Abstract
This paper proposes working fluid selection for Rankine cycle driven by heat source with small temperature difference. The heat source temperatures are set at 80℃ and 40℃ for higher and lower, respectively. Four conditions for working fluid selection are made. 1.Working fluid is natural working fluid. 2.Critical temperature is higher than 40℃. 3.Condensation pressure is higher than atmospheric pressure. 4.Gradient of saturate vapor line on T-s diagram is positive or zero. As a result, it is found that hydrocarbons were proper for the present cycle. In addition, regarding selected working fluids, the effect of adiabatic efficiencies both turbine and pump on the thermal efficiency is discussed.
