chemical engineering heat transfer chemical engineering MCQs – Page 2

Practise multiple-choice questions from chemical engineering heat transfer chemical engineering for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

chemical engineering heat transfer chemical engineering Mcqs

21. In a co-current double pipe heat exchanger used for condensing saturated steam over the inner tube, if the entrance and exit conditions of the coolant are interchanged, then the rate of condensation will___________________?
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A. Either increase or decrease; depends on the coolant flow rate

B. Remain unchanged

C. Increase

D. Decrease

22. What is the emissivity of a black body ?
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A. 0.9

B. 0

C. 1

D. 0.5

23. Which area is used in case of heat flow by conduction through a cylinder ?
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A. Arithmetic mean area

B. Logarithmic mean area

C. Geometric mean area

D. None of these

24. Prandtl number is the reciprocal of____________________?
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A. Mass diffusivity Momentum diffusivity

B. Thermal diffusivity Mass diffusivity

C. Thermal diffusivity/Momentum diffusivity

D. Thermal diffusivity Momentum

25. Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the_________________?
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A. Existence of thermal boundary layer

B. Buoyancy of the bubbles produced at active nucleation site

C. Temperature gradient produced due to density difference

D. None of these

26. Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because___________________?
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A. Conduction becomes important

B. Sub-cooled boiling occurs

C. Radiation becomes important

D. Convection becomes important

27. Overall heat transfer co-efficient of a particular tube is U1. If the same tube with some dirt deposited on either side has coefficient U2, then_________________?
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A. U2 > U1

B. U1 > U2

C. U1 = U2

D. U1 = dirt factor U2

28. For large heat transfer area requirement, shell and tube heat exchanger is preferred, because it________________?
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A. All A., B. and C.

B. Occupies smaller space

C. Is more economical

D. Is easy to operate and maintain

29. In a forward feed multiple effect evaporator, the pressure is ____________________?
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A. Dependent on the number of effects

B. Same in all effects

C. Lowest in last effect

D. Highest in last effect

30. Presence of a non-condensing gas in a condensing vapour___________________?
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A. Increases the rate of condensation

B. Decreases thermal resistance

C. None of these

D. Is desirable to increase the film co-efficient

31. Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids are clean and non-fouling ?
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A. Square pitch

B. Triangular pitch

C. None of these

D. Diagonal square pitch

32. Which of the following parameters is increased by use of finned tube in a multipass shell and tube heat exchanger ?
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A. Convective heat transfer co-efficient

B. Effective tube surface area for convective heat transfer

C. All A. B. and C.

D. Tube side pressure drop and the heat transfer rate

33. Tube pitch is the _______________ of tube diameters and the clearances?
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A. Sum

B. None of these

C. Difference

D. Ratio

34. The capacity of double-effect evaporator is less than half of the capacity of two single effects, each of which is operating over same terminal temperature difference, when the________________ ?
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A. None of these

B. Evaporators operate at atmospheric pressure

C. Solution has an elevation of boiling point

D. Evaporators operate under vacuum

35. Which has the lowest Prandtl number ?
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A. Water

B. Aqueous solution

C. Liquid metal

D. Lube oil

36. Thermal conductivity of a gas at low density, ___________ with increase in temperature ?
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A. May increase or decrease; depends on the gas

B. Remains unchanged

C. Increases

D. Decreases

37. Which one gives the monochromatic emissive power for black body radiation ?
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A. Plancks law

B. Kirchhoffs law

C. Wiens law

D. Stefan-Boltzmann law

38. The absorptivity of a grey body at a given temperature _____________ with increasing wavelength of radiation?
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A. May increase or decrease; depends on the material

B. Remain constant

C. Decreases

D. Increases

39. What is the geometric mean of two heat transfer areas A1 and A2 ?
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A. ?(A1 . A2)

B. ?(A1 + A2)

C. ?(A1 . A2)

D. 2 ?(A1 . A2)

40. Heat sensitive materials can be concentrated in an evaporator employing_______________?
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A. High pressure

B. Vacuum

C. High residence time

D. None of these

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