非均匀热流影响超临界二氧化碳流动换热数值研究

In some extreme conditions, heat flux with high density is non-uniformly distributed on the surface. To address this issue, this paper analyzed the influence of non-uniform heat flux on the flow and heat transfer characteristics of supercritical carbon dioxide by employing numerical calculation and analysis methods. Numerical simulations were sequentially performed to analyze the flow and heat transfer of supercritical carbon dioxide in a horizontal circular tube with a diameter of 4 mm under two sets of linear non-uniform heat flux conditions including the same total heat flux with different slopes, as well as different total heat fluxes with the same slope. The influence of the distribution of thermophysical properties and buoyancy lift on the convective heat transfer characteristics under linear non-uniform heat flux conditions was obtained. The simulation results show that the heat transfer of the upper wall near the entrance of the heating section under non-uniform heat flux conditions severely deteriorates compared with that under uniform heat flux. The maximum tube wall temperature under linear non-uniform heat flux is 1.66 times that under uniform heat flux. Furthermore, numerical simulations of flow and heat flux of supercritical carbon dioxide on a given actual surface heat flux boundary are carried out, and the maximum tube wall temperature at the entrance of the heating section is 3.41 times that at the outlet, while the ratio decreases to 1.50 when the flow direction changes. Relevant suggestions are offered for cooling solutions using supercritical carbon dioxide as a working medium.