# Chemical Engineering - Heat Transfer

### Exercise :: Heat Transfer - Section 1

46.

The average heat transfer co-efficient for laminar film condensation on vertical surface is inversely proportional to (where, ΔT = Temperature drop across condensate film )

 A. (ΔT)2 B. ΔT C. (ΔT)1/4 D. (ΔT)3/2

Explanation:

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47.

Bulk of the convective heat transfer resistance from a hot tube surface to the fluid flowing in it, is

 A. in the central core of the fluid. B. uniformly distributed throughout the fluid. C. mainly confined to a thin film of fluid near the surface. D. none of these.

Explanation:

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48.

Which of the following is concerned with both heat and mass transfer ?

 A. Lewis relationship B. Nusselt number C. Kutateladze number D. Froude number

Explanation:

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49.

A backward feed multiple effect evaporator is better than forward feed for concentrating cold feed, because it provides

 A. higher economy B. lower capacity C. both (a) & (b) D. lower economy

Explanation:

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50.

A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m2.°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be

 A. greater than that for uninsulated steam pipe. B. less than that of the uninsulated steam pipe. C. equal to that of the uninsulated steam pipe. D. less than the steam pipe with 5 cms insulation.