Thermodynamic optimization and performance study of supercritical CO2 thermodynamic power cycles with dry cooling using response surface method

Abstract

This paper deals with thermodynamic optimization of supercritical CO2 recompression and partial cooling cycles operating at cycle maximum temperature of 680°C and maximum pressure of 250 bar. The primary goal to investigate the effects of variation in heat sink temperature (ambient air temperature), mass split fraction (X), and cycle minimum pressure (Pmin) on the thermal efficiency of the power cycles. Response surface method (RSM) is adopted to create a second-order polynomial equation in order to develop the relationship between cycle thermal efficiency and selected decision variables and to find global optimum cycle efficiency. In addition, classification of most influencing cycle parameter is carried out using ANOVA approach. In the case of a recompression cycle, the results demonstrate that heat sink temperature has the greatest impact on thermal efficiency, owing to low p-value and high F-value, followed by mass split fraction and minimum pressure. In a partial cooling cycle, the minimum pressure has the most significant impact on cycle thermal efficiency, followed by the mass split fraction and heat sink temperature. The global optimum combination for the recompression cycle is at heat sink temperature of 20°C, the mass split fraction of 0.3182, and a minimum pressure of 89 bar to obtain the highest thermal efficiency of 0.4963. In addition, the global optimum combination for partial cooling cycle is at heat sink temperature of 32.8 °C, mass split fraction of 0.34, and minimum pressure of 76 bar, which results in an optimum thermal efficiency of 0.4708.