Air-conditioning apparatus with a plurality of indoor units and a cooling and heating mixed mode of operation

An air-conditioning apparatus comprising:

• a plurality of indoor units, wherein each indoor unit is configured to be installed inside a building at a position that allows the indoor units to condition air in a space to be air-conditioned and including a use-side heat exchanger;
• a relay unit configured to be installed in a space not to be air-conditioned and different from the space to be air-conditioned;
• and
• an outdoor unit configured to be installed in one of an outdoor space outside the building and a space inside the building communicating with the outdoor space,
• wherein the relay unit and the plurality of indoor units are connected to each other via a first heat transfer medium pipe in which a first heat transfer medium that transports heating energy or cooling energy flows,
• the outdoor unit and the relay unit are connected to each other via a second heat transfer medium pipe in which a second heat transfer medium that transports heating energy or cooling energy flows,
• the relay unit includes:
• a first compressor;
• a first refrigerant flow switching device;
• a plurality of first intermediate heat exchangers;
• a second refrigerant flow switching device associated with each of the plurality of first intermediate heat exchangers;
• a plurality of first expansion devices that depressurize a first refrigerant that shifts between two phases or turns into a supercritical state during operation;
• and
• a second intermediate heat exchanger, wherein
• the first compressor, the first refrigerant flow switching device, a refrigerant flow path in the plurality of first intermediate heat exchangers, the second refrigerant flow switching device, the plurality of first expansion devices, and a refrigerant flow path in the second intermediate heat exchanger are connected via a first refrigerant pipe in which the first refrigerant that shifts between two phases or turns into a supercritical state flows, to form a first refrigerant circuit,
• the first heat transfer medium is allowed to circulate through a heat transfer medium flow path in the plurality of first intermediate heat exchangers, a plurality of first heat transfer medium feeding devices that feed the first heat transfer medium, and the plurality of use-side heat exchangers, to form a first heat transfer medium circuit,
• cooling of the first heat transfer medium and heating of the first heat transfer medium are performed at the same time utilizing at least one of the first refrigerant flow switching device and the second refrigerant flow switching device,
• a first heat transfer medium flow switching device is provided between the plurality of first intermediate heat exchangers and the plurality of use-side heat exchangers,
• the first heat transfer medium flow switching device is configured to separately distribute the heated first heat transfer medium and the cooled first heat transfer medium to at least one of the indoor units, and
• the outdoor unit is configured to control a temperature of the second heat transfer medium,
• the air-conditioning apparatus further comprising a cooling and heating mixed operation mode in which, in the relay unit, heat is removed from or rejected to the second heat transfer medium utilizing evaporation heat or condensation heat of the first refrigerant, the first heat transfer medium is cooled with the evaporation heat of the first refrigerant in at least one of the plurality of first intermediate heat exchangers, and the first heat transfer medium is heated with the condensation heat of the first refrigerant in at least one of the rest of first intermediate heat exchangers,
• wherein both of a frequency of the first compressor and a flow rate of the second heat transfer medium flowing into the second intermediate heat exchanger are controlled in the cooling and heating mixed operation mode to:
• cause both of the evaporation temperature of the first refrigerant flowing in the refrigerant flow path for cooling the first heat transfer medium in the first intermediate heat exchanger and the condensation temperature of the first refrigerant flowing in the refrigerant flow path for heating the first heat transfer medium in the first intermediate heat exchanger to approach respective target values, or
• cause both of a temperature of the first heat transfer medium cooled in the first intermediate heat exchanger cooling the first heat transfer medium and a temperature of the first heat transfer medium heated in the first intermediate heat exchanger heating the first heat transfer medium to approach respective target values.