Air-conditioning apparatus

An air-conditioning apparatus, comprising:

• a refrigeration cycle connecting, by refrigerant pipes, a compressor having an injection port, an indoor heat exchanger, a first pressure reducing device, a second pressure reducing device, and an outdoor heat exchanger;
• an injection circuit connecting between the injection port and a branching portion arranged between the first pressure reducing device and the second pressure reducing device of the refrigeration cycle;
• a third pressure reducing device arranged in the injection circuit;
• an internal heat exchanger configured to exchange heat between refrigerant flowing between the branching portion and the second pressure reducing device and refrigerant depressurized by the third pressure reducing device;
• and
• a controller configured to control at least an opening degree of the second pressure reducing device,
• the refrigeration cycle being operable in a heating operation in which the indoor heat exchanger serves as a condenser and the outdoor heat exchanger serves as an evaporator,
• the controller being configured to control an opening degree A of the second pressure reducing device to satisfy Relation A+C=B×Gr, where A represents the opening degree of the second pressure reducing device, C represents an opening degree of the third pressure reducing device, B represents a coefficient determined based on a discharge pressure and a suction pressure of the compressor, and Gr represents a refrigerant circulating amount in the refrigeration cycle.