Heat exchanger and air conditioning apparatus

An air-conditioning apparatus comprising

• a heat exchanger, the heat exchanger comprising:
• a compressor configured to compress refrigerant;
• a condenser configured to cause heat exchange to be performed between air and the refrigerant compressed by the compressor;
• an expansion unit configured to expand the refrigerant subjected to the heat exchange at the condenser;
• and
• an evaporator configured to cause heat exchange to be performed between air and the refrigerant expanded by the expansion unit;
• wherein the condenser or the evaporator includes
• a plurality of fins;
• and
• a plurality of tubes inserted into the fins and configured to allow the refrigerant to flow in the tubes,
• wherein the tubes include
• first heat transfer tubes, each first heat transfer tube including grooves formed in an inner surface of the first heat transfer tube and having an inside diameter Da and a groove depth Ta, and
• second heat transfer tubes, each second heat transfer tube having a smoothed inner surface, having an inside diameter Db, and being connected to an associated one of the first heat transfer tubes,
• wherein Da−2×Ta=Db is satisfied, and
• wherein when the heat exchanger is the condenser, the refrigerant that flows in each of the first heat transfer tubes is in a gas-phase state or in a two-phase gas-liquid state, and the refrigerant that flows in each of the second heat transfer tubes is in a subcooled state.