E-PolyLearning

21. Prandtl number is given by
a. A
b. B
c. C
d. D
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Answer: (c).C

22. For a liquid in laminar flow through a very long tube, when the exit fluid temperature approaches the wall temperature, the equation to be used is
a. A
b. B
c. C
d. D
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Answer: (c).C

23. A graph between __________ is called Wilson plot.
a. A
b. B
c. C
d. D
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Answer: (a).A

24. What is the geometric mean of two heat transfer areas A1 and A2 ?
a. A
b. B
c. C
d. D
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Answer: (a).A

25. Hot water (0.01 m³ /min) enters the tube side of a counter current shell and tube heat exchanger at 80°C and leaves at 50°C. Cold oil (0.05 m³/min) of density 800 kg/m³ and specific heat of 2 kJ/kg.K enters at 20°C. The log mean temperature difference in °C is approximately
a. 32
b. 37
c. 45
d. 50
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Answer: (a).32

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