E-PolyLearning

11. Thermal diffusivity is given by
a. A
b. B
c. C
d. D
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Answer: (a).A

12. At steady state the temperature variation in a plane wall, made of two different solids I & II is shown below. The thermal conductivity of material I
a. is smaller than that of II.
b. is greater than that of II.
c. is equal to that of II.
d. can be greater than or smaller than that of II.
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Answer: (a).is smaller than that of II.

13. In case of surface condensers, a straight line is obtained on plotting 1/U vs __________ on an ordinary graph paper.
a. A
b. B
c. C
d. D
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Answer: (a).A

14. 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)
a. A
b. B
c. C
d. D
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Answer: (b).B

15. For a counter current heat exchanger with Tih = 80°C, T°c = 60°C, T°h = 50°C and Tic = 30°C, and the temperature difference between the two streams being the same everywhere along Z, the direction of flow of hot fluid. The temperature profile should satisfy
a. A
b. B
c. C
d. D
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Answer: (b).B

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