| 摘要 |
PROBLEM TO BE SOLVED: To reduce heat of hot gas consumed in heating of a liquid refrigerant, and shorten the time of defrosting operation by performing operation changeover to defrosting operation after preheating operation for raising refrigerant condensation temperature is performed for a predetermined time before starting of the defrosting operation when fresh air temperature is a set value or lower. SOLUTION: When a command from a timer 21 is inputted into preheating control means 22 after a predetermined time from predetermined defrosting starting time, the preheating control means 22 compares set temperature inputted from a temperature set means 23 with fresh air temperature inputted from a fresh air temperature sensor 18, and if the former is lower than the latter, execution of the preheating operation is determined. Herein, if a freezer is interrupted, it is started, and simultaneously a command is outputted to condensation fans 6A, 6B to reduce the rotational speeds and the number of machines. The preheating operation is performed for a predetermined time prior to the defrosting operation and then refrigerant condensation temperature is raised so that temperature of a liquid refrigerant is also raised. Thus, there is reduced heat of hot gas consumed in heating of the liquid refrigerant. |
