chemical engineering Mcqs
3701. In a heat exchanger, shell side fluid velocity can be changed by changing the tube _______________________?
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A. Layout

B. Pitch

C. Both A. & B.

D. Neither A. nor B.

3702. Liquid gradient over the tray results due to the___________________?
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A. Large plate spacing

B. Resistance offered to flow of liquids by caps & risers and the flow of gas

C. Large reflux ratio

D. Low gas velocity

3703. 1.2 to 3.8 cms is the value of the ______________________?
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A. Skirt clearance for bubble caps

B. All A., B. and C.

C. Static submergence in case of a bubble cap tray for column operating under pressure (? 1 atm)

D. Downcomer liquid seal in case of a balanced tray design

3704. Generally, as the length of the liquid path on a tray is increased beyond 5 ft, the overall column efficiency___________________?
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A. May increase or decrease depending upon the plate spacing

B. Remain same

C. Increases

D. Decreases

3705. A high vapour velocity is required for high plate efficiency in a sieve plate column. The satisfactory value of operating vapor velocity for design purpose in sieve plate column is about _______________ percent of the flooding velocity?
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A. 45

B. 95

C. 60

D. 80
3706. Pick out the wrong statement pertaining to the design of a long tube vertical evaporator ?
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A. Steam is fed to the shell, whereas the liquor is filled inside the tube

B. Tube dia is 3-6 cms, while tube length in 3-6 metres

C. None of these

D. Liquor level is maintained at 1/3rd to 1/2 of the height of the tube

3707. A binary liquid Azeotropic mixture has boiling point higher than either of the components, when it shows ______________ deviation from Raoults Law?
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A. No

B. Positive

C. Negative

D. None of these

3708. A rupture disc is provided in chemical equipments as an accessory meant for ___________________?
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A. Creating turbulence

B. Avoiding vortex formation

C. Enhancing mixing rate

D. Relieving excess pressure
3709. In the case of a shell and tube heat exchanger, the logarithmic mean temperature difference ______________________?
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A. Is always more than arithmetic mean value and the geometric mean value

B. ther the flow of stream is co-current or counter-current

C. Is always less than arithmetic average value

D. May be either more or less than geometric mean and arithmetic mean value depending upon

E. Is always less than arithmetic mean value, but more than geometric mean value

3710. In sieve plate column, holes are drilled or punched in sizes ranging from 2.5 to 12 mm (5 mm being widely used). The hole pitch is normally ______________ times the hole diameter to give the required hole area?
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A. 0.5 to 1.5

B. 5 to 10

C. 2.5 to 4.0

D. 10 to 15

3711. Length to diameter ratio of most rotary driers is in the range of____________________?
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A. 10 to 20

B. 4 to 10

C. 1 to 2

D. 20 to 30

3712. In case of a shell and tube heat exchanger, the minimum shell thickness for carbon steel (inclusive of corrosion allowance) depends on shell diameter and is in the range of ________________ mm?
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A. 15-Aug

B. 5-Mar

C. 18-Dec

D. 5-11
3713. Rotary driers are most economically designed for the number of heat transfer units (HTU) from _________________?
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A. 5 to 10

B. 1.5 to 2.5

C. 0.01 to 1

D. 10 to 20

3714. In actual operation of a bubble cap distillation tower, the ______________ at the bottom of the tower is more than that at the top of the tower?
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A. All A., B. and C.

B. Pressure and temperature

C. Molal flow rate of vapour

D. Vapour molecular weight

3715. Of the pressure vessels, with same thickness but different diameters, which one withstands higher pressure ?
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A. Larger dia vessel

B. Strength of the vessel is same irrespective of the diameter

C. Larger dia long vessel

D. Smaller dia vessel
3716. The diameter of a propeller agitator used in agitation tank ranges from ____________ percent of the tank diameter and its peripheral speed is normally 300 to 500 metres/minute ?
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A. 15 to 30

B. 55 to 75

C. 40 to 50

D. 5 to 10

3717. In a ______________ riveted joint, the rivets in the various rows are opposite to each other?
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A. Chain

B. None of these

C. Zig-zag

D. Diamond

3718. Which of the following material is seldom used for pressure vessel construction ?
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A. Killed steel

B. Semi-killed steel

C. Rimmed still

D. Mild steel

3719. Pressure drop per tray in the atmospheric distillation column is about ________________ psi?
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A. 1 3

B. 0.5 1.0

C. 0.01 0.5

D. 0.07 0.12
3720. Flanges are connected to pipes by _______________________?
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A. All A., B. and C.

