PURPOSE: To catch usable time of a heat insulator to enable the heat insulator efficiently by a method wherein, during heat insulation, a remaining cooling volume of a cold accumulator is detected by a remaining cooling volume determining means based on a signal from a plurality of temperature detecting parts and detection values are displayed.
CONSTITUTION: After power source is drawn off, a heat insulating room 33 is heat insulated with melting latent heat of a cold accumulator 28 by circulating cooled air by a ventilation fan 30. The cold accumulator 28 melts from an upstream side to a downstream side with respect to a cold air flowing direction and temperatures of temperature detecting parts 53, 54 and 55 rise up in this order. A remaining cooling volume determining means 56 compares signals from the temperature detecting means 53 to 55 with an arbitrarily set temperature only when it is known from a signal from a power source supply determining means 43 that commercial power source is OFF, determines a remaining volume time, and catches a remaining cooling volume time by a remaining cooling volume display means 57 by pushing a remaining volume switch 58.
FUJIMOTO SHINJI
MASATOKI YOSHIBUMI
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