Experimental investigation on organic Rankine flash cycle with high- and low-stage scroll-expanders for thermal power generation

Organic Rankine cycle (ORC) is often used for low-medium grade thermal power generation, but its performance is low mainly due to the sensible heat used to rise the temperature of the working fluid is relatively in the process of complete evaporation. Hence, organic Rankine flash cycle (ORFC) is proposed in order to reduce evaporation irreversible loss. Previous studies indicate that the ORFC is advanced in power generation but without any experimental validation. An ORFC experiment setup was built with R245fa as the working fluid. The main objective of this paper is to validate the so-called theoretical advancement by experimental test. The characteristics include heat transfer, pressure drop, power generation and isentropic efficiency, etc. The experiment is based on the heat source temperature/mass flow rate of 85 °C/0.3639 kg/s and the heat sink temperature/mass flow rate of 12 °C/0.4389 kg/s. Experimental results validate that the tested power output of the ORFC is 28.23 % higher than that of ORC under the rated working condition. An increase in the heat source temperature improves the matching between the evaporation, expansion, condensation, pressurization and flash processes from the rated working condition, resulting in an increase of power output. Both over- and under-expansion cause the actual expansion ratio to deviate from the rated design value, the isentropic efficiencies of the high-pressure expander and the low-pressure expander tested are 54.68 – 64.87 % and 45.23–56.92 %.