chemical engineering MCQs – Page 192

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 Review each marked answer and report any item that may be outdated or unclear.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
3821. LMTD for evaporators & condensers for a given terminal parameters & set of conditions for counter-flow is equal to that for parallel flow. In such heat exchangers, with one of the fluids condensing or evaporating, the surface area required is the least in the ______________ flow?
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A. Mixed

B. Counter flow

C. Parallel

D. Same in either A , B. or C.
3822. Shortest distance between two tubes is___________________?
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A. Called tube clearance

B. Called tube pitch

C. None of these

D. More in case of triangular pitch as compared to square pitch of tube layout

3823. When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is _______________?
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A. Free convection

B. Entry length problem in laminar forced conduction (developing thermal boundary layer)

C. Mixed convection (both free and forced)

D. Forced convection

3824. In case of parallel flow heat exchanger, the lowest temperature theoretically attainable by the hot fluid is _____________ the outlet temperature of the cold fluid?
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A. Either more or less than (depending upon the fluid)

B. Less than

C. Equal to

D. More than

3825. The unit of conductance in SI unit is_______________?
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A. W/m2

B. W/mK

C. W/K

D. W/m

3826. Corrosiveness of steam condensate is due to the presence of________________?
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A. CO2

B. Dissolved O2

C. Both A. & B.

D. Neither A. nor B.

3827. With increase in temperature, the thermal conductivity of most liquids_________________?
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A. Remain same

B. Decreases

C. Increases

D. First increases upto a certain temperature and then becomes constant

3828. Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids are clean and non-fouling ?
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A. Triangular pitch

B. Diagonal square pitch

C. None of these

D. Square pitch

3829. The normal range of velocity of water in pipes is _______________ m/sec?
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A. Oct-50

B. 15-30

C. 0.1-0.5

D. 1-2
3830. The ratio for the rate of washing to the final rate of filtration in a washing type of plate and frame filter is____________________?
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A. 0.25

B. 0.75

C. 1.25

D. 0.5

3831. For hot feed, forward feeding as compared to backward feeding results in ______________ economy?
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A. No effect on

B. None of these

C. Decreased

D. Increased
3832. Dittus-Boelter equation used for the determination of heat transfer co-efficient is valid ___________________?
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A. For liquid metals

B. For fluids in turbulent flow

C. When Grashoff number is very important

D. For fluids in laminar flow

3833. LMTD cant be used as such without a correction factor for the_________________?
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A. Condensation of mixed vapour in a condenser

B. Multipass heat exchanger

C. All A. B. and C.

D. Baffled heat exchanger

3834. Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re 0.8. Pr n, is not valid, if the value of __________________?
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A. Reynolds number for the flow involved is > 10000

B. Reynolds number for the flow involved is < 2100

C. n = 0.3 is used for cooling

D. n = 0.4 is used for heating

3835. Normal screwed fittings are used for pipes upto a diameter of _______________ inches?
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A. 9

B. 5

C. 1.5

D. 3
3836. A multiple effect evaporator as compared to a single effect evaporator of the same capacity has _________________?
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A. Lower heat transfer area

B. Higher steam economy

C. Lower steam economy

D. Higher solute concentration in the product

3837. The capacity of double-effect evaporator is less than half of the capacity of two single effects, each of which is operating over same terminal temperature difference, when the________________ ?
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A. Solution has an elevation of boiling point

B. Evaporators operate at atmospheric pressure

C. Evaporators operate under vacuum

D. None of these

3838. Which of the following has the lowest overall heat transfer co-efficient ?
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A. Molten sodium

B. Air

C. Water

D. Dowtherm

3839. Multipass heat exchangers are used______________________?
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A. To obtain higher heat transfer co-efficient and shorter tube

B. Because of simplicity of fabrication

C. To reduce the pressure drop

D. For low heat load

3840. In most of the shell and tube heat exchangers, the tube pitch is generally ______________ the tube diameter?
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A. one-fourth of

B. 1.25-1.50 times

C. 2.5 times

D. Less than