E-PolyLearning

31. With the increase of temperature, the Col-burn jH factor
a. increases.
b. decreases.
c. remains unchanged.
d. may increase or decrease ; depending on temperature.
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Answer: (a).increases.

32. In case of evaporators, liquid entrainment results primarily due to
a. high vacuum in the evaporator.
b. high evaporation rate.
c. foaming of the solution.
d. high heat transfer rate.
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Answer: (c).foaming of the solution.

33. Baffles in the shell side of a shell and tube heat exchanger
a. increase the cross-section of the shell side liquid.
b. force the liquid to flow parallel to the bank.
c. increase the shell side heat transfer co-efficient.
d. decrease the shell side heat transfer co-efficient.
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Answer: (c).increase the shell side heat transfer co-efficient.

34. Air is to be heated by condensing steam. Two heat exchangers are available (i) a shell and tube heat exchanger and (ii) a finned tube heat exchanger. Tube side heat transfer area are equal in both the cases. The recommended arrangement is
a. finned tube heat exchanger with air inside and steam outside.
b. finned tube heat exchanger with air outside and steam inside.
c. shell and tube heat exchanger with air inside tubes and steam on shell side.
d. shell and tube heat exchanger with air on shell side and steam inside tubes.
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Answer: (b).finned tube heat exchanger with air outside and steam inside.

35. The unit of heat transfer co-efficient in SI unit is
a. J/m²°K
b. W/m²°K
c. W/m°K
d. J/m°K
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Answer: (b).W/m²°K