Heat Transfer problems
- 1. Increasing the liquor level in the evaporator results in the
Options- A. decreased capacity.
- B. increase in liquor film co-efficient.
- C. decreased effect of hydrostatic head.
- D. increased true temperature drop. Discuss
Correct Answer: decreased capacity.
- 2. The average heat transfer co-efficient for laminar film condensation on vertical surface is inversely proportional to (where, ?T = Temperature drop across condensate film )
Options- A. (?T)2
- B. ?T
- C. (?T)1/4
- D. (?T)3/2 Discuss
Correct Answer: (?T)1/4
- 3. In case of evaporators, liquid entrainment results primarily due to
Options- A. high vacuum in the evaporator.
- B. high evaporation rate.
- C. foaming of the solution.
- D. high heat transfer rate. Discuss
Correct Answer: foaming of the solution.
- 4. A backward feed multiple effect evaporator is better than forward feed for concentrating cold feed, because it provides
Options- A. higher economy
- B. lower capacity
- C. both (a) & (b)
- D. lower economy Discuss
Correct Answer: higher economy
- 5. Pick out the wrong statement.
Options- A. In case of heat transfer by purely forced convection, GR/Re2 ? 1.
- B. The equivalent diameter of heat transfer for a duct of square cross-section (having each side as 'x') is equal to 4x.
- C. Distillation process is not the same as evaporation.
- D. The effectiveness of nucleate boiling depends basically on the ease with which the bubbles are formed and detached from the heating surface. Discuss
Correct Answer: The equivalent diameter of heat transfer for a duct of square cross-section (having each side as 'x') is equal to 4x.
- 6. The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)R and the co-efficient of performance as a heat pump (COP)HP are
Options- A. (COP)R = (COP)HP = 0.6
- B. (COP)R = 2.5; (COP)HP = 1.5
- C. (COP)R = 1.5; (COP)HP = 2.5
- D. (COP)R = (COP)HP = 2.5 Discuss
Correct Answer: (COP)R = 1.5; (COP)HP = 2.5
- 7. Steam consumption in kg/hr in case of an evaporator is given by (where, C & E are capacity the economy of the evaporator respectively)
Options- A. C/E
- B. E/C
- C. CE
- D.
Discuss
Correct Answer: C/E
- 8. Thermal conductivity of a conducting solid material depends upon its
Options- A. temperature
- B. porosity
- C. both (a) & (b)
- D. neither (a) nor (b) Discuss
Correct Answer: both (a) & (b)
- 9. Economy of a multiple effect evaporator is not influenced much by the
Options- A. boiling point elevations
- B. temperature of the feed
- C. rate of heat transfer
- D. ratio of the weight of the thin liquor to thick liquor Discuss
Correct Answer: boiling point elevations
- 10. For shell and tube heat exchanger, with increasing heat transfer area, the purchased cost per unit heat transfer area
Options- A. increases
- B. decreases
- C. remains constant
- D. passes through a maxima Discuss
Correct Answer: passes through a maxima
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