Exergy maximization of cascade refrigeration cycles and its numerical verification for a transcritical CO2–C3H8 system

Analysis of an endoreversible two-stage cascade cycle has been implemented and optimum intermediate temperature for maximum exergy and refrigeration effect have been obtained analytically. Further, the heat reservoir temperatures has been optimised independently. A comprehensive numerical model of a transcritical CO2–C3H8 cascade system was developed with intent to verify the theoretical results. It is seen that the simulation results agree well for optimal TL but deviate modestly from the theoretical optimum of TH. It has also been observed that system performance improves as TH increases and unlike theoretical predictions, no optimal TH is present within feasible working temperatures.