Optimization Study on Regenerative Organic Rankine Cycle (ORC) with Heat Source of Low-Grade Steam

Abstract

Aiming at improving the performance of Organic Rankine Cycle (ORC) system with low-grade steam as heat source, this work studied and optimized the main operating parameters of the ORC system. The effects of evaporation temperature, superheat degree, condensation temperature and regenerator pinch temperature difference on the system performance were obtained. The optimization for the operating parameters is based on the indicators of specific net power output, waste heat pollution, cycle exergy efficiency, and total UA value (the product of overall heat transfer coefficient and heat transfer area of heat exchanger). The results show that the increase of the evaporation temperature and the superheat degree, and the decrease of the condensation temperature and regenerator pinch temperature difference can improve general system performance but lead to weaker economic performance. The optimal evaporation temperature, superheat degree, condensation temperature and regenerator pinch temperature difference are determined as 139°C, 4°C, 36°C and 8°C, respectively, reaching net power output of 114.73 kW, exergy efficiency of 37.10%. Besides, it is indicated that the regenerative ORC system can reach 13.6% additional net power output compared to the ORC system without the regenerator.