Parametric optimization and range analysis of Organic Rankine Cycle for binary-cycle geothermal plant

In this study, a thermodynamic model of Organic Rankine Cycle (ORC) system combined with orthogonal design is proposed. The comprehensive scoring method was adopted to obtain a comprehensive index to evaluate both of the thermodynamic performance and economic performance. The optimal level constitution of system parameters which improves the thermodynamic and economic performance of ORC system is provided by analyzing the result of orthogonal design. The range analysis based on orthogonal design is adopted to determine the sensitivity of system parameters to the net power output of ORC system, thermal efficiency, the SP factor of radial inflow turbine, the power decrease factor of the pump and the total heat transfer capacity. The results show that the optimal level constitution of system parameters is determined as the working fluid of R245fa, the super heating temperature of 10 °C, the pinch temperature difference in evaporator and condenser of 5 °C, the evaporating temperature of 65 °C, the isentropic efficiency for the pump of 0.75 and the isentropic efficiency of radial inflow turbine of 0.85. The order of system parameters' sensitivity to the comprehensive index of orthogonal design is evaporating temperature > isentropic efficiency of radial inflow turbine > the working fluid > the pinch temperature difference of the evaporator and the condenser > isentropic efficiency of cycle pump > the super heating temperature. This study provides useful references for selecting main controlled parameters in the optimal design of ORC system.