Working fluid selection based on critical temperature and water temperature in organic Rankine cycle

Abstract

This paper examines the thermal performance of working fluids in the entire evaporation temperature region up to near-critical temperature of working fluids in the organic Rankine cycle (ORC). The variation and tendency of the net power output with water temperature and correlated with the critical temperature of working fluids is investigated. Four characteristic curves of the net power output at particular water temperature (Tw_turn, Tw_app, Tw_tran and Tw_up) and their temperature difference (ΔT_turn=Tw_turn-Tcr, ΔT_app=Tw_app-Tcr) are obtained to evaluate the working fluids. The curve at “applicable water temperature (Tw_app)” is a demarcation to differentiate the net power output from low to high. The “upper water temperature (Tw_up)” is an upper limit of the water temperature to yield the higher net power output. A relation is built that the suitable water temperature is within the Tw_app and Tw_up of the working fluid.