PURPOSE: To prevent a gaseous hydrate from being made coarse and a performance factor from being lowered by controlling a stepless capacitor control type compressor such that evaporator temperature of a cold storage device for producing a gaseous hydrate is kept unchanged by cooling a mixed fluid with the evaporator.
CONSTITUTION: Temperature of an evaporator 6 is detected by a sensor 20 in a cold storage operation and inputted to a controller 21. Corresponding thereto, a frequency needed to keep the temperature of the evaporator 6 unchanged is evaporated, and a compressor 22 is rotated at the number of revolutions corresponding to the foregoing frequency with the aid of an inverter 23 to provide a capacity thereof capable of keeping the temperature of the evaporator 6 unchanged. Accordingly, cooling capability of a freezer C can gradually be reduced in response to the production of a gaseous hydrate 16, and hence temperature of a mixed fluid 5 and the evaporator 6 can be kept unchanged irrespective of the advance of the production of the gaseous hydrate 16. Accompained therewith, evaporation pressure of a refrigerant of the evaporator 6 becomes also unchanged, so that power consumption of the compressor 22 can be prevented from being increased and hence the performance factor of the freezer C is also kept unchanged. Additionally, the gaseous hydrate 16 is prevented from being mad coarse.
ISAKA YASUO
YAMANAKA TOSHIHIKO
MIZUKAMI HARUNOBU
KOJIMA SUSUMU
MITSUBISHI HEAVY IND LTD