Thermodynamic analysis and thermoeconomic optimization of organic rankine cycle

In this study, four different organic Rankine cycle (ORC) configurations originating from waste heat were designed and modeled. Comparative thermodynamic and thermoeconomic analyzes of ORC configurations were performed for seven different selected fluids. In addition, parametric analysis has been carried out on how increasing evaporation and condensation temperatures affect the thermodynamic and thermoeconomic performance parameters of the designed systems. In the study, the working fluid, evaporator temperature, condenser temperature, turbine efficiency, pump efficiency, superheat temperature and subcooling temperature were determined as controllable factors. Four important output parameters of the system were considered in the objective function. To ensure maximum thermal and exergy efficiency, minimum total system cost and unit cost of electricity produced by the system, the effect degrees and ratios of control factors were calculated. For this, Taguchi and ANOVA statistical analysis methods were used. To obtain the optimum result that will enable the output parameters to be realized simultaneously, the objective function of the multi-objective optimization problem was defined, and its solution was realized with the Taguchi-Grey Relational Analysis method. The best thermodynamic performance results for R141b, R123, R245fa, R600, R114 and R600a fluids were calculated for ORC with Feed Fluid Heater-Internal Heat Exchanger. The system that paid for itself in the shortest time among the four ORC configurations was the simple ORC system. As a result of Taguchi and ANOVA analysis, the factors that most affect the thermal efficiency of the system, the exergy efficiency, the total system investment cost, and the unit cost of the electricity produced were, respectively, the evaporator temperature, turbine efficiency, working fluid and working fluid. The combination that maximizes the objective function in the multi-objective optimization process is R123 working fluid, 145 oC evaporation temperature, 25 oC condensing temperature, 90% turbine efficiency, 90% pump efficiency, 2 oC superheat and 5 oC subcooling temperature.