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MCQs

Total Questions : 2525 | Page 3 of 253 pages
Question 21. Which of the following is not concerned with the heat transfer?
  1.    Brinkman number
  2.    Stanton number
  3.    Schmidt number
  4.    Peclet number
 Discuss Question
Answer: Option C. -> Schmidt number
Question 22. 1000 Kg of liquid at 30°C in a well stirred vessel has to be heated to 120°C, using immersed coils carrying condensing steam at 150°C. The area of the steam coils is 1.2 m² and the overall heat transfer co-efficient to the liquid is 1500 W/m².°C. Assuming negligible heat loss to the surrounding and specific heat capacity of the liquid to be 4 kJ/kg.°C, the time taken for the liquid to reach desired temperature will be
  1.    15 min
  2.    22 min
  3.    44 min
  4.    51 min
 Discuss Question
Answer: Option D. -> 51 min
Question 23. A cube, sphere & a thin circular plate (all having same mass and made of same material) are all heated to 300°C and allowed to cool in natural air. Which one will cool the slowest ?
  1.    Cube
  2.    Plate
  3.    Sphere
  4.    All of the above
 Discuss Question
Answer: Option C. -> Sphere
Question 24. Choose the correct equation.
  1.    Nu = (Re) (Pr) (Gz)
  2.    Nu = (Re) (Pr) (St)
  3.    Nu = (Re)(Pr)
  4.    Nu = (Pr)(St)
 Discuss Question
Answer: Option B. -> Nu = (Re) (Pr) (St)
Question 25. Fouling factor for a heat exchanger is given by (where, U₁ = heat transfer co-efficient of dirty surface U₂ = heat transfer co-efficient of clean surface)
  1.    U₁ - U₂
  2.    1/U₁ - 1/U₂
  3.    1/U₂ - 1/U₁
  4.    U₂ - U₁
 Discuss Question
Answer: Option B. -> 1/U₁ - 1/U₂
Question 26. A backward feed multiple effect evaporator is better than forward feed for concentrating cold feed, because it provides
  1.    Higher economy
  2.    Lower capacity
  3.    Both A & B
  4.    Lower economy
 Discuss Question
Answer: Option A. -> Higher economy
Question 27. Pick out the wrong statement.
  1.    In case of heat transfer by purely forced convection, GR/Re2 ? 1
  2.    The equivalent diameter of heat transfer for a duct of square cross-section (having each side as
  3.    Distillation process is not the same as evaporation
  4.    The effectiveness of nucleate boiling depends basically on the ease with which the bubbles are formed and detached from the heating surface
 Discuss Question
Answer: Option B. -> The equivalent diameter of heat transfer for a duct of square cross-section (having each side as
Question 28. Film boiling is usually not desired in commercial equipments, because
  1.    The heat transfer rate is low in view of the large temperature drop
  2.    It is difficult to maintain
  3.    It is not economic
  4.    None of these
 Discuss Question
Answer: Option A. -> The heat transfer rate is low in view of the large temperature drop
Question 29. Natural convection is characterised by
  1.    Grashhoff number
  2.    Peclet number
  3.    Reynolds number
  4.    Prandtl number
 Discuss Question
Answer: Option A. -> Grashhoff number
Question 30. Absorptivity and refletivity of a perfect black body are respectively
  1.    1 and 0
  2.    0 and 1
  3.    1 and ?
  4.    0 and 0.5
 Discuss Question
Answer: Option A. -> 1 and 0

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