Consider the following statements :
1. If a condensing liquid does not wet a surface dropwise, then condensation will take place on it.
2. Dropwise condensation gives a higher heat transfer rate than filmwise condensation
3. Reynold number of condensing liquid is based on its mass flow rate.
4. Suitable coating or vapour additive is used to promote filmwise condensation.
Of these statements
Option (A)
1 and 2 are correct
Option (B)
2,3 and 4 are correct
4 alone is correct
1, 2 and 3 are correct
Correct Option:
Question Solution:
Heat transfer across the film is due to pure conduction and temperature difference in linear.
In dropwise condensation, the heat transfer coefficient is higher than in film wise condensation. So some additive condensation promoter (oleic acid)and polished surface promotes dropwise condensation
The flow of condensate in the film is laminar Renold number m = (4m/Cb) = 4r1umÎ /l)