Thermodynamic study of main compression intercooling effects on supercritical CO₂ recompression Brayton cycle

Supercritical CO₂ recompression Brayton cycle has emerged as a promising power cycle for various types of power conversion systems. In order to seek further performance improvement of supercritical CO₂ recompression Brayton cycle, thermodynamic effects of main compression intercooling (MCIC) are investigated in this work. Mathematical models were developed for Supercritical CO₂ recompression Brayton cycle with MCIC. Two key variable parameters, i.e., compressor pressure ratio and pressure ratio distribution between two main compression stages (represented with RPR_MC,1), were optimized. Effects of working conditions on MCIC effects and the optimized parameters were investigated. A comprehensive comparison between cycles with and without MCIC was performed in four typical conditions from both design and off-design viewpoints. Results show that RPR_MC,1 is more predominant to cycle efficiency than compressor pressure ratio. 2.65% efficiency improvement can be obtained by the integration of MCIC in the reference conditions. The variations of working conditions impact MCIC effects on cycle efficiencies. The optimized results of compressor pressure ratio and RPR_MC,1 are affected by the variation of minimum temperature, maximum temperature and maximum pressure. In addition to cycle efficiency improvement, the integration of MCIC also shows potentials in costs saving and cycle robustness improvement.