Working fluid selection of Organic Rankine Cycles

Abstract

Organic Rankine Cycles (ORCs) are identified as one of the best candidates to generate electricity from low-grade heat sources. ORCs operate on low temperatures and low pressures with comparative to conventional Rankine Cycles. Therefore, organic fluids or refrigerants can be used as the working fluids for ORC applications, instead of water, which is more suitable for high-pressure and high-temperature applications. The performance and the system design of the ORC system are entirely dependent on the working fluid, and hence, working fluid selection for ORCs is utmost important for a particular application, i.e. solar thermal, geothermal or waste heat recovery. Performance of the ORCs for seven (07) working fluids: R-134a, R-245fa, Benzene, Methanol, Ethanol, Acetone and Propane (R-290) have been studied during this work. Results of the study show that Benzene and Methanol based ORC systems perform more efficiently with comparative to the other working fluids considered in the analysis and, they require lower fluid mass flowrates per unit of power generation relative to other fluids used in the analysis.