E-PolyLearning

51. In case of vertical tube evaporator, with increase in liquor level, the overall heat transfer co-efficient
a. increases
b. decreases
c. is not affected
d. may increase or decrease; depends on the feed
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Answer: (b).decreases

52. The steam ejector is used to
a. remove condensate from the steam pipelines.
b. create vacuum.
c. superheat the steam.
d. none of these.
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Answer: (b).create vacuum.

53. For shell and tube heat exchanger, with increasing heat transfer area, the purchased cost per unit heat transfer area
a. increases
b. decreases
c. remains constant
d. passes through a maxima
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Answer: (d).passes through a maxima

54. 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
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
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Answer: (c).(COP)R = 1.5; (COP)HP = 2.5

55. Crystal size in a continuous crystalliser depends upon the
a. rate of heat transfer.
b. degree of turbulence.
c. degree of supersaturation.
d. all (a), (b) and (c).
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Answer: (d).all (a), (b) and (c).