1)      Condensation occurs when the temperature of a vapor is reduced below its saturation temperature

a)      It can occur at solid surface as well as free surface of liquid or the gas.

b)      Two distinct forms of condensation are observed:

i)        Film condensation: The condensate wets the surface and forms a liquid film on the surface that slides down under the influence of gravity. The thickness of the liquid film increases in the flow direction as more vapors condense on the film. This is how condensation normally occurs in practice.

ii)      Dropwise condensation : he condensed vapor forms droplets on the surface instead of a continuous film, and the surface is covered by countless droplets of varying diameters