Abstract: An air-conditioning apparatus for heating or cooling a room, having a flow control or heat capacity control mechanism for conducting, when heating the room, at least one of the steps of: exerting energy onto the refrigerant; reducing heat exchanged between the air surrounding the evaporator and the refrigerant passing through the evaporator; and enlarging the opening of the expansion valve, thereby preventing the liquid refrigerant from flowing into the compressor, and efficiently conducting heating operation when the outside temperature is very low or when refrigerant circulation pipes are long.

Abstract: An air conditioning apparatus for heating and cooling a room, which has a four-way valve to reverse the flow of a refrigerant, thereby switching the operation mode, heating or cooling, and which has a bypass line for bypassing an inside heat-exchanger, a control valve for controlling the flow ratio of the refrigerant passing through the bypass line and the inside heat-exchanger, and a refrigerant-heating element disposed in a line between the control valve and the compressor, thereby, in the defrosting mode, melting the frost formed on endothermic fins without cooling the room and without a liquid return to the suction side of the compressor.