Dropwise condensation occurs on __________ surfaces.

ANS:C - contaminated cooling

When we talk about dropwise condensation, it's helpful to understand the distinction between dropwise and filmwise condensation.

1. Dropwise Condensation: This occurs when individual droplets form on the condensing surface and then detach from it due to gravity. The surface remains relatively dry as these droplets fall off, which promotes further condensation. Dropwise condensation is generally more efficient in heat transfer compared to filmwise condensation because the droplets provide fresh surface areas for condensation to occur. It typically occurs on clean, smooth surfaces where the droplets can easily form and detach.
2. Filmwise Condensation: In contrast, filmwise condensation happens when a continuous film of condensed liquid covers the condensing surface. This film can hinder further condensation by acting as an insulating layer, reducing the heat transfer efficiency. Filmwise condensation is more likely to occur on rough or contaminated surfaces where droplets have difficulty forming and detaching.