Working fluid selection for a combined system based on coupling of organic Rankine cycle and air source heat pump cycle

Abstract

Abstract The performance of thermodynamic cycle strongly depends on the properties of working fluids. A gas-fuelled hot water system based on coupling of an organic Rankine cycle and an air source heat pump cycle (ORC-ASHP) was investigated in this paper. This system is integrated with a gas burner to provide heat for ORC. The power generated in ORC is used to drive the air source heat pump cycle. Comparisons on the system performance are presented for seven different organic working fluids, with emphasis on the effect of thermodynamic properties of the working fluids. In terms of fuel-to-heat efficiency, benzene, toluene and cyclohexane have better performance for the high temperature heat source. The results indicate that working fluids presenting higher decomposition temperatures shows a higher fuel-to-heat-efficiency. When benzene is used as working fluids, the fuel-to-heat efficiency reaches 161.7% and 139.47% to provide 50 °C and 65 °C hot water respectively.