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 T-L but deviate modestly from the theoretical optimum of T-H. It has also been observed that system performance improves as T-H increases and unlike theoretical predictions, no optimal T-H is present within feasible working temperatures. (C) 2006 Elsevier Ltd and IIR. All rights reserved.