351. Dropwise condensation is promoted on a/an __________ surface.
Glazed
Oily
Coated
Smooth
✅ The correct answer is option B.
Heat Transfer MCQs
352. In a shell and tube heat exchanger, putting a longitudinal baffle across the shell, forces the shell side fluid to pass __________ through the heat exchanger.
Once
Twice
Thrice
Four times
✅ The correct answer is option B.
353. Which area is used in case of heat flow by conduction through a cylinder?
Logarithmic mean area
Arithmetic mean area
Geometric mean area
None of these
✅ The correct answer is option A.
354. Sensible heat of hot industrial flue gases can not be recovered by a/an
Economiser
Regenerator
Ceramic recuperator
None of these
✅ The correct answer is option D.
355. A tank painted with which of the following coloured paints, would heat up maximum by radiation from sun?
Yellow paint
White paint
Black paint
Grey paint
✅ The correct answer is option C.
356. Steam traps are provided in steam carrying pipelines to
Condense steam
Release excess steam pressure by bleeding steam
Remove condensate and inert gases
None of these
✅ The correct answer is option C.
357. The critical radius ‘r’ of insulation on a pipe is given by
r = 2k/h
r = k/h
r = k/2h
r = h/k
✅ The correct answer is option B.
358. Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100°C and the inside heat transfer co-efficient is 3k/l. If the wall temperature on the outside is held at 25°C, what is the inside wall temperature in degree centigrade?
35.5
43.75
81.25
48.25
✅ The correct answer is option C.
359. In thermal radiation for a black body (where, ε is emissivity and α is absorptivity)
α = 1; ε ≠ 1
α ≠ 1, ε = 1
α ≠ 1, ε ≠ 1
α = 1; ε = 1
✅ The correct answer is option D.
360. The film co-efficient is decreased due to the presence of non-condensing gases in the vapors. The film co-efficient of superheated vapor as compared to that of saturated vapor is
More
Less
Some
Either more or less ; depends on the nature of vapor
✅ The correct answer is option C.