initial cold air flow from the indoor heat exchanger caused by prolonged warm up naturally a person skilled in the art may easily smooth the characteristic of the q t curve in fig5 in the design of a refrigeration system simply by controlling with the control valve the amount of refrigerant injected into the compressor 1 in fig7 a further explanation is given using a pressure enthalpy diagram in winter the refrigeration starts with the cycle formation drawn in the dotted line trapezoid a 39 e 39 f 39 g 39 here the line jh and j 39 h 39 respectively represent the saturated liquid and saturated vapor lines of a refrigerant point f 39 indicates the state of a kilogram of the refrigerant upon issuance from the condenser of a simple conventional refrigeration system and point g 39 represents the state of said refrigerant after constant enthalpy expansion along line f 39 g 39 the liquid refrigerant passes through the evaporator changing its condition along line g 39 a 39 the evaporated gas refrigerant is then recompressed along line a 39 e 39 necessitating an expenditure of work per kilogram which in terms of heat units is equal to the projection k k 39 on the enthalpy axis the compressed refrigerant is then returned through the condenser to the state f and the cycle is ready to repeat during operation as the compressor gradually becomes warmed up the refrigeration cycle turns to a new higher formation namely the one shown by the trapezoid a e f g since in the early stage of the operation the aperture 12 is opened forming the gas refrigerant.