In this paper, effect of the heaters' clearance on mixed convective cooling performance in a discretely heated horizontal duct is examined. Tests are carried out for a constant value of the modified Grashof number ($G{r}_{Dh}^{\text{*}}=$1.15$\times$10⁷), and for Reynolds numbers ($R{e}_{Dh}$) between 792 and 3,962. In the analysis, surface to surface radiation and wall conduction are coupled with convective heat transfer. Experiments involve measurements of surface temperatures and air velocity while ANSYS Fluent is used to conduct numerical simulations. Variations of the local surface temperatures, hot spot temperature, global conductance ($C$) and effective Nusselt number ($N{u}_{eff}$) with Reynolds number ($R{e}_{Dh}$) are presented. Finally, it is disclosed that up to 10.77% reduction in the hot spot temperature and an improvement of up to 20.84% in the system's global conductance can be achieved with an increase in the clearance.

在本文中，研究了加热器间隙对离散加热水平管道中混合对流冷却性能的影响。对修改的Grashof数的恒定值进行测试（$G{\mathrm{[R}}_{dH}^{\text{*}}=$1.15$\times$10 ⁷），以及雷诺数（$\mathrm{[R}{Ë}_{dH}$）介于792和3,962之间。在分析中，表面到表面的辐射和壁传导与对流传热耦合。实验涉及对表面温度和空气速度的测量，而ANSYS Fluent用于进行数值模拟。局部表面温度，热点温度，整体电导的变化（$C$）和有效的Nusselt数（$ñ{ü}_{ËFF}$）与雷诺数（$\mathrm{[R}{Ë}_{dH}$）。最后，据披露，随着间隙的增加，热点温度最多可降低10.77％，系统的整体电导率最多可提高20.84％。