Comparative investigation of a subcritical ORC, supercritical ORC, and trilateral rankine cycle power plant for a heat source temperature of 210-250 oC

Abstract

The performance investigations of subcritical ORC, supercritical ORC, and trilateral Rankine cycle (TLC) power plants with the heat source temperatures of 210-250°C were conducted and compared in this study. Several working fluids were evaluated. A MATLAB code was developed and used in this study. The thermodynamic properties of the working fluids were calculated by using NIST REFPROP program. The justification of the code was validated with a result taken from the literature. The optimal operating conditions were searched using the golden-section technique. The maximum net output power of 141.72 kW was obtained when using the supercritical ORC plant with R141b as its working fluid and the heat source temperature was at 250°C. The corresponding cycle efficiency was 16.25%. When using the subcritical plant at the same heat source temperature, the maximum net output power of 133.40 kW and cycle efficiency of 15.70% are obtained when pentane is used as the working fluid. Furthermore, the net output power of 133.82 kW and cycle efficiency of 14.90% are obtained when using R141b as the working fluid in the TLC power plant. According to the off-design simulations, an appropriate adjustment of the working fluid flow rate can mitigate the variation of the net output power.