chemical engineering heat transfer chemical engineering MCQs – Page 23

Practise multiple-choice questions from chemical engineering heat transfer chemical engineering for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

chemical engineering heat transfer chemical engineering Mcqs
441. Which of the following has the minimum thermal conductivity ?
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A. Carbon black

B. Nitrogen

C. Steel

D. Tar

442. In a heat exchanger, floating head is provided to____________________?
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A. Facilitate cleaning of the exchanger

B. Increase the heat transfer area

C. Increase log mean temperature gradient

D. Relieve stresses caused by thermal expansion
443. Vacuum is generally maintained in the vapour space of an evaporator mainly to__________________?
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A. Achieve very high concentration of the final product

B. Concentrate heat sensitive materials

C. Get economical temperature difference by using moderate pressure steam

D. Facilitate forward feeding in multiple effect evaporation

444. For condensation of pure vapors, if the heat transfer co-efficients in filmwise and drop-wise condensation are respectively hf and hd, then__________________?
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A. hf > hd

B. hf = hd

C. hf < hd

D. hf could be greater or smaller than hd

445. What is the steam economy in case of a single effect evaporator system ?
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A. > 1

B. 1

C. < 1

D. 0.1

446. Value of Prandtl number for water ranges from_________________?
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A. 1 to 2

B. 5 to 10

C. 100 to 500

D. 1000 to 2000

447. In the equation Q = UA?t; ?t is_________________________?
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A. The difference of average bulk temperatures of hot and cold fluids

B. Logarithmic mean temperature difference

C. Arithmetic mean temperature difference

D. Geometric mean temperature difference

448. In a parallel flow heat exchanger, if the outlet temperature of hot and cold fluids are the same, then the log mean temperature difference (LMTD) is_________________?
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A. Minimum

B. Zero

C. Maximum

D. Infinity

449. Graetz number is given by__________________?
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A. mCp/k?

B. k?/mCp

C. mCp/kL

D. kL/mCp

450. The actual temperature drop across the heating surface in an evaporator depends on the_________________?
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A. Feed

B. Pressure difference between steam chest and vapour space

C. All A., B. and C.

D. Depth of liquid over heating surface

451. The value of Stefan-Boltzmann constant in SI unit is_________________?
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A. 0.1714 10-8W/m2.K4

B. 5.6697 10-8W/m2.K4

C. 5.6697 10-8kcal/m2. K4

D. 0.1714 10-8kcal/m2. K4

452. Duhring?s rule is important in solving problems on__________________?
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A. Evaporation

B. Humidification

C. Distillation

D. Crystallisation

453. While the total emissivity of a perfect black body is unity, the same for a real body is__________________?
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A. 0

B. > 1

C. Between 0 and 1

D. 1

454. _____________ heat exchanger is the most suitable, when the temperature of shell side fluid is much higher than that of tube side?
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A. U-tube

B. None of these

C. Three pass, fixed tube sheet

D. Single pass, fixed tube sheet

455. Analogy between mass and heat transfer is not applicable in case of____________________?
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A. Same velocity profile or equal eddy diffusivities

B. Thermal or pressure mass diffusion

C. Viscous heating or chemical reaction

D. Both B. and C.
456. The film thickness for laminar film condensation on vertical surface _____________ from top to bottom?
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A. And the surface conductance increase

B. Cumulatively increases

C. Cumulatively decreases

D. Remain constant

457. Among liquids, water has a comparatively high value of thermal conductivity, due to its__________________?
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A. Dense structure

B. High viscosity

C. Partial ionisation

D. Low density

458. In which mode of heat transfer, the Biot number is important ?
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A. Natural convection

B. Transient heat conduction

C. Radiation

D. Forced convection

459. Increasing the liquor level in the evaporator results in the_______________?
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A. Decreased capacity

B. Decreased effect of hydrostatic head

C. Increased true temperature drop

D. Increase in liquor film co-efficient

460. The critical radius r of insulation on a pipe is given by____________________?
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A. r = h/k

B. r = k/2h

C. r = 2k/h

D. r = k/h