Thermodynamic Performance Improvement of Recompression Brayton Cycle Utilizing CO2-C7H8 Binary Mixture

Abstract

The article deals with the energy and exergy performance analyses of supercritical carbon dioxide recompression Brayton cycle (S-CO2 RBC). This cycle is known to offer maximum efficiency when operating near the critical point of CO2, which is possible in low ambient temperature environment but not in warm or hot ambient conditions. CO2-C7H8 binary mixture is used to improve the thermodynamic performance of the cycle for warmer ambient conditions. The percentage of C7H8 in the mixture is selected according to cycle’s minimum temperature, which is assumed 50oC. When using CO2-C7H8 binary mixture, the analysis shows that the thermal efficiency of the cycle is improved by nearly14.5% and 8% for turbine inlet temperatures of 350oC and 400oC, respectively. Moreover, exergetic performance analysis reveals better performance of RBC with CO2-C7H8 binary mixture.