during its passage through compressor 2 that is used to lubricate the bearings and rotors of compressor 2 from the compressor 2 refrigerant with entrained oil passes through a line 5 to a condenser 6 compressed gaseous refrigerant is cooled in the condenser transferred into a liquid phase with oil in mixture or solution as it passes in line 11 through an expansion valve not shown to evaporator 3 at the evaporator 3 an environment to be cooled is cooled by the refrigerant in the evaporator as is shown it is typical that liquid refrigerant 7 settles from the refrigerant in the evaporator this refrigerant 7 is typically lubricant or oil laden as a result of the oil entrained during the compression process and associated lubrication and a portion of the oil laden refrigerant is transferred via line 8 to lubricant still 128 described further below according to the principle of the present invention a portion of this lubricant is drawn off using an oil pump not shown and delivered to compressor 2 through line 13 for lubrication of bearings and rotors referring to fig2 an example of how oil enters the refrigerant during the compression process will be further described shown in fig2 is a screw compressor 10 that includes a rotor housing 12 containing intermeshing screw rotors 14 and 15 and bearings 17 on suction.