EXPANSION-VALVE CONTROL DEVICE, HEAT-SOURCE UNIT, AND EXPANSION-VALVE CONTROL METHOD

摘要

The degree-of-opening of an expansion valve is set to an appropriate degree-of-opening regardless of the load and external conditions for a heat-source unit. In a turbo refrigerator including a compressor that compresses a refrigerant; a condenser that condenses a compressed refrigerant by means of cooling water; an evaporator that evaporates a condensed refrigerant and also performs heat exchange between this refrigerant and cold water; and an expansion valve that causes a liquid-phase refrigerant retained in the condenser to expand, a expansion-valve control device (40) controls a degree-of-opening of the expansion valve (18). Also, the expansion-valve control device (40) calculates a degree-of-opening of the expansion valve (18) based on the difference between a target degree of a superheating for the refrigerant to be taken into the turbo compressor and a measured degree of superheating; calculates a degree-of-opening of the expansion valve (18) based on a planned CV value serving as an estimated value of a flow volume of the refrigerant that is allowed to pass through the expansion valve (18); and calculates an expansion-valve degree-of-opening command value from the above-described two types of the degree-of-opening calculated for the expansion valve (18).