chemical engineering MCQs – Page 188

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 Review each marked answer and report any item that may be outdated or unclear.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

3741. Pick out the wrong statement about the design of sieve plate column and the bubble cap column ?
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A. Weir height for a bubble cap plate column is the same as that for a sieve plate column

B. ve plate

C. te and bubble cap columns

D. The downcomer design and the residence time in the downcomer is almost same for sieve

E. Weir height in case of a bubble cap plate ranges from 50 to 150 mm and is higher than the

F. Weir length for a bubble cap plate is the same as that for the sieve plate

3742. In a multipass shell and tube heat exchanger, the shell side cross flow area does not depend upon______________________?
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A. Clearance

B. None of these

C. Pitch

D. Baffle spacing

3743. Which of the following is the most common type of baffle used in industrial shell and tube heat exchanger ?
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A. 25% cut segmental baffle

B. Disk and doughnut baffle

C. Orifice baffle

D. 75% cut segmental baffle

3744. To keep the power input constant for a stirred vessel operating under fully developed turbulent flow conditions (constant power number), if the impeller diameter is increased by 20%, the impeller speed should be decreased by a factor of_________________?
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A. (1.2)3/5

B. (1.2)5/3

C. (1.2)3/2

D. (1.2)2/3

3745. Fresh water carrying pipelines in chemical industries are coloured with _______________ color?
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A. Red

B. Brown

C. Sea green

D. Yellow

3746. Which of the following factors determine the amount of entrainment in a distillation column ?
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A. Plate spacing

B. Depth of liquid above the bubble cap slots

C. All A., B. and C.

D. Vapour velocity in the volume between the plates

3747. The clearance between two tubes in a shell and tube heat exchanger is known as ligament, whose minimum value is _____________ the outside diameter of the tube, but in no case it should be less than 4.5 mm?
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A. Half

B. Equal to

C. One fourth

D. Three fourth

3748. In the design of a shell and tube heat exchanger, the corrosion allowance ____________________?
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A. Need not be provided for non-pressure parts like tie rods, spacers, baffles, supports etc.

B. For carbon steel and cast iron pressure parts is 1.5 mm (except for tubes) and for severe

C. ditions it is 3 mm

D. For internal cover and tube sheet is provided on both the sides

E. All A., B. & C.

3749. Pick out the wrong statement pertaining to the comparative evaluation of performance of the packed tower and the plate tower ?
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A. In operations involving large temperature changes. (e.g. distillation), plate towers are

B. ferred over packed towers as the packing may be crushed due to large temperature changes

C. ution

D. Plate tower is preferred over packed tower, if the operation involves liquids containing

E. Plate tower is preferred, if interstage cooling is required to remove heats of reaction or

F. The total weight of a dry plate tower is usually much more than that of a dry packed tower

3750. A perforated plate has holes of diameter dn arranged in a pitch ph. Each hole has a tube of I.D. dt passing through it. The ligament efficiency is given by_______________?
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A. (ph dh . dt/2)/ph

B. (ph dt)/ph

C. (ph dh)/ph

D. (ph dh)/dh

3751. Column support for the roof of cylindrical storage tank must be provided for___________________?
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A. All tanks irrespective of their heights and diameters

B. Large diameter tanks

C. Small diameter tall tanks

D. Small diameter tanks

3752. Baffle spacing is generally _________________ the I.D. of the shell ?
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A. More than

B. Not greater than

C. Not less than one fifth of

D. Both B. and C.

3753. Tubes are fixed to the tube sheet (a thick circular metallic plate) by the method of tube rolling and brazing (non-removable) or ferrule connection (removable). Thickness of the tube, sheet is normally ____________ the outside diameter of the tube but in no case it should be less than 22 mm (7/8?)?
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A. Three fourth

B. Equal to

C. Half

D. 1.5 times

3754. In Biot number, the characteristic length used is the ratio of the _______________ of the solid?
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A. Surface area to volume

B. Surface area to perimeter

C. Volume to surface area

D. Perimeter to surface area

3755. Ratio of tube length to shell diameter for a shell and tube heat exchanger is________________?
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A. 8 : 1 to 12 : 1 for both liquid-liquid and gas-gas heat exchangers

B. 4 : 1 to 8 : 1 for liquid-liquid exchanger

C. < 4 : 1 for gas-gas exchangers

D. Both B. & C.

3756. 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______________?
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A. Nu = 0.023 Re0.8. Pr0.4

B. Nu = 2Gz0.5

C. Nu = (2/?) Gz

D. Nu = (?/2) Gz

3757. In a shell and tube heat exchanger for a given heat transfer surface area, smaller diameter tubes are favoured as compared to larger diameter ones; because the smaller diameter tubes ______________?
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A. None of these

B. Are less prone to fouling

C. Are easier to clean

D. Can be fitted into a smaller shell diameter hence the cost of the heat exchanger would be less

3758. The distance between the centres of a rivet hole to the nearest edge of the plate is called _________________?
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A. Pitch

B. None of these

C. Margin

D. Back pitch

3759. Safety valves are provided in chemical equipments to guard against excessive_________________?
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A. Noise

B. Pressure/pressure fluctuation

C. Turbulence

D. Temperature

3760. Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100C and the inside heat transfer coefficient is 3k/l. If the wall temperature on the outside is held at 25C, what is the inside wall temperature in degree centigrade ?
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A. 48.25

B. 35.5

C. 43.75

D. 81.25

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