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 50^oC. 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 350^oC and 400^oC, respectively. Moreover, exergetic performance analysis reveals better performance of RBC with CO₂-C₇H₈ binary mixture.