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Depth of liquid over heating surface
Pressure difference between steam chest and vapour space
All of the above
✅ The correct answer is option D.
Heat Transfer MCQs
182. The overall resistance for heat transfer through a series of flat resistance, is the __________ of the resistances.
Average
Geometric mean
Product
Sum
✅ The correct answer is option D.
183. Boiling of milk in an open vessel is an example of __________ boiling.
Film
Sub-cooled
Saturated nucleate
None of these
✅ The correct answer is option A.
184. A steel sphere of radius 0.1 m at 400°K is immersed in an oil at 300°K. If the centre of the sphere reaches 350°K in 20 minutes, how long will it take for a 0.05 m radius steel sphere to reach the same temperature (at the centre) under identical conditions ? Assume that the conductive heat transfer co-efficient is infinitely large.
5 minutes
10 minutes
20 minutes
40 minutes
✅ The correct answer is option A.
185. In sub-cooled boiling,
Temperature of the heating surface is less than the boiling point of the liquid
Temperature of the heating surface is more than the boiling point of the liquid
Bubbles from heating surface are absorbed by the mass of the liquid
Very large vapour space is necessary
✅ The correct answer is option B.
186. In a cooling tower, water becomes cool by
Loosing sensible heat
Heat transfer to surroundings
Vaporisation due to heat loss to air
Loosing latent heat
✅ The correct answer is option A.
187. Duhring rule is important in solving problems on
Distillation
Crystallisation
Evaporation
Humidification
✅ The correct answer is option C.
188. Corrosiveness of steam condensate is due to the presence of
CO₂
Dissolved O₂
Both A & B
Neither A nor B
✅ The correct answer is option C.
189. __________ heat exchanger is used for chilling oil to be dewaxed.
U-tube
Double pipe
Fixed tube
Floating head
✅ The correct answer is option B.
190. The average heat transfer co-efficient over the entire length of the plate (ha) and the local heat transfer co-efficient (hL), in case of heat transfer over a flat plate in lminar zone is related as
Ha = 0.8hL
Ha = 2hL
Ha = hL
Ha= 5hL
✅ The correct answer is option B.