B. Screwing

C. Brazing

D. Welding

3721. The normal range of velocity of steam in pipes is _________________________ m/sec?
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A. 20-Oct

B. 0.1-0.5

C. 5-Jan

D. 80-100
3722. Holes of a sieve tray are arranged in triangular pitch of _________________ times the hole diameter?
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A. 2.5 to 5

B. 5 to 10

C. 10 to 15

D. 1.5 to 2

3723. A binary liquid Azeotropic mixture has boiling point lower than either of the components, when it shows _____________ deviation from Raoults Law?
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A. Negative

B. Positive

C. No

D. None of these

3724. Speed of industrial paddle agitator ranges from _____________ rpm?
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A. 20 to 100

B. 500 to 750

C. 1000 to 2000

D. 1 to 5

3725. ______________ of water makes it a widely used coolant in heat exchangers?
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A. Low viscosity

B. High specific heat

C. Low corrosiveness

D. Low dirt factor

3726. Normally, the plate thickness of the bottoms and roofs of vertically cylindrical storage vessels as compared to that of the cylindrical shell is____________?
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A. Less

B. More

C. More or less depending upon the pressure & temperature inside the vessel and the nature of

D. fluid contained therein

E. Same

3727. In a multipass shell and tube heat exchanger, the baffles on shell side is primarily provided for______________?
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A. Reducing scale deposition

B. Increasing pressure drop

C. Creating turbulence

D. Fixing the tubes

3728. Diameter of bubble caps used in high pressure columns is ______________ as compared to that used in identical vacuum columns?
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A. More

B. Same

C. Less

D. Either A. or B.; no generalisation can be made

3729. In case of a continuous distillation column, increase in reflux ratio may result in the______________?
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A. All A., B. and C.

B. Lower fixed charges for the column

C. Greater cost for the condenser coolant

D. Greater cost for the reboiler heat supply

3730. In a shell and tube heat exchanger having square pitch, the shell side equivalent diameter is given by (where, P = pitch, d = outside diameter of the tube) ?
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A. ?d/4P2

B. 4P2/?d

C. (P2 rd2/4)/rd

D. 4(P2 ?d2/4)/?d
3731. In distillation columns, bubble caps are held in place over trays by ________________?
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A. Rivets

B. A hold down bar

C. Bolts

D. Both B. and C.
3732. (Le/D) for fully open gate valves would be __________________?
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A. Much more than that for fully open globe valves

B. Much less (say 2% than that for fully open globe valves)

C. Around 7

D. Both B. and C.
3733. Joint efficiency (J) for a seamless pipe is_______________?
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A. 1.5

B. 1

C. < 0.5

D. 0.85

3734. At equal mass velocities, the values of film co-efficients for gases as compared to that for liquids are generally ?
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A. Lower

B. Same

C. Unpredictable

D. Higher

3735. Speed of the drum of the rotary vacuum filter normally ranges from _____________ rpm?
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A. 3 to 8

B. 8 to 15

C. 0.1 to 2

D. 5 to 7

3736. Reflux ratio variation in a distillation column is between___________________?
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A. Zero and infinity

B. Zero and one

C. None of these

D. Minimum and infinity
3737. With increase in the reflux ratio for a fixed production from a continuous binary distillation column, the ______________________ decreases?
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A. Fixed charges initially

B. Running cost of cooling water for condenser

C. Vapour & liquid load both

D. Running cost of steam for reboiler

3738. The dust collection efficiency of electrostatic precipitator increases with increase in the_________________?
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A. Gas flow rate

B. Electrode area

C. Both A. & B.

D. Neither A. nor B.

3739. Value of Peclet number = ?, is the representative of___________________?
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A. Plug flow

B. Eddy diffusivity = 0

C. Complete back mixing

D. Laminar flow

3740. Maximum size of the raschig rings used in a packed tower is about _______________ of the column diameter?
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A. 1/50th

B. 1/10th

C. 1/20th

D. 1/30th
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