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.