Nusselt’s Theory of Film Condensation on Vertical Surface

In the above figure the condensation of vapor on a vertical plate has been shown. X- Axial co-ordinate which is measured downwards along the plate and y is the co-ordinate measured upward along the plate. The problem was first analyzed by Nusselt and there are several assumptions. These assumptions are,

-         

             Uniform plate temperature will be less than the saturation temperature of the vapor.

-          Vapor exerts no drag force on the condensate. 

-          Flow of the condensate is laminar.

-          Flow velocity is very low.

-          Properties of fluid are constant.

-          Liquid temperature distribution is linear because of pure conduction heat transfer across the condensate layer.

These assumptions are absolutely necessary to complete the analysis.