exceeds the low side pressure of the supercritical pressure refrigerant fluid 40 by a factor within the range of from 1 5 to 3 0 the higher supercritical pressure refrigerant fluid 50 is cooled in gas cooler 100 by indirect heat exchange with air or by another utility or heat transfer fluid the energy extracted within gas cooler 100 is represented by energy stream q 100 resulting higher supercritical pressure refrigerant fluid 10 is passed from gas cooler 100 to internal heat exchanger 110 wherein it is cooled by indirect heat exchange with warming refrigerant fluid as will be more fully described below the cooled higher supercritical pressure refrigerant fluid is passed in stream 20 from heat exchanger 110 to an expansion device which in the embodiment illustrated in the figure is a dense phase turboexpander 120 wherein it is expanded to a low side pressure which is still higher than the critical pressure of the refrigerant fluid energy derived from this expansion is shown as q 120 alternatively the expansion device may be an isenthalpic valve the expansion of the refrigerant fluid through the expansion device further cools the refrigerant fluid which emerges from the expansion device as cold temperature supercritical pressure refrigerant fluid in stream 30 the critical temperature of carbon dioxide is 88 u00b0 f when the refrigerant fluid comprises carbon dioxide the temperature of the cold temperature supercritical pressure refrigerant fluid in stream 30 is less than the critical temperature and generally is within the range of from 0 to 60 u00b0 f the critical temperature of nitrogen is u2212 230 u00b0 f when the refrigerant fluid comprises nitrogen the temperature of the cold temperature supercritical pressure refrigerant fluid in stream 30 is higher than the critical temperature and generally within.