Abstract: In a case where a concentration of refrigeration oil detected by the concentration sensor is less than a first threshold value, the control device operates the heater such that a part of a refrigerant in a liquid state in the compressor is vaporized, and in a case where the concentration of the refrigeration oil detected by the concentration sensor exceeds a second threshold value greater than the first threshold value and a temperature of the refrigeration oil detected by the temperature sensor is less than a specified temperature, the control device operates the heater such that the refrigerant in the liquid state in the compressor is vaporized and the temperature of the refrigeration oil in the compressor is increased.

Abstract: An air conditioning apparatus includes: a refrigerant circuit that includes a compressor, an outdoor heat exchanger, an indoor heat exchanger, and a pressure reducing device, and that is configured to circulate refrigerant; a plurality of sensors configured to detect a state of the refrigerant circuit; and a controller configured to control the refrigerant circuit based on detection results of the plurality of sensors, and the controller is configured to compare a determination value that is obtained based on a detection value of a sensor selected from the plurality of sensors, with a threshold value that is obtained based on a detection value of a sensor selected from the plurality of sensors, and determine, based on a comparison result, whether or not a reference amount of refrigerating machine oil is stored in the compressor.

Abstract: A refrigeration cycle apparatus comprises: a compressor; a first heat exchanger; a second heat exchanger; a first decompressing apparatus; an oil separator; a first circulation pathway in which a refrigerant circulates in an order of the compressor, the first heat exchanger, the oil separator, the first decompressing apparatus, and the second heat exchanger; an oil-returned pathway connecting between the oil separator and a suction side of the compressor; a second decompressing apparatus provided in the oil-returned pathway; and a controller configured to control the first decompressing apparatus and the second decompressing apparatus. The controller is configured to set an operation mode to an oil collection mode by adjusting a degree of decompression of the first decompressing apparatus and a degree of decompression of the second decompressing apparatus when the refrigerant and a refrigerating machine oil flowing in the first circulation pathway are separated in the oil separator.

Abstract: An air conditioner is a refrigeration cycle apparatus in which incompatible oil is employed as refrigerating machine oil, and includes a compressor to compress refrigerant, a first heat exchanger to condense the refrigerant output from the compressor, a pressure reducing device to reduce a pressure of the refrigerant output from the first heat exchanger, and a second heat exchanger to evaporate the refrigerant output from the pressure reducing device and output the resultant refrigerant to the compressor. The second heat exchanger includes a heat transfer tube having a groove formed on an inner surface of the heat transfer tube. The groove of the heat transfer tube is formed such that an inner surface area of the heat transfer tube on a downstream side of the heat transfer tube is smaller than an inner surface area on an upstream side of the heat transfer tuber.