Numerical Analysis on Characteristics of Supercritical CO2-Xe Mixture Convective Heat Transfer Based on Heat Transfer Resistance

Supercritical CO2-Xe mixture has a potential application prospect in the innovative supercritical Brayton cycle system. In contrast to supercritical CO2, heat transfer capability of supercritical CO2-Xe mixture has not been widely concerned. The characteristics of supercritical CO2-Xe mixture flow and heat transfer in a vertical circular tube with an internal diameter of 8 mm are explored through numerical method. Then, the effects of Xe mass fraction ω(Xe), heat flux, and mass flux on the heat transfer of the mixture are discussed. Based on the perspective of pseudo-phase transition during supercritical fluid crossing pseudo-critical temperature, the fluid domain within the circular tube is divided into a two-layer structure: a vapor-like film near the tube wall and a liquid-like region in the core, with a transition occurring at the pseudo-critical temperature Tpc. The heat transfer mechanism is illustrated based on the heat transfer resistance caused by vapor-like film region and liquid-like region, and the relative importance of the above factors on the heat transfer. It is found that the heat transfer resistance of vapor-like film, which is significantly higher than that of the liquid-like, is the key factor controlling the convective heat transfer coefficient and occurrence of heat transfer deterioration. Furthermore, the larger the ω(Xe) is, the higher the heat transfer resistance of the CO2-Xe mixture at the same operating parameters, so that the heat transfer capability is worse. The research result is of significance to the design of heat transfer equipment for supercritical CO2-Xe mixture. transfer equipment for supercritical CO2-Xe mixture. ©2024 Chin.Soc.for Elec.Eng.