31 - Condensation

Dropwise condensation is superior to filmwise condensation. In dropwise condensation most of the heat transfer is through drops of diameters of less than 100-\(\mu\)m and heat transfer rates are more than an order of magnitude larger than those with filmwise condensation.

To promote dropwise condensation, it is common practice to use surface coatings to inhibit wetting. Slicones, Teflon, waxes and fatty acids are often used for this purpose. However, such coatings gradually lose their effectiveness due to oxidation, fouling, or erosion, and filmwise condensation eventually occurs. For this reason, condenser design calculations are often based on the assumption of filmwise condensation.