Multi-objective optimization and improved analysis of an organic Rankine cycle coupled with the dynamic turbine efficiency model

Abstract

Considering the effect of variable turbine efficiency on organic Rankine cycle (ORC) system working fluid selection and parameters determination, a multi-objective optimization model which considered the thermodynamic performance and economic factors simultaneously was coupled with a dynamic turbine efficiency model. The Pareto optimal solutions of optimization with constant turbine efficiency and with variable turbine efficiency were compared, specific quantitative analysis of turbine efficiency on an ORC system is presented and sensitivity analysis of the heat source temperature was conducted. The results reveal that the variation of net power output between constant turbine efficiency and variable turbine efficiency is different, and the distribution of Pareto optimal solutions with constant turbine efficiency and with variable turbine efficiency is also different. With constant turbine efficiency, R245ca is the optimal working fluid. However, with variable turbine efficiency, R365mfc is the optimal working fluid. In specific quantitative analysis, it can be found that the difference in the optimization results is related to the working fluid properties. For R245fa, the variation of turbine efficiency significantly affects the distribution of the Pareto optimal solutions. However, for R365mfc, the variation tendency of turbine efficiency is gentle, which only leads to a small deviation in the optimization results.