Chemical Engineering - Heat Transfer - Discussion

Condensation is the change of phase from the vapour state to the liquid or solid-state By conduction and convection reduces the heat transfer rate considerably compared with dropwise condensation. This is the reason that the heat transfer rate of filmwise condensation is lower than dropwise condensation.

N film condensation, a growing film covers the surface, creating a thermal resistance that reduces heat transfer.

In dropwise condensation, much of the surface is exposed directly to vapour, allowing heat-transfer rates up to ten times higher than in film condensation.

When a film is formed in filmwise condensation than that film of liquid provides additional resistance to heat flow. So, due to that additional resistance, the heat transfer coefficient reduces.