AIR CONDITIONING AND HEATING SYSTEM

摘要

Disclosed is a cooling and heating system for improving heating efficiency. According to the present invention, the flow rate of a refrigerant returning to an evaporator (condenser in a cooling and defrosting operation modes) is controlled by the repetitive phase changes of a refrigerant gas in the heating operation mode of a heat pump unit so that: the accumulation of frost on the evaporator can be prevented; and the heating operation of a cooling and heating unit can be stably performed by preventing the generation of excessive condensation when the pressure of the refrigerant is dropped by outdoor air temperature below a certain temperature, wherein the frost is accumulated on the evaporator when the temperature of a condensed refrigerant is dropped by outdoor air and/or the pressure of the refrigerant is raised; and the generation of the excessive condensation is prevented by driving a fan.