Refrigerant cycle system with ejector pump

A refrigerant cycle system, comprising:

• an evaporator that has a cooling capacity by evaporating refrigerant therein;
• a radiator for cooling refrigerant flowing from the evaporator;
• an ejector pump including a nozzle for converting a pressure energy of refrigerant to a speed energy thereof so that the refrigerant is decompressed and expanded, the ejector pump being disposed to suck refrigerant from a side of the evaporator and to discharge the sucked refrigerant toward the radiator by a refrigerant stream jetted from the nozzle;
• a compressor for compressing refrigerant, the compressor being disposed to suck refrigerant from the side of the evaporator and discharge the sucked refrigerant toward the radiator;
• and
• a heating unit for heating refrigerant to be introduced into the nozzle, wherein:
• the ejector pump and the compressor are disposed to select any one of a first mode where refrigerant circulates from the evaporator toward the radiator only by the ejector pump, a second mode where refrigerant circulates from the evaporator toward the radiator only by the compressor, and a third mode where refrigerant circulates from the evaporator toward the radiator by both the ejector pump and the compressor.