Patent ID: 7644593

Claim:
CO 2 refrigeration circuit ( 2 ) for circulating a refrigerant in a predetermined flow direction, comprising in flow direction a heat-rejecting heat exchanger ( 4 ), a receiver ( 10 ) having a liquid portion ( 12 ) and a flash gas portion ( 14 ), and subsequent to the receiver ( 10 ) a medium temperature loop ( 20 ) and a low temperature loop ( 24 ), wherein the medium and low temperature loops ( 20 , 24 ) each comprise in flow direction an expansion device ( 26 , 28 ), an evaporator ( 30 , 32 ) and a compressor ( 46 , 38 ), the refrigeration circuit ( 2 ) further comprising a liquid line ( 16 ) connecting the liquid portion ( 12 ) of the receiver ( 10 ) with at least one of the medium and low temperature loops ( 20 , 24 ) and having an internal heat exchanger ( 54 ), and a flash gas line ( 50 ) connecting the flash gas portion ( 14 ) of the receiver ( 10 ) via the internal heat exchanger ( 54 ) with the inlet of the low temperature compressor ( 46 ), wherein the internal heat exchanger ( 54 ) transfers in use heat from the liquid flowing through the liquid line ( 16 ) to the flash gas flowing through the flash gas line ( 50 ).