REFRIGERANT CIRCULATION SYSTEM

PROBLEM TO BE SOLVED: To obtain a refrigerant circulation system for controlling the throttling amount of a throttling mechanism based on the detection temperature of delivery gas or suction gas of a compressor in which deterioration of efficiency at an appropriate delivery or suction temperature is suppressed by employing low solubility refrigerating machine oil and refrigerant being encapsulated in the compressor. SOLUTION: A frequency varying unit 6 controls the r.p.m. of a compressor and optimal opening of an expansion valve and an optimal delivery or suction temperature determined by experiment, or the like, are prestored in a control section 71. When the output frequency from the frequency varying unit 6 is varied, an optimal opening of the expansion valve corresponding to the varied frequency is selected at the control section 71. The control section 71 delivers a valve opening command signal corresponding to the selected value and controls the opening of an electronic control expansion valve 4 to match 'with a target value through a valve drive section 72. Refrigerating machine oil and refrigerant having low solubility are encapsulated in the compressor 1. Delivery or suction temperature can be controlled appropriately because the effect of fluctuation in the hydraulic pressure from an optimal value determined by experiment, or the like, is suppressed.