Heat Transfer: Theory and Problems

7

Condensation

If vapour comes in contact with a surface maintained at a temperature below the saturation temperature of the vapour, then condensation occurs. The liquid condensate will flow down on the surface under the influence of gravity. When the liquid wets the surface, spreads out and forms a film, this process is known as filmwise condensation. If the surface is not wetted by the liquid, then droplets form and run down the surface. This process is known as dropwise condensation. Heat transfer rate in dropwise condensation is nearly 10 times higher than in the filmwise condensation process. But dropwise condensation is very difficult to achieve in practical cases. All practical design methods are based on filmwise condensation. The heat ...