51. In a multiple effect evaporator, the effect of boiling point elevation is to
Reduce the capacity
Reduce the economy
Increase the economy
None of these
✅ The correct answer is option A.
Heat Transfer MCQs
52. The unit of heat transfer co-efficient is
BTU/hr. ft²°F
BTU/hr. °F. ft
BTU/hr. °F
BTU/hr. ft
✅ The correct answer is option A.
53. Steam is to be condensed in a shell and tube heat exchanger, 5 m long with a shell diameter of 1 m. Cooling water is to be used for removing the heat. Heat transfer co-efficient for the cooling water, whether on shell side or tube side is the same. The best arrangement is
Vertical heat exchanger with steam on tube side
Vertical heat exchanger with steam on shell side
Horizontal heat exchanger with steam on tube side
Horizontal heat exchanger with steam on shell side
✅ The correct answer is option B.
54. The average heat transfer co-efficient for laminar film condensation on vertical surface is inversely proportional to (where, ΔT = Temperature drop across condensate film )
(ΔT)2
√ΔT
(ΔT)1/4
(ΔT)3/2
✅ The correct answer is option C.
55. If average heat transfer co-efficient is ha and the local coefficient at the end of the plate is hl then in case of heat transfer to a fluid flowing over a flat plate, heated over its entire length
Ha = hl
Ha = 2hl
Ha = 0.5 hl
Ha = 0.75 hl
✅ The correct answer is option B.
56. Stefan-Boltzman law which describes the radiation heat transfer states that, it is proportional to (where, t = temperature in °C T = absolute temperature in ° K )
t⁴
T⁴
1/t⁴
1/T⁴
✅ The correct answer is option B.
57. The main function of baffles provided in a shell and tube heat exchanger is to
Facilitate the cleaning of outer tube surface
Enhance turbulence
Hold the tubes in position
All of the above
✅ The correct answer is option B.
58. Overall heat transfer co-efficient of a particular tube is U₁. If the same tube with some dirt deposited on either side has coefficient U₂, then
U₁ = U₂
U₂ > U₁
U₁ > U₂
U₁ = dirt factor – U₂
✅ The correct answer is option A.
59. What is the thermal conductivity of a perfect heat insulator?
Zero
One
∞
Between 0 and ∞
✅ The correct answer is option A.
60. Which of the following is correct?
Rate = Driving force x Resistance
Driving force = Rate x Resistance
Resistance = Driving force x Rate
Rate = Resistance/Driving force
✅ The correct answer is option B.