Difference Between Drop wise and Film Wise Condensation

Drop-wise Condensation :

1.When a saturated vapour comes into contact with a cold surface (a surface at a lower temperature), it condenses and if condensate does not wet the surface, the droplets formed on the surface. These droplets grow and ultimately fall down the surface in a random fashion under the influence of gravity leaving behind the bare metal surface on which further condensation takes place. The condensation occurring by this mechanism is known as drop- wise condensation.

2.Heat transfer coefficients are very high as the heat does not have to flow through a film by conduction.

                                            

                            

3.Oily or greasy surfaces seem to tend towards drop-wise condensation.
4.Drop-wise condensation is very difficult to achieve.
5.Drop-wise condensation is unstable and difficult to maintain, uncommon and so not desired industrially.
6.Heat transfer coefficients and heat transfer rates are very high.

Film-wise Condensation :

1.When a saturated vapour comes into contact with a cold surface, it condenses and if condensate wets the surface, it forms a continuous film of condensate, which covers the entire surface, through which heat must be transferred. The additional vapour is then required to condense into the liquid film rather than directly on the surface. The condensate ultimately flows down the surface under the influence of gravity. The condensation occurring by this mechanism is called as film wise condensation.
                                    

                                            

                        

                                  

2.Heat transfer coefficients are relatively very since heat doesn't have to  flow through a film by conduction.

3.Film-wise condensation is easily obtainable.
4.Film-wise condensation is stable, easy, reliable, very common
5.Heat transfer coefficients and heat transfer rate are low.