chemical engineering MCQs – Page 198

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 Review each marked answer and report any item that may be outdated or unclear.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

3941. Finned tube heat exchangers__________________?
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A. Facilitate very large temperature drop through tube wall

B. Give larger area per tube

C. Use metal fins of low thermal conductivity

D. Are used for smaller heat load

3942. For large heat transfer area requirement, shell and tube heat exchanger is preferred, because it________________?
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A. All A., B. and C.

B. Is easy to operate and maintain

C. Is more economical

D. Occupies smaller space

3943. Minimum tube pitch recommended for shell and tube heat exchangers is about _______________ times the outside diameter of the tube?
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A. 2.5

B. 1.25

C. 3.5

D. 1.75

3944. Which of the following is directly concerned with the heat transfer ?
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A. Grashoff number

B. Strouhal number

C. Euler number

D. Sherwood number

3945. A body cools down from 75C to 70C in 10 minutes. It will cool down from 70 C to 65 C in ______________ minutes?
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A. 10

B. Either B. or C., depends on the mass of the body

C. < 10

D. > 10

3946. Heat transfer by conduction in the turbulent core of a fluid flowing through a heated pipe is negligible, if the value of Prandtl number is_______________?
0

A. 0.4

B. 0.6

C. 0.8

D. 0.2

3947. Le/D) for 90 elbow (medium radius) and 90square elbow would be respectively around___________________?
0

A. 3 and 5

B. 25 and 60

C. 250 and 600

D. 100 and 250

3948. Steam economy in case of a triple effect evaporator will be _________________?
0

A. > 1

B. < 1

C. 1

D. Between 0 and 1

3949. Pressure differential maintained across a continuous rotary vacuum filter is in the range of _______________ mm Hg column?
0

A. 250 to 500

B. 600 to 700

C. 100 to 150

D. 50 to 100

3950. A BTU/hr.ft.2 F is equal to_________________?
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A. 1 kcal/hr. m2C

B. 4.88 kcal/hr. m.2C

C. 1 kcal/hr. m2.K

D. None of these

3951. Tube height in a calandria type evaporator is normally less than _______________ metres?
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A. 3.5

B. 2

C. 5.5

D. 1

3952. Boiling point of a solution according to Duhrings rule is a linear function of the _____________ of water?
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A. Density

B. Thermal conductivity

C. Boiling point (at the same pressure)

D. Viscosity

3953. Radiation energy is emitted by all the substances, which are above____________________?
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A. 0K

B. 100C

C. Room temperature

D. 0C

3954. A forced circulation long tube vertical evaporator as compared to the natural circulation evaporator__________________?
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A. Is economical in operation

B. Employs high velocity, high heat transfer rate and less heating surface requirement

C. Employs a centrifugal pump placed between external downtake from vapor drum and inlet to

D. e bundle

E. Both B. & C.

3955. Evaporator tubes are generally_____________________?
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A. Inclined

B. Random

C. Horizontal

D. Vertical

3956. Fouling factor for a heat exchanger is given by (where, U1 = heat transfer co-efficient of dirty surface U2 = heat transfer co-efficient of clean surface) ?
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A. 1/U1 1/U2

B. 1/U2 1/U1

C. U1 U2

D. U2 U1

3957. The thermal boundary layer at NPr > 1 ?
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A. Is thinner than hydrodynamic boundary layer

B. Is thicker than hydrodynamic boundary layer

C. Disappears

D. And the hydrodynamic boundary layers are identical

3958. Peclet number (Pe) is given by____________________?
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A. Pe = Re.Pr

B. Pe = Nu.Re

C. Pe = Re/Pr

D. Pe = Pr/Re

3959. An ejector is used to__________________?
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A. Remove condensate

B. Increase pressure

C. Increase temperature

D. None of these

3960. In a forward feed multiple effect evaporator unit__________________?
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A. No pump is required to withdraw the product from the last effect

B. Viscosity of liquid is highest in first effect

C. Transfer from effect to effect is done by pumps

D. None of these

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