Thermodynamic performance and optimization of the helium-xenon Brayton cycle for gas-cooled micro-reactors

The gas-cooled micro-reactor Brayton cycle using helium-xenon working fluid holds significant potential for applications in distributed energy supply, power assurance in remote areas, and other fields. However, the system's thermodynamic performance under engineering constraints has not been sufficiently explored. This study developed thermodynamic models and identified the primary factors influencing cycle performance, including system parameters and working fluid properties. The effects of key parameters on system performance were investigated. The results indicated that an increased helium fraction within the helium-xenon working fluid leads to changes in physical properties, resulting in an increase in turbine output work, cycle specific power generation, and cycle efficiency. Additionally, lower pressure ratios and higher recuperation effectiveness enhance cycle efficiency but may lead to the reactor pressure vessel temperature exceeding the limit 823 K. Therefore, optimal thermal design schemes were obtained through dual-objective optimization, considering the reactor pressure vessel temperature constraint. For helium, 40 g center dot mol-1 helium-xenon, 80 g center dot mol-1 helium- xenon, and xenon working fluids, the cycle efficiencies of the optimal schemes under the reactor pressure vessel temperature constraint are 37.32 %, 36.16 %, 32.63 %, and 24.31 %, respectively. This study provides a reference for the design and optimization of gas-cooled micro-reactor Brayton cycle.