Refrigeration apparatus including lubrication of compressor with refrigerant

A refrigeration apparatus comprising:

• a main refrigerant circuit including a positive displacement compressor, a condenser, an expansion valve, and an evaporator, through which a refrigerant circulates successively in a closed loop circulation;
• a lubrication refrigerant line connected to the main refrigerant circuit between the condenser and the expansion valve or to the condenser, in which circulates a portion of the refrigerant of the main refrigerant circuit and connected to the compressor for lubrication of said compressor with the refrigerant;
• wherein the lubrication refrigerant line comprises, upstream from the compressor:
• a throttle valve adapted to vary the lubrication refrigerant flow entering the compressor,
• a downstream pressure detector configured to measure refrigerant pressure downstream the throttle valve and upstream the compressor,
• a downstream temperature detector configured to measure refrigerant temperature downstream the throttle valve and upstream the compressor,
• and wherein the refrigeration apparatus comprises a control unit adapted to determine a state of the refrigerant in the lubrication refrigerant line using the measurements of the downstream pressure detector and the downstream temperature detector, and configured for controlling the throttle valve on the basis of at least the pressure downstream the throttle valve and the state of the refrigerant in the lubrication refrigerant line.