chemical engineering heat transfer chemical engineering MCQs – Page 24

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 Review each marked answer and report any item that may be outdated or unclear.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
461. Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the________________?
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A. Temperature of the fin end

B. Constant temperature equal to that of the base

C. Average temperature of the fin

D. Surrounding temperature

462. The heat flux in the nucleate boiling regimes is proportional to (where, ?T = excess temperature) ?
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A. (?T)4

B. (?T)2

C. (?T)3

D. ?(?T)

463. The sum of reflectivity and absorptivity for an opaque body is equal to____________________?
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A. 2

B. 0.5

C. 1

D. 0

464. Which of the following is not used as a medium for high temperature heating ?
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A. Fused salts (e.g., an eutectic mixture of 53% KNO3, 40% NaNO2and 7% NaNO3)

B. Dowtherm

C. Liquid metal (e.g. molten sodium)

D. Mercury
465. Thickness of thermal boundary layer is more compared to that of hydrodynamic boundary layer, when the value of Prandtl number is_________________?
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A. < 1

B. > 1

C. > 5

D. 1

466. Fouriers law of heat conduction applies to _____________ surfaces?
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A. Isothermal

B. Non-isothermal

C. Both A. and B.

D. Neither A. and B.

467. Double pipe heat exchangers are used__________________?
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A. Because it occupies less floor area

B. Because it is less costly

C. When heat transfer area required is very low, i.e. (100-200 ft2).

D. When heat transfer area required is very high

468. _______________ paint has the maximum absorption coefficient ?
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A. Grey

B. Yellow

C. White

D. Black
469. Steam side heat transfer co-efficient in an evaporator is in the range of ______________ kcal/hr.m2C?
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A. 100-500

B. 1000-1500

C. Oct-50

D. 5000-15000
470. In case of vertical tube evaporator, with increase in liquor level, the overall heat transfer co-efficient______________?
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A. May increase or decrease; depends on the feed

B. Decreases

C. Is not affected

D. Increases

471. For concentrating an aqueous solution of a material like anhydrous Na2SO4, whose solubility decreases with rise in temperature, the most suitable evaporator is a _______________ evaporator?
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A. None of these

B. High pressure

C. Vacuum

D. Backward feed

472. What is Nusselt number ?
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A. CP. ?/k

B. hD/k

C. CP. ?/h

D. h. CP/?

473. The unit of heat transfer co-efficient in SI unit is____________________?
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A. J/mK

B. W/mK

C. W/m2K

D. J/M2K

474. In case of a vertical tube evaporator, with increase in the liquor level, the___________________?
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A. Capacity of the evaporator is decreased

B. Capacity of the evaporator is increased

C. True temperature drop increases

D. Both B. and C.

475. Pick out the wrong statement?
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A. Thermal conductance of a wall of thickness L, thermal conductivity k and heat flow area A is kL/A

B. Unit of thermal conductance is W/K

C. Reciprocal of the resistance to heat flow is called thermal conductance

D. None of these

476. Steam is to be condensed in a shell and tube heat exchanger, 5 m long with a shell diameter of 1 m. Cooling water is to be used for removing the heat. Heat transfer co-efficient for the cooling water, whether on shell side or tube side is the same. The best arrangement is_____________?
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A. Vertical heat exchanger with steam on tube side

B. Horizontal heat exchanger with steam on shell side

C. Horizontal heat exchanger with steam on tube side

D. Vertical heat exchanger with steam on shell side
477. Crystallisation of solids from a homogeneous solution is a/an ______________ process?
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A. Mildly endothermic

B. None of these

C. Exothermic

D. Highly endothermic

478. The purpose of floating head in a heat exchanger is to_________________?
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A. Avoid buckling of tubes

B. Facilitate its lengthening, if needed

C. Provide support for tubes

D. Decrease the pressure drop

479. In forced circulation, the heating element is injected_________________?
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A. Internally

B. Externally

C. Both A. and A.

D. Neither A. nor B.

480. With the increase of temperature, the Col-burn jH factor_____________________?
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A. Decreases

B. Remains unchanged

C. Increases

D. May increase or decrease; depending on temperature