Nusselt number in Boiling and Condensation process is prescribed by the function
For condensation or boiling, the convection coefficient depends upon ΔT = (Tw- Tsat), the body force arising from the liquid-vapour density difference, g ( ρi - pv) , the latent heat hfg, the surface tension σ, a characteristic length L and the thermophysical properties of the liquid or vapour p, cp, μ, and K. From dimensionless analysis,
Which of the above statements are valid?
All of the following assumptions for Nusselt’s theory of laminar film condensation on a vertical plate is correct except
Consider boiling curve for pool boiling of water at saturation temperature and atmospheric pressure and match the following
III Transition boiling
IV Film boiling Point
P→ Maximum / Critical heat flux or Burnout point
Point Q → Minimum heat flux (Leidenfrost point) Point Pis also known as boiling crisis indicating the onset of departure from nucleate boiling.
The convective coefficients for boiling and condensation usually lie in the range (W/m2-K)
Dropwise condensation usually occurs on
Consider the following statements:
1. If a condensing liquid does not wet a surface, then dropwise condensation will not take place un it:
2. Dropwise condensation gives a higher transfer rate than filmwise condensation.
3. Reynolds number of condensing liquid is based on its mass flow.
4. Suitable coating or vapour additive is used to promote filmwise condensation.
Which of these statements are correct?
5 In condensation over a vertical surface, the value of convection coefficient varies as
Where k is the thermal conductivity of the liquid
The average heat transfer coefficient is given by
Which of the followings is a wrong statement in the context of convective heat transfer coefficient in laminar film condensation?The heat transfer coefficient varies as
From this equation:
For filmwise condensation on a vertical plane; the film thickness 5 and heat transfer coefficient h vary with distance* from the leading edge as