connectable on the input side to the output of condenser 1 as shown in fig2 a partial flow of the condensed or cooled refrigerant can be withdrawn via a line 13 having a relief valve f arranged therein from the condenser or gas cooler 1 and line 2 respectively and can be evaporated in heat transfer means e 1 by way of the refrigerant to be cooled which is fed to heat transfer means e 1 via line 2 u2032 the evaporated partial refrigerant flow then is fed via line 14 to a compressor 6 u2032 which is associated with the compressor unit 6 described hereinbefore and which preferably performs sucking on at a higher pressure level in the same the evaporated partial refrigerant flow then is compressed to the desired final pressure of compressor unit 6 as an alternative to the afore mentioned additional compressor 6 u2032 it is also possible to make use of multi cylinder compressors and to then deliver the amount of throttling vapour to be sucked off to one or several cylinders of each compressor at a higher pressure level by way of the heat transfer means e 1 the refrigerant flow to be pressure relieved in the intermediate relief device a preferably is cooled to such an extent that the amount of throttling vapour of the pressure relieved refrigerant is minimized as an alternative or in addition thereto the amounts of throttling vapour arising in collector 3 may also be sucked off at a higher pressure level via line 12 as well as line 15 shown in broken outline by means of compressor 6 u2032 fig3 illustrates an embodiment of the refrigeration circuit according to the invention and of the inventive method of operating a refrigeration circuit in which.