chemical engineering MCQs – Page 191

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 Review each marked answer and report any item that may be outdated or unclear.

chemical engineering Mcqs

3801. For the same heat load and mass flow rate in the tube side of a shell and tube heat exchanger, one may use multipass on the tube side, because it__________________?
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A. Decreases the outlet temperature of cooling medium

B. Decreases the pressure drop

C. Increases the overall heat transfer coefficient

D. None of these

3802. 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. Radiation becomes important

B. Sub-cooled boiling occurs

C. Conduction becomes important

D. Convection becomes important

3803. The ratio of lateral strain to linear strain is termed as the___________________?
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A. Poissons ratio

B. Bulk modulus

C. Shear modulus

D. Modulus of elasticity

3804. Liquid gradient over a tray can be minimised by________________?
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A. Providing a higher skirt clearance or a higher weir

B. Decreasing the number of rows of caps through which the liquid flows or by decreasing the

C. All A., B. and C.

D. Using split flow, radial flow or cascade flow for column diameter large than 4 ft

E. ocity of liquid flow past the caps or by reducing the distance along the tray through which

F. liquid must flow

3805. Indirect contact heat exchangers are preferred over direct contact heat exchangers, because_________________?
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A. There is no mist formation

B. Cost of equipment is lower

C. Heat transfer co-efficient are high

D. There is no risk of contamination

3806. In a shell and tube heat exchanger, putting a longitudinal baffle across the shell, forces the shell side fluid to pass _____________ through the heat exchanger ?
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A. Twice

B. Thrice

C. Four times

D. Once

3807. Nusselt number is a function of Prandtl number and ______________ number of fluid in natural convection heat transfer?
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A. Reynolds

B. Biot

C. Grashoff

D. Stanton

3808. In case of heat flow by conduction for a cylindrical body with an internal heat source, the nature of temperature distribution is_________________?
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A. Hyperbolic

B. Parabolic

C. Linear

D. None of these

3809. At constant temperature, the thermal conductivities of gases _____________ with rise in pressure?
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A. Remain unchanged

B. Decrease

C. Increase

D. May increase or decrease; depends on the pressure

3810. Extremely large or small volumes of fluids are generally best routed through the shell side of a shell and tube heat exchanger, because of the________________?
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A. Flexibility possible in the baffle arrangement

B. High heat transfer co-efficient

C. Low pressure drop

D. Less corrosion problems

3811. (Le/D) for a Tee (used as elbow, entering branch) would be ____________________?
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A. Less than that for Tee (used as elbow, entering run)

B. More than that for Tee (used as elbow, entering run)

C. Around 90

D. Both B. and C.

3812. With increase in temperature, the total emissivity of conductors____________________?
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A. Remain same

B. Decreases

C. Decreases linearly

D. Increases

3813. Forced circulation evaporators are normally used for concentrating liquids having ___________________?
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A. Scaling characteristics

B. High viscosity

C. Both A. & B.

D. Neither A. nor B.

3814. The absorptivity of a grey body at a given temperature _____________ with increasing wavelength of radiation?
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A. Remain constant

B. Increases

C. May increase or decrease; depends on the material

D. Decreases

3815. Electro-magnetic spectrum range, which is important for radiation varies from _____________ microns?
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A. 10 to 100

B. 100 to 1000

C. 0.5 to 50

D. 1 to 100

3816. LMTD for counter-flow and parallel flow heat exchanger will be the same, when the_________________?
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A. Cold fluid is heated to a certain temperature by condensing steam (isothermal fluid)

B. Outlet temperature of both the hot and cold fluid are same

C. Outlet temperature of hot fluid is less than the outlet temperature of the cold fluid

D. None of these

3817. It is not recommended to use a 1-2 shell and tube heat exchanger for a particular heat duty, whenever the LMTD correction factor is___________________?
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A. > 0.75

B. < 0.75

C. < 0.50

D. < 0.25

3818. The average velocity in the tubes of a 1-4 heat exchanger is ______________ times that in 1-1 heat exchanger having the same size & number of tubes and operated at same liquid flow rate ?
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A. 4

B. 2

C. 4-Jan

D. 2-Jan

3819. In a multiple effect evaporator system having n effects, the amount of water evaporated per unit surface area in approximately equal to _____________ times that in a single effect?
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A. 0.5 nth

B. nth

C. (1/n)th

D. 1.5 nth

3820. The centre to centre distance between two consecutive baffles in a shell and tube heat exchanger is called the baffle pitch or baffle spacing, which is more than 1/5th the I.D. of the shell. Which of the following is not a function of the baffles ?
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A. To increase the tube side heat transfer co-efficient by inducing turbulence

B. To reduce the induced vibration in the tubes

C. To increase the residence time of shell side fluid

D. To provide support to the tube bundle

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