Question

The heat transfer coefficient in film type condensation is _ _ _ _ that for drop wise condensation

• A. Greater than
• B. Lower than
• C. Is same as
• D. Twice

Hint:

Filmwise condensation gives lower heat transfer coefficient because the liquid film adds thermal resistance.

Answer 1

The Correct Option is B

Condensation may occur mainly in two forms: \[ \text{Filmwise condensation} \] and \[ \text{Dropwise condensation} \] In filmwise condensation, the condensate forms a continuous liquid film on the cooling surface. This liquid film acts as a resistance to heat transfer. Due to this extra resistance, heat transfer coefficient becomes lower. In dropwise condensation, the condensate forms small droplets on the surface. These droplets roll down and expose fresh surface for condensation. Hence, dropwise condensation gives much higher heat transfer coefficient than filmwise condensation. Therefore: \[ h_{\text{filmwise}} < h_{\text{dropwise}} \] So, the heat transfer coefficient in film type condensation is lower than that for dropwise condensation.