uid phase piping 6 may be held to the equilibrium pressure of about 7.5 Pa where R-134a is condensed at 7??? C. and the fuel regulation valve 28 is closed when the temperature of the R-134a as detected by the temperature sensor S13 falls below a predetermined level, for example 5??? C., as the R-134a is cooled by the heat exchanger 2 to become condensed and discharged into the liquid phase piping