of a gaseous form and reliquefaction, and which forms a CO.sub.2 circulation path together with the fin-tube heat exchanger; electromagnetic opening/closing valves that are closed at the time of defrosting and set the CO.sub.2 circulation path to a closed circuit; and a first electric heater arranged above the thermosiphon defrost circuit so as to be adjacent to the thermosiphon defrost circuit, and naturally circulates the CO.sub.2 refrigerant in the closed circuit at the time of defrosting.

A heat pump includes an internal heat exchanger and a regulating device designed to bring the temperature of the working fluid at the outlet of a compressor to a specifiable minimum difference above the dew point at the same pressure. This allows the use of novel coolants in heat pumps, e.g., coolants having a low dew line slope of under 1000/kJ in the temperature-entropy diagram and characterized by very good safety and environmental properties.

A liquid level detector includes: a vertically-mounted accumulator configured to store refrigerant; a heater configured to heat the accumulator; a temperature detector configured to detect a surface temperature of the accumulator; a pressure detector configured to detect a pressure of the refrigerant in the accumulator; and a controller configured to detect a position of a liquid surface of the refrigerant in the accumulator based on a surface temperature of the accumulator detected by the temperature detector when the accumulator is heated by the heater, and a pressure of the refrigerant in the accumulator detected by the pressure detector.

An illustrative example refrigerant system includes a compressor configured to pressurize a refrigerant fluid. The compressor includes a sump portion. A heater is situated to heat at least the sump portion. A controller is configured to selectively operate the heater to apply heat to at least the sump portion while the compressor is off to establish and maintain a superheat condition in the compressor.