Patent ID: 8393172

Claim:
A heat pump drying machine which comprises an accommodation room for accommodating a drying target and a heat pump having a refrigeration circuit constructed by a compressor, a radiator, an expansion device and an evaporator and in which the drying target is dried in the accommodation room by making refrigerant discharged from the compressor operated at a first operation frequency flow through the radiator, the expansion device and the evaporator and by circulating air in an air blowing path so that the air flows from the radiator to the evaporator via the accommodation room and returns to the radiator, wherein the heat pump drying machine has a first dry operation mode for operating the compressor at a first operation frequency and a second dry operation mode for operating the compressor at a second operation frequency, the second operation frequency being lower than the first operation frequency, and the heat pump drying machine further comprises an operation control unit that switches the operation mode of the compressor between the first operation mode and the second operation mode by switching the operation frequency of the compressor between the first operation frequency and the second operation frequency, and when a defrosting operation is executed on the evaporator during the second dry operation mode, the operation control unit increases the operation frequency of the compressor from the second operation frequency up to an operation frequency enough to remove frost occurring in the evaporator so that heat is entrapped in the air blowing path and the frost occurring in the evaporator is removed.