chemical engineering Mcqs
3601. Pressure drop (?p) and the superficial gas mass velocity (G) in case of packed absorption tower operating in the preloading range are related as_________________?
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A. ?p = G2

B. ?p = G0.5

C. ?p = 1/G0.6

D. ?p = G

3602. The safe distance of habitation from a hazardous chemical plant (TLV of its product < 1000 ppm) should be about ______________ kms?
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A. 1

B. 5

C. 15

D. 25
3603. The design stress, which is more than the damaging stress, is the least unit stress that will render a member unfit for service before the end of its normal life. The design stress factor or factor of safety indicates the margin between design stress and the _______________ stress?
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A. Working

B. None of these

C. Damaging

D. Allowable

3604. Log mean temperature difference in case of multi-pass shell and tube heat exchanger is always_________________?
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A. Less than arithmetic mean value

B. More than arithmetic mean value

C. More than geometric mean value

D. Both B. & C.

3605. For a cylindrical vessel of moderate height, the weld joint efficiency for joints parallel to the cylindrical axis is given as 1.0; while for joints along the girth (circumference) it is given as 0.8. In calculating the shell wall thickness using code formula for an internally pressurised cylindrical vessel, what value of weld joint efficiency should be used ?
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A. 0.9

B. (0.8)0.5

C. 0.8

D. 1

3606. ____________ head is the most economical for cylindrical vessels designed for operating at high pressure (> 15 atm.)?
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A. Ellipsoidal

B. Conical

C. Dished

D. Hemispherical

3607. For pipe flows, head is proportional to ______________ at constant capacity (where D = pipe diameter) ?
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A. 1/D5

B. D2

C. 1/D2

D. 1/D

3608. Steam side heat transfer co-efficient for design consideration under ordinary condition can be assumed to be about _____________ kcal/hr.m2.C?
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A. 7500

B. 15000

C. 1250

D. 2500

3609. The minimum plate spacing in most of the petroleum refinery distillation columns (of dia > 3 ft) is normally _____________ inches?
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A. 12

B. 18

C. 36

D. 6

3610. In condenser, the cooling water is passed in the tube side in a pass arrangement, because________________?
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A. More thinner tubes can be used

B. It makes condenser compact

C. It reduces heat transfer area

D. Pressure drop is reduced

3611. A cylindrical pressure vessel of volume 6 ?m3 has to be designed to withstand a maximum internal pressure of 10 atm. The allowable design stress of the material is 125N/mm2 and corrosion allowance is 2 mm. The thickness of the vessel for a length/diameter ratio of 3 will be close to________________?
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A. 8 mm

B. 6 mm

C. 10 mm

D. 5 mm

3612. For laminar flow (NRe < 2100) in steel pipe, the optimum inside pipe diameter is given by____________________?
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A. Di, opt = 3 Q0.36 ?0.18

B. Di, opt = 3 Q0.36 ?1.86 ?0.08

C. Di, opt = 3.9 Q0.45 ?0.23

D. Di, opt = 7.6 Q0.36 ?0.9

3613. The length of straight rectangular weir used on cross-flow trays is generally ________________ the column diameter ?
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A. 2 ft irrespective of (for column > 3 ft diameter)

B. Equal to

C. Twice

D. 0.6-0.8 times
3614. The shell side pressure drop in a shell and tube heat exchanger is maximum for _______________ baffle?
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A. Orifice

B. Disk and ring

C. Independent of the type of

D. Segmental

3615. In a shell and tube heat exchanger, the tube pitch is defined as the _____________________?
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A. O.D. of the tube for square pitch

B. Shortest centre to centre distance between adjacent tubes

C. Shortest distance between two adjacent tube holes

D. None of these

3616. Heat transfer co-efficient, hG(Kcal/hr.m2 .C) and mass velocity of air, G (kg/hr.m2 ) for air flow parallel to the surface in case of constant drying rate in batch drying is related as hG = 0.0176G0.8. But when the flow of air perpendicular to the surface is encountered, this equation changes to ____________________?
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A. 0.0176G1.37

