Dynamic simulation and exergy analysis of an Organic Rankine Cycle integrated with vapor compression refrigeration system

Abstract

Organic Rankine Cycle (ORC) has consistently been demonstrated to be one of the most effective and reliable methods for extracting low-grade waste heat energy. The objective of this study is to analyze the integrated vapor compression refrigeration system (VCRS)-ORC system. A custom and verified dynamic model is built using MATLAB-Simulink. The methodology used by the dynamic model is to vary the system parameters of the VCRS system for 150 pairs of VCRS-ORC refrigerant combinations to calculate the Coefficient of Performance (COP), exergy efficiency, and exergy destruction for the integrated system. For dynamic simulation, the VCRS load, evaporator, and condenser temperatures are varied from 1 TR to 10 TR, 0 degrees C to 10 degrees C, and 45 degrees C to 60 degrees C, respectively. The best performance is obtained for the R141b-R1234ze(Z) refrigerant pair for ORC and VCRS respectively, since a maximum system overall exergy efficiency of 33.045 %, a maximum net COP of 4.593, and the least exergy destruction of 2.591 kW is obtained. The net COP increases from 3.9 to 5.5 as the evaporator temperature rises; the turbine work decreases from 84.5 W to 78.5 W. The integrated VCRS-ORC system has a 10.62 % higher COP than the VCRS alone for the best refrigerant pair.