PARAMETRIC OPTIMIZATION AND PERFORMANCE ANALYSIS OF GEOTHERMAL ORAGANIC RANKINE CYCLE USING ZEOTROPIC MIXTURE OF R600A/DME AS WORKING FLUID

Abstract

Organic Rankine cycle is preferred to convert low temperature geothermal energy to electricity. The working fluid selection and system parameters optimisation are the main approaches to improve the performance of ORC system. Zeotropic mixtures are showing promise as ORC working fluids due to better match between the working fluid and the heat source/sink temperatures. This study optimises the evaporator inlet temperature of mixture (R600a/DME) for various mass fractions to maximize the net work output and compare the thermal efficiency and exergetic efficiency of system for geothermal water temperature of 393K. Irreversibility in each component of system and mass flow rate of mixture are also found in this analysis by varying mass fraction of R600a. After doing analysis, it was found that R600a/DME (0.8/0.2) gives the maximum net work output corresponding to 343K inlet temperature to evaporator. Among all selected proportions, R600a/DME (0.6/0.4) has both maximum thermal efficiency and maximum exergetic efficiency corresponding to 373k inlet temperature to evaporator. Irreversibility present in evaporator is minimum for mass fraction 0.6 of R600a. Mass flow rate of mixture increases with mass fraction of R600a upto 0.6 and then become approximately constant.