Refrigeration cycle apparatus

A refrigeration cycle apparatus comprising:

• a compressor configured to compress and discharge a working fluid;
• a condenser configured to condense the working fluid discharged from the compressor;
• a refrigerant-refrigerant heat exchanger provided with a condensed fluid passage in which the working fluid flowing out of the condenser flows and a low-pressure passage in which the working fluid having a lower pressure than that of the working fluid flowing in the condensed fluid passage flows, and configured to exchange heat between the working fluid flowing in the condensed fluid passage and the working fluid flowing in the low-pressure passage;
• a first expansion device configured to reduce a pressure of the working fluid flowing out of the condensed fluid passage of the refrigerant-refrigerant heat exchanger;
• an evaporator configured to evaporate the working fluid, the pressure of which is reduced by the first expansion device;
• an optical sensor provided on a pipe connecting between an outlet of the condensed fluid passage of the refrigerant-refrigerant heat exchanger and the first expansion device, and provided with an irradiator configured to irradiate the working fluid flowing in the pipe with light and a detector configured to detect a light transmitting through the working fluid;
• and
• a controller configured to obtain a concentration of a component included in the working fluid based on a detection result of the optical sensor.