Thermodynamic Analysis of Organic Flash Cycle By R600a/R601a Mixtures

Organic flash cycle (OFC) can effectively use low‐ and medium‐temperature heat sources. The non‐isothermal phase change characteristic of R600a/R601a mixtures can improve the thermal match between the cycle and heat sink. In this study, a thermodynamic model of the OFC system was proposed. The OFC system was driven by heat source temperatures of 100–200 °C. R600a/R601a mixtures were selected as the working fluids. The effects of the mole fraction of the mixtures and the heat source temperature on the net power output, cycle efficiency, and second‐law efficiency were investigated. The exergy destruction in the component was also discussed. Results showed that when the heat source temperature was 100–180 °C, the relative increments in the net power outputs of the mixture systems were 0.62–5% compared with that of the R601a system. At 190–200 °C, the R601a system demonstrated the largest net power output. A characteristic temperature (Tct) was also observed. When THS,in ≤ Tct, the net power output was mainly affected by the thermal match between the cycle and the heat sink, flashing process destruction, and low‐pressure throttle valve destruction. When THS,in > Tct, the net power output was mainly affected by the thermal match between the cycle and the heat sources.