Refrigerant circulating system

A refrigerant circulating system comprising:

• a main refrigerant circuit for circulating mixture refrigerant, said main refrigerant circuit including a compressor, a directional control valve, a condenser, a first throttling device and an evaporator;
• a bypass circuit diverging from a point between a discharge portion of said compressor and said directional control valve, and connected through a composition detecting heat-exchanger and a second throttling device to a point between an intake portion of said compressor and said directional control valve;
• first temperature detecting means located to a point between said composition detecting heat-exchanger and said second throttling device, said first temperature detecting means detecting refrigerant temperature at an upstream of said second throttling device;
• second temperature detecting means located to a point between said composition detecting heat-exchanger and said second throttling device, said second temperature detecting means detecting refrigerant temperature at a downstream of said second throttling device;
• first pressure detecting means located at an intake side of said compressor, and for detecting a pressure of refrigerant at its located place;
• a composition calculating device for calculating a composition of mixture refrigerant on the basis of the detected refrigerant temperature and pressure;
• second pressure detecting means located at the discharge side of said compressor, and for detecting the pressure of refrigerant at its located place;
• and
• a main controller for controlling at least compressor speed or fan speed provided to said condenser or evaporator, on the basis of the calculated composition of refrigerant and detected pressure of refrigerant.