Organic Rankine Cycle (ORC), Waste Heat Recovery, Scroll Expander, R245fa
An organic Rankine cycle (ORC) test setup has been constructed to investigate high-temperature waste heat recovery from a stationary internal combustion engine. In particular, an experimental study of a subcritical ORC architecture working with a high temperature heat source is performed to evaluate the feasibility of employing an ORC to recover west heat from small-scale internal combustion engines (~10 kW). The affordability of such a system for the given application has a significant impact on the cycle design. The ORC test setup consists of a diaphragm pump, a plate heat exchanger as regenerator, a novel micro-tube evaporator, an air-cooled condenser, a scroll-type expander, and R245fa as working fluid. Three expander prototypes, Oldham ring orbiting, idler shaft orbiting, and spinning scroll, have been considered and a comparison of their performance for this application is presented. Focus is given to constraining the high-side temperatures of R245fa to minimize oil breakdown while decreasing exergy destruction in the evaporator. The cycle performance is evaluated for varying thermal inputs, expander types, and refrigerant superheating values.