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Effect of Heat exchanger’s Pressure Drops on the Thermal Efficiency of Brayton Cycles Complex Configurations with s-CO<inf>2</inf> Mixtures as Working Fluid

Abstract:

This work analyzes the impact that pressure drops have on the thermal efficiency of Brayton cycles that operate with mixtures based on supercritical carbon dioxide (s-CO2/C2H6, s-CO2/CH4, s-CO2/Kr, and s-CO2/SF6). As a working fluid. Four complex configurations were studied: recompression with two and three reheating’s (RCC-2RH), (RCC-3RH); recompression with main compressor intercooling with two and three reheating's (RCMCI-2RH), (RCMCI-3RH). The performance of the cycle at the design point is evaluated as a design parameter. The methodology applied to calculate it is obtained by establishing values of the heat total recuperator conductance (UAtotal) between 5 and 25 MW/K. The main conclusion of this work is that the cycle’s efficiency has increased due to mixtures compared to pure CO2 as the working fluid. The s-CO2/Kr mixture with a mole fraction of 65/35 is the one with the best performance since the efficiency values obtained are between 4% and 5% points above the standard fluid (pure s-CO2). Additionally, this blend has a lower cost per net capacity compared to pure s-CO2. RCC configurations are 6.73% lower, while in RCMCI configurations, it is 2.3% lower.