第一个也是最广为人知的关于垂直表面和水平管层流膜冷凝的研究是Nusselt（1）。他假设冷凝膜中的惯性和对流效应可以忽略不计，汽液界面处的剪切力可以忽略不计，温度等于饱和温度。这项关于椭圆水平圆柱体上或其内部冷凝的研究也是基于努塞尔的方法。结果也是倾斜管内冷凝的第一近似值，因为如图1所示，穿过管的垂直面产生一个椭圆，其短轴等于管直径，长轴等于直径除以倾斜角的余弦。这种近似适用于冷凝液仅在椭圆平面上流动的情况。 引文:阿什雷学报，第83卷，第2部分，哈利法克斯，北卡罗来纳州

The first and most widely known study of laminar film condensation for both vertical surfaces and horizontal tubes was that of Nusselt (1). He assumed that inertia and convection effects in the condensate film were negligible and that at the vapor-liquid interface the shear forces were negligible and the temperature equal to the saturation temperature.This study of condensation on or within an elliptical horizontal cylinder is also based on Nusselt's approach. The results are also a first approximation for condensation within an inclined tube since a vertical plane passing through a tube, as shown in Fig. 1, yields an ellipse having a minor axis equal to the tube diameter and a major axis equal to the diameter divided by the cosine of the angle of inclination. This approximation is valid to the extentthat the condensate flows only 1n the plane of the ellipse.