chemical engineering MCQs – Page 181

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 Review each marked answer and report any item that may be outdated or unclear.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