Correlation analysis based multi-parameter optimization of the organic Rankine cycle for medium- and high-temperature waste heat recovery

Abstract The present paper established a multi-parameter optimization model of the organic Rankine cycle (ORC) to recover medium- and high-temperature waste heat. The preliminary screening of 42 pure working fluids is completed according to the limitations of environment and safety requirements. Afterwards, the relationship between heat source temperature, working fluid physical properties, and system net output power are analyzed. It can be found that there is a parabola variation relationship between working fluid critical temperature and system net power output. When the net power output reaches its peak value, a further increase of working fluid critical temperature will causes the opposite effect. Furthermore, correlation analysis is introduce to investigate the variation relationship between system net output power and working fluid critical temperature, system evaporating temperature/pressure, and condensing temperature/pressure by different heat source temperatures is investigated in detail. Results show that it is not much effective to use a working fluid with great pressure ratio for the design of a high-efficiency ORC system. On the contrary, using working fluid with a high temperature ratio can always improve the system net power output. Besides, the working fluid specific heat difference/ratio, and the latent heat difference/ratio during the evaporation and condensation processes jointly influence the ORC output performance. As a result, the influence order of working fluid key properties to the system net power output is: temperature ratio＞pressure ratio＞latent heat＞specific heat.