Small-Scale Organic Rankine Cycle Performance Using an Additional Heat Exchanger

Abstract

The Organic Rankine Cycle (ORC) power generation system is a unique approach to heat recovery which substitutes an organic fluid with a low boiling point for water. To improve its lower thermal efficiency and maximum power generation, an Internal Heat Exchanger (IHE) is proposed after the expansion scroll expander. Using a small-scale scroll expander ORC testing facility as the simulation model, this study analyzes the net thermal efficiency and energy consumption of the ORC system with and without the IHE under conditions of equivalent power output. While the working fluid's outlet temperature in the evaporator was adjusted from 70 to 130 degrees Celsius, the outlet condenser temperature was kept constant at 55, 60, and 65 degrees Celsius. In the numerical simulation of the small-scale ORC, five distinct working fluids, including R245fa, R123, R1233zd, n-Pentane, and R141b were assessed. The results indicated that R245fa had the largest recuperation effect on the working fluid, followed by n-Pentane, R1233zd, R123, and R141b, with a total thermal energy reduction of 3.34 kW, 2.63 kW, 2.06 kW, 1.9 kW, and 0.92 kW, respectively. In conclusion, the installation of IHE in ORC units leads to improved thermal efficiency and maximum power generation.