Film Boiling Heat Transfer for High Temperature Liquid Sodium

基于层流边界层理论，得到了考虑液体过冷度和圆柱体辐射影响的水平圆柱体池膜沸腾换热理论模型的严格数值解。给出了理论模型的近似解析解，该近似解析解在较宽的条件范围内与各种物性差异较大的液体的严格数值解吻合较好。获得了系统压力、液体过冷度、表面过热度和圆柱体直径等较大范围内水平圆柱体在不同液体中的池膜沸腾换热实验数据。通过对近似解析解稍加修正，使之与实验值更接近，建立了一个新的关联式。通过对基于层流边界层理论的理论解稍加修改，得到了较大直径的水平圆柱体、垂直板、水平板和球体的过冷池膜沸腾换热关联式，使之与非金属液体的实验值更符合。将现有的钠液球和液钾水平板上的池膜沸腾换热数据与关联值进行了比较，结果表明，当液体的辐射吸收系数有效地统一时，每种构型的关联式都能很好地描述实验数据。这远远高于静态表面的0.16左右的值。在钠中进行了薄膜沸腾实验，以明确吸收系数有效增加的原因。这些结果将在不久的将来发表。

A rigorous numerical solution of a theoretical model based on laminar boundary layer theory for pool film boiling heat transfer from a horizontal cylinder including the contributions of liquid subcooling and radiation from the cylinder was obtained. An approximate analytical solution for the theoretical model was also derived.The approximate analytical solution agreed well with the rigorous numerical solution for various liquids of widely different physical properties under wide ranges of conditions.Experimental data of pool film boiling heat transfer from horizontal cylinders in various liquids for wide ranges of system pressure,liquid subcooling, surface superheat and cylinder diameter were obtained. A new cor- relation was developed by slightly modifying the approximate analytical solution to agree better with the experimental data.Correlations for subcooled pool film boiling heat transfer from horizontal cylinders, vertical plates, horizontal plates and spheres with relatively large diameters were derived by slightly modifying theoretical solutions based on laminar boundary layer theory to accord better with experimental data for non-metallic liquids.Comparison of available pool film boiling heat transfer data on spheres in liquid sodium and the data on a horizontal plate in liquid potassium with the values derived from the correlations showed that the experimental data were described well by the correlation for each configuration when the radiation absorptivity of liquids were taken to be unity effectively, which was far higher than the value for a static surface of around 0.16.Film boiling experiment in sodium was performed to make clear the cause of the effective increase in the absorptivity. These results will be published in the near future.