Computerized Condensation in Drop wise & Film wise

Description

Condensation is the change in phase from the vapor state to the liquid or solid state. It can be considered as taking place either within a bulk material or on a cooled surface and is accompanied by simultaneous heat and mass transfer. Condensation plays a significant role in the heat rejection parts of the Rankine power cycle and the vapor compression refrigeration cycle, which generally involve pure substances. Dehumidification in air conditioning and the production of liquefied petroleum gases, liquid nitrogen and liquid oxygen and examples in which condensation in a mixture takes place. Condensation on cooled surface occurs in one of two ways: Film or Drop wise condensation.

In film condensation the liquid condensation forms a continuous film which covers the surface and takes place when the liquid wets the surface. This film flows over the surface under the action of gravity or other body surface, surface tension and shear stresses due to vapor flow. Heat transfer to the solid surface takes place through the film which forms the greatest part of the thermal resistance.

In Drop wise condensation the vapor impinges on the cool wall, reducing its energy and thereby liquidizing and forming drops which grow by direct condensation of vapor on the drops and by coalescence with neighboring drops until the drops are swept off the surface by the action of gravity or other body forces, surface tension and shear stresses due to Vapour flow. As the drops move they coalesce with other droplets in their path, sweeping a portion of the surface clean so that condensation can begin. The details of drop wise condensation are not completely understood but it is known to take place under circumstance where the liquid does not wet the surface.