B. 1.004G0.8

C. hG = 1.004G0.37

D. hG = 0.0176G0.37

3617. In a continuous distillation column, the optimum reflux ratio ranges from _______________ times the minimum reflux ratio?
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A. 2.7 to 3

B. 1.6 to 2

C. 2.2 to 2.6

D. 1.1 to 1.5
3618. Overall distillation column efficiency for most of the refinery columns can be given by (for ? = 0.07 1.4 cp and relative volatility < 4) (where ? = overall column efficiency, % ? = molal average viscosity of feed at average column temperature and pressure, cp ?p = pressure drop per tray, psi) ?
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A. ? = 17 61.1 log ?

B. ? = 1.66 0.25 log ?

C. ? = 24.6 (?p/?)

D. ? = 0.25 log ? 1.67

3619. Number of evaporators which can be used in service in a multiple effect evaporation system is limited by the__________________?
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A. Practical limit reached, due to low heat transfer rate because of inadequate temperature

B. ference

C. Economic limit reached, when the plant cost exceeds the saving of steam

D. Both A. & B.

E. Neither A. nor B.

3620. Saddle supports are used for supporting _____________ vessels?
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A. Thick walled vertical

B. Thick spherical

C. Horizontal cylindrical

D. Tall vertical

3621. _______________ shaped roof is most commonly used for cylindrical tanks ?
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A. Dome

B. Flat

C. Umbrella

D. Cone
3622. The ratio of volumes of the mixed reactor to the plug flow reactor (for identical feed composition, flow rate, conversion, and for all positive reaction orders) is always ?
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A. 1

B. > 1

C. Equal to the order of reaction

D. < 1

3623. _____________ dished head is the strongest of all?
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A. Hemispherical

B. Torispherical

C. Elliptical

D. None of these

3624. Corrosion allowance in the design of pressure vessel/chemical equipment is not necessary, if___________________?
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A. Plain carbon steel and cast iron parts are used

B. Wall thickness is > 30 mm

C. Material of construction is high alloy steel

D. Both B. & C.
3625. In a thin cylindrical shell, the hoop stress is ________________ stress?
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A. Radial

B. Circumferential tensile

C. Compressive

D. Longitudinal

3626. A single pass air heater is connected to a two pass unit. For the air flow rate and other conditions remaining the same, the film heat transfer co-efficient for air will vary in the ratio of_________________?
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A. 20.2

B. 2

C. 20.8

D. None of these

3627. Which of the following is used to set the diameter of the distillation column ?
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A. Static submergence

B. Number of theoretical plates

C. Length of straight rectangular weir on cross-flow tray

D. Allowable vapour velocity
3628. The function of manholes provided in the shell of a distillation column is to __________________?
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A. All A., B. and C.

B. Keep a check on the liquid gradient over the plate by direct visual observation

C. Give access to the individual trays for cleaning, maintenance and installation

D. Guard against foaming & entrainment by dumping antifoaming agent through it

3629. Frame thickness in the plate and frame filter press is normally in the range of ______________ inches?
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A. 1 to 5

B. 0.25 to 4

C. 1 to 12

D. 0.25 to 8
3630. Height of the flights in the rotary drier is in the range of___________________?
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A. 0.2 to 0.5 d

B. 0.02 to 0.05 d

C. 0.5 to 0.6 d

D. 0.08 to 0.12 d
3631. For a given design of bubble cap, the number of bubble caps to be used per tray is set by the _________________?
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A. Allowable gas velocity through the slots

B. All A., B. and C.

C. Plate spacing

D. Diameter of the column

3632. In the downcomer of a distillation column, the minimum recommended residence time is about _______________ seconds?
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A. 17.5

B. 2.5

C. 5

D. 12.5

3633. Tube side heat transfer co-efficient for turbulent flow of liquid through tubes is proportional to___________________?
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A. G0.8

