E-PolyLearning

36. The number of kg vaporised per kg of steam fed to the evaporator is defined as
a. capacity
b. rate of evaporation
c. economy
d. rate of vaporisation
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Answer: (c).economy

37. Pick out the wrong statement.
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.
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Answer: (b).The equivalent diameter of heat transfer for a duct of square cross-section (having each side as 'x') is equal to 4x.

38. Economy of a multiple effect evaporator is not influenced much by the
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
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Answer: (a).boiling point elevations

39. Increasing the liquor level in the evaporator results in the
a. decreased capacity.
b. increase in liquor film co-efficient.
c. decreased effect of hydrostatic head.
d. increased true temperature drop.
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Answer: (a).decreased capacity.

40. Pick out the wrong statement.
a. Orifice baffles are never used in a shell and tube heat exchanger.
b. Pressure drop on the shell side of a heat exchanger depends upon tube pitch also.
c. In a horizontal tube evaporator, surface blanketing by air is avoided.
d. Split ring type and pull through type floating heads are two commonly used floating heads is heat exchangers.
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Answer: (a).Orifice baffles are never used in a shell and tube heat exchanger.