Heat Transfer

371. The local surface conductance for laminar film condensation on vertical surface is (where, t = film thickness)

1. ∝ t
2. ∝ 1/t
3. ∝ √t
4. Independent of 't'

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372. The main function of baffles provided in a shell and tube heat exchanger is to

1. Facilitate the cleaning of outer tube surface
2. Enhance turbulence
3. Hold the tubes in position
4. All 'a', 'b' & 'c'

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373. The main purpose of providing fins on heat transfer surface is to increase the

1. Temperature gradient
2. Mechanical strength of the equipment
3. Heat transfer area
4. Heat transfer co-efficient

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374. The maximum heat transfer co-efficient from steam heating will be attained when the steam is:

1. Supersaturated
2. Saturated
3. Wet
4. None of these

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375. The most conducive surface for dropwise condensation to occur is the _________ surface.

1. Coated
2. Oily
3. Glazed & polished
4. Smooth

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376. The non-dimensional temperature gradient in a liquid at the wall of a pipe is the

1. Heat flux
2. Nusselt number
3. Prandtl number
4. Schmidt number

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377. The number of kg vaporised per kg of steam fed to the evaporator is defined as

1. Capacity
2. Rate of evaporation
3. Economy
4. Rate of vaporisation

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378. The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is

1. 1.66
2. 88.66
3. 3.66
4. Dependent on N_Re only

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379. The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe, where the wall heat flux is constant, is

1. 2.36
2. 4.36
3. 120.36
4. Dependent on NRe only

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