A novel comprehensive evaluation methodology of organic Rankine cycle for parameters design and working fluid selection

In order to improve the overall performance of organic Rankine cycle (ORC) systems, a novel evaluation method using the combination of grey relational method and entropy theory was presented. Based on a comprehensive evaluation indicator, which is constituted by 4 indicators in terms of thermodynamics, economy and environment, system performance was evaluated under different turbine inlet pressure and pinch point temperature difference. Besides, a performance comparison of six different working fluids was conducted. The results show that ORC system can achieve a better comprehensive performance at lower pinch point temperature difference in the evaporator. And there is an optimal turbine inlet pressure, which is significantly influenced by the inlet temperature of exhaust gas, to minimize the value of comprehensive evaluation index (CEI). As a low global warming potential (GWP) working fluid, butane produces the best comprehensive performance for exhaust temperature range of 443-483 K, and R1233zd(E) gives the highest value of CEI in exhaust temperature range of 483-513 K. Additionally, R1234yf is recommended for exhaust temperature lower than 443 K.