B. G1.5

C. G0.2

D. G0.5

3634. Bubble cap tray is the most commonly used tray in large distillation column, because______________?
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A. None of these

B. It incurs less pressure drop as compared to any other try designed for the same duty

C. It eliminates the foaming and entrainment tendency during operation

D. Of its flexibility and nearly constant efficiency under varying conditions of operation
3635. Cylindrical pressure vessels in horizontal condition is generally supported on a ________________ support?
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A. Lug

B. Saddle

C. Skirt

D. Guy wire

3636. Pick out the wrong statement ?
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A. Flanged only head is a type of flat head in which gradual change in the shape at the centre results in reduced local stresses

B. In a flanged and shallow dished head, the crown radius is > shell outside diameter

C. In a flanged and standard dished head, the crown radius is ? shell outside diameter

D. Flat head covers are most suitable for larger vessels operating at very high pressure
3637. ____________ is the determining factor for the number of bubble caps to be used per tray?
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A. Tray diameter

B. Permissible slot velocity

C. Liquid load

D. Vapor load

3638. A cylindrical storage tank can have a self supported conical roof ?
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A. If its diameter is less than 15-20metres

B. Irrespective of its diameter

C. If its diameter is more than 50 meters

D. If the thickness of the roof is more than that of the cylindrical shell

3639. In case of a thin pressure vessel, the ratio of its diameter to wall thickness is_________________?
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A. < 10

B. > 20

C. 30

D. > 10
3640. For turbine agitator, the impeller diameter is about_________________?
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A. 0.3 to 0.5 d

B. 0.65 to 0.85 d

C. 0.1 to 0.2 d

D. 0.95 d

3641. In packed towers provided with pall rings liquid redistributors are positioned at heights of every 6 metres or 5-10 times the column diameter, whichever is less. Maximum size of the pall rings should not exceed _______________________ of the column diameter?
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A. 1/5-1/10th

B. 1/10-1/15th

C. 1/20-1/30th

D. 1/2 to 1/4th

3642. Width and depth of grooves in the tube sheet holes normally are _______________ inch respectively?
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A. 1/2 and 8

B. 1/64 and 1/8

C. 1/2 and 5

D. 1/8 and 1/64
3643. In which of the following evaporators, steam is fed inside the tube while the liquor is outside the tube ?
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A. Horizontal tube evaporator

B. Short tube vertical evaporator

C. None of these

D. Long tube vertical evaporator

3644. LMTD correction factor is used in heat exchanger design for____________________?
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A. Multipass shell and tube heat exchanger

B. Fouling fluids

C. Counter flow of hot and cold fluids

D. Double pipe heat exchanger

3645. Compensation against openings in process vessels for giving inlet and outlet connections, for providing sight glasses and manholes etc. is provided for strength and rigidity. The most efficient type of compensation is of _______________ type?
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A. Flared out

B. Ring plate

C. Fluid in

D. Nozzle or rim
3646. Correct use of factor of safety is very important in equipment design. It is defined as the ratio of the___________________?
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A. Ultimate stress to breaking stress

B. Working stress to ultimate stress

C. Ultimate stress to working stress

D. None of these

3647. Liquid redistribution should be done in a packed tower packed with raschig rings every 6 metres or ______________ times the column diameter, whichever is lower?
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A. 2.5-3.0

B. 10-12.5

C. 15-20

D. 5-7.5

3648. Vertical vessels are not supported by____________________?
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A. Columns

B. Skirts

C. Brackets

D. Saddles
3649. Factor of safety (i.e., overdesign factor) in heat transfer equipments is about _____________ percent more than the actual/theoretical design factor?
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A. 15-20

B. 35-40

C. 30-35

D. 10-May

3650. The ratio of linear stress to linear strain is termed as the ____________________?
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A. None of these

B. Bulk modulus

C. Modulus of rigidity

D. Modulus of elasticity