Working fluid pair selection of a dual-loop organic Rankine cycle (DORC)

The thermodynamic property of the working fluid is an significant factor influencing the performance of the organic Rankine cycle (ORC). In order to recover the waste heat of the exhaust, the engine coolant and the residual heat of the cycle after expansion which are in different temperature grades, based on a dual-loop organic Rankine cycle (DORC), this paper selects five working fluid pairs including water-Ethanol water-R123 water-R1270 water-R134a and water-R290 to study the system performance. Results show that the water-Ethanol system obtains the optimal thermal efficiency, while the water-R123 system obtains the maximum net output power. The volume expansion ratio of the second loop in the water-Ethanol system reaches the maximum, and two-stage or multistage expander is needed for water-Ethanol system.