A heat pump apparatus includes: a compressor including a motor; an inverter that applies a desired voltage to the motor; a current detector that detects current flowing to the motor; a drive-signal generation unit that generates a drive signal for the inverter; a magnetic-pole position estimation unit that changes a voltage phase of a voltage command value for a high-frequency voltage, and estimates a maximum-heat-amount acquisition magnetic-pole position when the generation unit applies the high-frequency voltage to the motor to heat the compressor; a steady heating control unit that determines an amplitude and voltage phase of the voltage command value from the maximum-heat-amount acquisition magnetic-pole position and a defined necessary amount of heat when the generation unit applies the high-frequency voltage to the motor to heat the compressor; and a control switching determination unit that causes one of the estimation unit and the heating control unit to operate.

A refrigeration cycle apparatus includes; a refrigerant circuit in which a compressor, a heat-source-side heat exchanger, a first expansion device, a second expansion device, and a load-side heat exchanger are sequentially connected by refrigerant pipes and in which refrigerant is circulated; a controller that controls the refrigerant circuit; a bypass pipe extending from a liquid pipe between the first expansion device and the second expansion device toward a suction side of the compressor; a third expansion device provided at the bypass pipe to decompress the refrigerant that flows through the bypass pipe; and a refrigerant cooler provided at the bypass pipe and downstream of the third expansion device to cause heat exchange to be performed between the refrigerant decompressed by the third expansion device and heat generated from the controller.

A refrigeration cycle apparatus includes; a refrigerant circuit in which a compressor, a heat-source-side heat exchanger, a first expansion device, a second expansion device, and a load-side heat exchanger are sequentially connected by refrigerant pipes and in which refrigerant is circulated; a controller that controls the refrigerant circuit; a bypass pipe extending from a liquid pipe between the first expansion device and the second expansion device toward a suction side of the compressor; a third expansion device provided at the bypass pipe to decompress the refrigerant that flows through the bypass pipe; and a refrigerant cooler provided at the bypass pipe and downstream of the third expansion device to cause heat exchange to be performed between the refrigerant decompressed by the third expansion device and heat generated from the controller.

An oil return control method for a multi-split air conditioner and a system accomplishing the same includes: calculating an average exhaust pressure within an oil return period Pd_AVG; determining whether the average exhaust pressure Pd_AVG≥the set threshold Pd.sub.threshold; if Pd_AVG≥Pd.sub.threshold, maintaining the multi-split air conditioner working in heating mode to ensure an acceptable oil return performance without affecting the air conditioning effect of indoor unit in heating mode; if Pd_AVG<Pd.sub.threshold, switching the multi-split air conditioner to cooling mode, stopping a fan within those power-on indoor units and entering into a cooling oil return process and switching the multi-split air conditioner back to heating mode until the cooling oil return process ends.

Provided is a refrigeration machine provided with: a refrigeration cycle having a compressor, a condenser, an expander, an evaporator, and piping (12) which sequentially connects the compressor, the condenser, and the expander; and an acoustic device (13) having a space formation section (14) which has one end (14a) connected to the piping (12) and in which a space is formed, the acoustic device (13) also having a vibration body (20) which is affixed integrally to the other end of the space formation section (14) and which has a lower natural frequency than the space formation section (14).

Provided is a refrigeration machine provided with: a refrigeration cycle having a compressor, a condenser, an expander, an evaporator, and piping (12) which sequentially connects the compressor, the condenser, and the expander; and an acoustic device (13) having a space formation section (14) which has one end (14a) connected to the piping (12) and in which a space is formed, the acoustic device (13) also having a vibration body (20) which is affixed integrally to the other end of the space formation section (14) and which has a lower natural frequency than the space formation section (14).

A refrigeration cycle apparatus (1) is capable of performing a refrigeration cycle using a small-GWP refrigerant. The refrigeration cycle apparatus (1) includes a refrigerant circuit (10) and a refrigerant enclosed in the refrigerant circuit (10). The refrigerant circuit includes a compressor (21), a condenser (23), a decompressing section (24), and an evaporator (31). The refrigerant contains at least 1,2-difluoroethylene.

A refrigeration cycle apparatus (1) is capable of performing a refrigeration cycle using a small-GWP refrigerant. The refrigeration cycle apparatus (1) includes a refrigerant circuit (10) and a refrigerant enclosed in the refrigerant circuit (10). The refrigerant circuit includes a compressor (21), a condenser (23), a decompressing section (24), and an evaporator (31). The refrigerant contains at least 1,2-difluoroethylene.

A heat exchanger includes flat tubes, a header, and a refrigerant inlet. The header has a first plate, a second plate, and a third plate. The first plate has a ridge portion defining a tank space. The second plate has a first flow passage and a second flow passage. The first flow passage extends in such a manner that an area of the first flow passage coincides with an area of the tank space. The second flow passage extends in such a manner that an area of the second flow passage does not coincide with the area of the tank space. An upper portion of the first flow passage and an upper portion of the second flow passage are connected to each other via a first connecting flow passage. A lower portion of the first flow passage and a lower portion of the second flow passage are connected to each other via a second connecting flow passage. The third plate has a communicating hole that allows the first flow passage and each of the flat tubes to communicate with each other.

A heat pump system with a refrigerant flow path comprising, in the heating mode of operation: a compressor coupled to receive refrigerant from a heating mode first refrigerant stream and a heating mode second refrigerant stream of the refrigerant flow path; the condenser coupled to receive refrigerant from the compressor; and a heat exchanger for transferring heat between the heating mode first refrigerant stream and the heating mode second refrigerant stream, wherein the heating mode first refrigerant stream comprises: the first expansion valve coupled to receive refrigerant from the condenser; the first evaporator coupled to receive refrigerant from the first expansion valve; and the heat exchanger coupling the heating mode first refrigerant stream from the first evaporator to the compressor, wherein the heating mode second refrigerant stream comprises: the second expansion valve; the heat exchanger coupling the heating mode second refrigerant stream from the condenser to the second expansion valve; and the second evaporator being coupled to communicate refrigerant from the second expansion valve to the compressor, wherein the first evaporator is in a first air flow conduit with a first air inlet for receiving a first air flow, and the second evaporator is in a second air flow conduit coupled to receive the first air flow.