FREEZER AND METHOD FOR ADJUSTING ITS FREEZING CAPACITY

PURPOSE:To get an efficient maximum freezing capacity of a freezer by a method wherein the freezer is provided with a suction pressure and a discharging pressure control means for a compressor for use in controlling an amount of refrigrant in a cycle and capable of changing a compressing level while a compression ratio of the refrigerant compressor installed in the cycle being kept constant or substantially constant. CONSTITUTION:When an expansion turbine inlet temperature is kept constant, an expansion turbine processing amount is proportional to an expansion turbine inlet pressure, i.e., a compressor discharging pressure and at the same time a compressor air volume is proportional to the suction pressure. Accordingly, if the compression ratio of compressor 2 is kept constant, it becomes possible to make the compressor processing air volume when the suction pressure is reduced coincide with the expansion turbine processing amount when the discharging pressure is reduced and thus it is also possible to get a compressor driving power and a cold in correspondence with the case in which a required freezing load is reduced under a normal operation. That is, when a pre-cooling operation is carried out, a valve 11a if herium gas feeding circuit 11 is opened, herium is fed from a tank 10 into a main circuit 9, a discharging pressure is increased and a pressure level in the main circuit 9 is increased. A cooling capacity in a freezer 1 is taken out in its maximum amount so as to shorten the pre-cooling time.