Patent ID: 7690213

Claim:
A waste heat utilization device comprising: a refrigeration cycle having a compressor which draws a low-pressure refrigerant flowing from a side of an evaporator for cooling air, compresses the drawn refrigerant to have a high temperature and high pressure, and discharges the compressed refrigerant toward a condenser in which refrigerant is cooled and condensed; a Rankine cycle using the condenser in common with the refrigeration cycle, the Rankine cycle including a pump for pumping and sending refrigerant, and an expansion unit which expands refrigerant sent by the pump and heated by waste heat from a heat generating unit so as to recover a mechanical energy; and a control unit which controls operation of the refrigeration cycle and the Rankine cycle, wherein: the control unit performs a continuation control of the Rankine cycle, in which the Rankine cycle is continuously operated regardless of an operation state of the compressor, when a load of the refrigeration cycle is lower than a predetermined load; and the control unit performs an intermittent control of the Rankine cycle, in which the Rankine cycle is intermittently operated in accordance with the operation state of the compressor when the load of the refrigeration cycle is higher than the predetermined load, wherein, in the intermittent control, a quantity of mechanical energy recovered by the expansion unit is larger than a quantity of driving energy required by the compressor for the operation of the Rankine cycle.