Organic rankine cycles (ORCs) for waste heat utilization

Considering the thermodynamic performance, economic performance, and environmental performance simultaneously, the thermo-environmental optimization for a series dual-pressure organicRankine cycle (STORC)and a cascaded organic Rankine cycle (CORC)has been investigated. The effects of key operating parameters on the thermal and economic performance of the system were analyzed. Based on a 3 kW ORC experimental prototype, the heat exchanger performance of different mixtures has been studied and compared. Five different proportions of working fluids were selected, respectively, R123, 0.33R123/0.67R245fa, 0.5R123/0.5R245fa, 0.67R123/0.33R245fa, and R245fa. The comparison between the experimental test and simulation result without considering the pressure drop was addressed. Results indicate that R245fa/R152a is the best candidate working fluids for CORC LT-Loop. The evaporator heat transfer coefficients of R245fa are highest, followed by the R245fa/R123 mixture and while R123 shows the lowest evaporator heat coefficients. The measured thermal efficiency of 0.67R123/0.33R245fa is the highest, which is 7.33% and the maximum simulated thermal efficiency is 14.55%.