In this paper, 20kW Ocean Thermal Energy Conversion(OTEC) with vapor-vapor ejector is proposed. vapor-vapor ejector is to increase pressure as like pump without electricity. By installing the vapor-vapor ejector in system, the needed working fluid rate and evaporation capacity are less than not installing. And then, The system efficiency of OTEC is better than not. The performance analysis is conducted for optimizing the system with HYSYS simulation program. The procedure of performance analysis includes outlet pressure of high turbine, the mass flow ratio of working fluid at separator and nozzle diameters of vapor-vapor ejector. When the nozzle diameters of vapor-vapor ejector are varied properly, the performance of vapor-vapor ejector is highest. After optimizing this proposed OTEC system with ejector, the increasing rate of efficiency of proposed OTEC system with ejector is about 15% comparing with basic OTEC system. From these results, It is necessary to set the pressure ratio, mass flow ratio, nozzle diameters in ejector to increase the efficiency of proposed OTEC system. Additionally, in this study, 12 refrigerants were selected for performance comparison. 12 refrigerants applied to proposed OTEC system and were optimized in system. And the results of performance comparison are system efficiency, APRe, APRc, TPP and mass flow rate of working fluids, pressure recovery rate of ejector. In case of system efficiency, R134a is the highest efficiency among 12. But, in case of APRe and APRc, R744 is the optimized to minimize the size of heat exchangers. In TPP, R717 is the most suitable to decrease the comsumption of pump work. And R717 needs the least amount of mass flow rate of working fluids to make 20kW at turbine.
As mentioned above, with respect to factors of performance comparison, the optimized working fluid is different. So It is necessary to select the optimized working fluid which is suitable respectively.