Effects of Intermediate Pressure and Split Ratio on Supercritical Modified Recompression Cycles Performance

Abstract

Engineers and scientists are continuously in search of higher power system efficiencies. Among new ones, supercritical recompression carbon dioxide power cycle has been promising. In addition to the simple recompression cycle, modified versions of supercritical recompression carbo have been introduced. These modified versions are Recompression Reheating cycle, Recompression Partial Cooling cycle, Recompression Partial Cooling with Reheating cycle, Recompression Intercooling cycle, and Recompression Intercooling with Reheating cycle. This paper investigates performances of the modified recompression cycles by developing an extensive thermodynamic model for this purpose. For these analyses, many parameters such as isentropic efficiencies of compressors and turbines, effectiveness of energy exchangers, maximum and minimum pressures, and temperatures within the cycle have been kept constant. It is also assumed that the temperature of the source of energy is 600 °C. This temperature selection is based on the operational temperatures typical of current solar thermal, nuclear, and biomass/waste energy generation technologies. Parametric studies using intermediate pressure and split ratio have been done to determine the optimum values resulting in the maximum efficiencies of these cycles. The solution of the thermodynamic model requires solving simultaneous energy, entropy, and exergy balance equations. The results show three cycles have very close maximum efficiency. These are Recompression Reheating cycle, Recompression Intercooling with Reheating cycle, and Recompression Intercooling cycle having thermal efficiencies of 39.61%, 39.57%, and 39.49%, respectively. The Recompression Intercooling with Reheating cycle has the highest net-work among the above cycles when operating at their maximum thermal efficiencies.