2. Heat Transfer During Condensation

Condensation is the phenomenon of vapor changing to liquid. There are two basic modes of condensation, namely, film condensation and dropwise condensation. During film condensation, vapor condenses in the form of a continuous liquid film over the condensing surface. During dropwise condensation, vapor condenses in the form of drops covering parts of the surface. Heat transfer coefficients during dropwise condensation are much higher than those during film condensation. Hence dropwise condensation is desirable. However, most common fluids condense in the film mode over ordinary metallic surfaces. Most of the condensers used in the industry today operate with film condensation. The mechanism of film condensation is well understood, and the rate of heat transfer during film condensation can be predicted with reasonable accuracy in most cases. Much research has been and is being done to develop durable heat exchangers with dropwise condensers but has not yet achieved success.