chemical engineering MCQs – Page 213

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 Review each marked answer and report any item that may be outdated or unclear.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

4241. Radiation heat transfer rates does not depend upon the_________________?
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A. Surface area and temperature of the heat source

B. Distance between the heat source and the object receiving the heat

C. None of these

D. Type of absorbing surface

4242. As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient ?
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A. Goes through a maximum

B. Continues to increase

C. Continues to decrease

D. Goes through a minimum

4243. The rate of emission of radiation by a body does not depend upon the__________________?
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A. Surface temperature of the body

B. Shape and porosity of the body

C. Wavelength of radiation

D. Nature of the surface

4244. The ratio of momentum diffusivity to thermal diffusivity is the ______________ number?
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A. Nusselt

B. Grashoff

C. Stanton

D. Prandtl

4245. When vaporisation takes place through a blanketting film of gas, the phenomenon is termed as ___________________ boiling?
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A. Transition

B. Nucleate

C. Pool

D. Film

4246. Electromagnetic radiations propagate in vacuum with a velocity of _______________ metre/second?
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A. 3 108

B. 3 1012

C. 3 105

D. 3 1010

4247. Which of the following has the minimum absorptivity ?
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A. Refractory bricks

B. Iron plates

C. Aluminium foil

D. Coal dust

4248. In case of _____________ boiling, the bubbles formed on a submerged hot surface get absorbed in the mass of the liquid?
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A. Pool

B. Nucleate

C. Low pressure

D. None of these

4249. For an ideal black body______________________?
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A. Transmissivity = 1

B. Reflectivity = 1

C. Emissivity = 0

D. Absorptivity = 1

4250. Nusselt number (for forced convection heat transfer) is a function of the _____________ number?
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A. Prandtl

B. Reynolds

C. Both A. & B.

D. Neither A. nor B.

4251. Dittus-Boelter equation cannot be used for molten metals mainly due to its very low_____________________?
0

A. Prandtl number

B. Thermal conductivity

C. Viscosity

D. Grashoff number

4252. The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by__________________?
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A. Roughening the surface

B. Painting the surface black

C. Giving the surface a mirror finish

D. Painting the surface white (with aluminium paint)

4253. In case of surface condensers, a straight line is obtained on plotting 1/U vs. ____________ on an ordinary graph paper?
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A. V? -0.8

B. 1/V? -0.8

C. 1/ V? -2

D. V? -2

4254. The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface) ?
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A. K/h0

B. 2K/h0

C. h0/K

D. h0/2K

4255. In the reaction, Ca + 2H2O = Ca(OH)2 + H2; what volume (c.c.) of hydrogen at STP would be liberated, when 8 gm of calcium reacts with excess water ? (Atomic weight of calcium = 40) ?
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A. 4480

B. 0.4

C. 1120

D. 2240

4256. Pick out the correct conversion?
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A. 1 calorie = 252 BTU

B. 1 BTU = 252 calories

C. 1 BTU =453.6 calories

D. 1 calorie = 453.6 BTU

4257. Absorptivity of a perfect black body is unity. Which of the following has maximum absorptivity ?
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A. Refractory bricks

B. Aluminium foil

C. Iron plate

D. Coke breeze

4258. Mode of heat transfer in which the fluid moves under the influence of changes in fluid pressure produced by external work is called_______________?
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A. Radiation

B. Conduction

C. Forced convection

D. Natural convection

4259. The molecular velocity of a real gas is proportional to (where, T = absolute temperature of the gas)?
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A. T

B. 1/?T

C. ?T

D. T2

4260. Solutions having the same osmotic pressure are called _____________ solutions?
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A. Isotonic

B. Ideal

C. Saturated

D. Dilute

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