Air-conditioning apparatus

An air-conditioning apparatus comprising:

• a refrigeration cycle formed by connecting, with a refrigerant pipe, a compressor, a first refrigerant flow switching device, a first heat exchanger, a refrigerant passage of a second heat exchanger that exchanges heat between a refrigerant and a heat medium, an expansion device that corresponds to the second heat exchanger, and a second refrigerant flow switching device, the refrigerant being a non-azeotropic refrigerant mixture of a low-boiling refrigerant component and a high-boiling refrigerant component;
• a heat medium circuit formed by connecting, with a heat medium pipe, a heat medium passage of the second heat exchanger and a use-side heat exchanger, the heat medium circuit being configured to circulate the heat medium different from the refrigerant;
• a first temperature detecting device;
• a second temperature detecting device, the first temperature detecting device and the second temperature detecting device being disposed before and after the expansion device;
• a first pressure detecting device;
• a second pressure detecting device, the first pressure detecting device and the second pressure detecting device being disposed before and after the expansion device;
• and
• a computing device configured to calculate a composition of the refrigerant circulating in the refrigeration cycle on the basis of detection results of the first temperature detecting device, the second temperature detecting device, and the first pressure detecting device or the second pressure detecting device,
• wherein the computing device
• tentatively sets a value of a composition of the low-boiling refrigerant component of the refrigerant circulating in the refrigeration cycle within a range of 50 to 74 wt % and outputs a physical property table corresponding to the set value,
• calculates a quality of the refrigerant flowing out of the expansion device on the basis of
• an inlet liquid enthalpy calculated on the basis of the physical property table and a temperature from the first temperature detecting device, and
• a saturated gas enthalpy and a saturated liquid enthalpy calculated on the basis of the physical property table and temperature information from the second temperature detecting device,
• calculates a liquid-phase concentration and a gas-phase concentration of the refrigerant flowing out of the expansion device on the basis of a temperature and a pressure of the refrigerant flowing out of the expansion device, and
• calculates a further value of the composition of the low-boiling refrigerant component of the refrigerant circulating in the refrigeration cycle on the basis of the quality calculated from the tentatively set value of the composition of the low-boiling refrigerant component of the refrigerant circulating in the refrigeration cycle, the liquid-phase concentration, and the gas-phase concentration.