Design optimization and performance analysis of a supercritical carbon dioxide recompression Brayton cycle based on the detailed models of the cycle components

Supercritical carbon dioxide Brayton cycle has emerged as a promising power cycle that features high efficiency, compact and simpler cycle layout, minimal impact on the environment and integration capability on a wide range of energy conversion applications. The cycle operates near the critical point of carbon dioxide where properties of the supercritical carbon dioxide fluctuate dramatically, therefore an accurate analysis of the cycle's performance will require detailed mathematical models of its components. In this context, a 10 MWe recompression supercritical carbon dioxide Brayton cycle has been analyzed using in-house cycle design point and off-design codes. In contrast to the previously adopted simplified component models, the employed codes utilize compressor and turbine mean line codes along with a detailed heat exchanger model to accommodate real design configurations of the cycle's components and variations in the thermophysical properties of the working fluid. Cycle design point analysis suggested that a superior performance could be achieved by selecting compressor inlet conditions close to the critical point of carbon dioxide. Moreover, cycle off-design results were also computed with and without adjusting the defined control variables. Computed results revealed that the cycle's performance could be enhanced significantly during off-design conditions by adjusting the defined control variables particularly if off-design values corresponded to compressor's higher inlet temperature and lower inlet pressure.