신재생에너지 가변열원의 효율적 이용을 위한 유기랭킨 사이클 최적작동점에 관한 연구

Abstract

Organic Rankine cycle (ORC) has been widely used to convert renewable energy such as solar energy, geothermalenergy, or waste energy etc., to electric power. For a small scale output power less than 10 kW, turbo-expander is not widelyused than positive displacement expander. However, the turbo-expander has merits that it can operate well at off-design points. Usually, the available thermal energy for a small scale ORC is not supplied continuously. So, the mass flowrate should be adjustedin the expander to maintain the cycle. In this study, nozzles was adopted as stator to control the mass flowrate, and radial-typeturbine was used as expander. The turbine operated at partial admission. R245fa was adopted as working fluid, and supersonicnozzle was designed to get the supersonic flow at the nozzle exit. When the inlet operating condition of the working fluid wasvaried corresponding to the fluctuation of the available thermal energy, optimal operating condition was investigated at off-designdue to the variation of mass flowrate.