Hydrocarbon working fluids for a Rankine cycle powered vapor compression refrigeration system using low-grade thermal energy

• An organic Rankine cycle powered vapor compression refrigeration system is studied.
• Four hydrocarbon refrigerants used as working fluids in the system are evaluated.
• The hydrocarbons considered here include propane, butane, isobutane and propylene.
• Effects of operating parameters on the system performance are also investigated.
• Butane is the best working fluid among the four selected hydrocarbons for the system.

As natural fluids, several hydrocarbons with excellent thermophysical properties are recognized as alternative refrigerants to chlorofluorocarbons, hydrochlorofluorocarbons and hydrofluorocarbons. In this paper, the hydrocarbons including propane, butane, isobutane and propylene as working fluids used in an organic Rankine cycle powered vapor compression refrigeration (ORC–VCR) system are analyzed and evaluated. With the overall COP and working fluid mass flow rate of per kW cooling capacity as key performance indicators, the results indicate that butane is the best refrigerant for the ORC–VCR system as the boiler exit temperature is between 60 and 90 °C, the condensation temperature varies from 30 to 55 °C and the evaporation temperature ranges from −15 to 15 °C. When the boiler exit temperature reaches 90 °C and the other input parameters are in typical values, the overall COP of the butane case reaches 0.470.