Patent ID: 8186171

Claim:
Method for controlling an intermittently supercritically operating refrigeration circuit ( 2 ) for circulating a refrigerant in a predetermined flow direction comprising in flow direction a compressor ( 4 ), a heat-rejecting heat exchanger ( 10 ), a control valve ( 12 ) associated to the outlet ( 14 ) of the heat-rejecting heat exchanger ( 10 ) and a control ( 16 ) for controlling the control valve ( 12 ), wherein, in order to achieve a continuous regulation of the high-pressure of the refrigerant at the outlet of the heat-rejecting heat exchanger, the method comprises the following steps: (a) in the subcritical mode, controlling the control valve ( 12 ) so that a predetermined “subcritical pressure” ensuring a predetermined sub-cooling of the liquid refrigerant at the outlet ( 14 ) of the heat-rejecting heat exchanger ( 10 ) is maintained; (b) in the supercritical mode, controlling the control valve ( 12 ) so that a predetermined “supercritical pressure”, which is optimized for optimum efficiency, of the supercritical refrigerant at the outlet ( 14 ) of the heat-rejecting heat exchanger ( 10 ) is maintained; and (c) in a border mode in a border region next to the critical point, controlling the control valve ( 12 ) to maintain the outlet ( 14 ) of the heat-rejecting heat exchanger ( 10 ) at a “continuity pressure” which is determined on the basis of the predetermined “subcritical pressure” and the predetermined “supercritical pressure” of steps (a) and (b) and which continuity pressure continuously connects the subcritical pressure with the supercritical pressure.