chemical engineering MCQs – Page 211

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 Review each marked answer and report any item that may be outdated or unclear.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
4201. A hot body will radiate heat most rapidly, if its surface is___________________?
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A. White & polished

B. White & rough

C. Black & rough

D. Black & polished

4202. Harmonic mean temperature difference is given by_________________?
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A. 2 (?T1 . ?T2)/(?T1 + ?T2)

B. (?T1 ?T2)/(?T1 . ?T2)

C. 2 (?T1 . ?T2)/(?T1 ?T2)

D. ?(?T1 . ?T2)

4203. Reynolds analogy states that_________________?
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A. Nst ? f

B. NNu ? f

C. Nst ? NRe

D. NRe ? f

4204. Prandtl number is the ratio of________________?
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A. Mass diffusivity to thermal diffusivity

B. Thermal diffusivity to momentum diffusivity

C. Thermal diffusivity to mass diffusivity

D. Momentum diffusivity to thermal diffusivity
4205. 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.

4206. During crystallisation, formation of crystal can occur in ______________ solution only?
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A. All A., B. and C.

B. Saturated

C. Supersaturated

D. Under-saturated

4207. The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, T = absolute temperature of the black body)?
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A. ?T

B. ? 1/T

C. Independent of T

D. ? T4

4208. Grashoff number, which is defined as g . ? (Ts T?) ?2. L3/?2, is proportional to the ratio of buoyancy force to ____________ force?
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A. Viscous

B. None of these

C. Elastic

D. Inertial

4209. In forced convection, the heat transfer depends on _______________?
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A. Re, Gr

B. Re only

C. Re, Pr

D. Mainly Gr

4210. Heat produced when a steady state current, I passes through an electrical conductor having resistance, R is___________________?
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A. I2R

B. IR

C. I2R2

D. IR2

4211. Fouling factor_____________________?
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A. Is a dimensionless quantity

B. Accounts for additional resistances to heat flow

C. Does not provide a safety factor for design

D. None of these

4212. The rate of heat transfer through a pipe wall is given by, q = 2? k (Ti T0)/ln (ri/r0). For cylinder of very thin wall, q can be approximated by__________________?
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A. q = 2? k (Ti T0)/[(r0 + ri)/2]

B. q = 2? k (Ti T0)/(r0/ri)

C. q = 2? ri k (Ti T0)/(r0/ri)

D. q = [2? k (Ti + T0)/2]/ln (ri/r0)

4213. Convective heat transfer, in which heat is transferred by movement of warmed matter is described by___________________?
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A. Newtons law of cooling

B. Ficks law

C. Fouriers law

D. None of these

4214. Heat transfer rate per unit area is called_________________?
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A. Heat transfer co-efficient

B. Thermal conductivity

C. Heat flux

D. Thermal diffusivity

4215. A black body when hot, emits heat radiation of _____________ wavelengths?
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A. One fixed

B. Large

C. All

D. Small

4216. Agitated film evaporator is suitable for concentrating _____________ liquids?
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A. Very thin

B. Foaming

C. Viscous

D. Corrosive

4217. Which of the following situations can be approximated to a steady state heat transfer system ?
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A. ntained constant at 180C

B. osed to atmospheric air at 35C</strong>

C. ospheric air at 35C

D. A sub-cooled refrigerant liquid at 8C flowing at the rate of 6 Kg/minute through a copper

E. A red hot steel slab (having outside surface temperature as 1300C) exposed to the

F. Boiling brine kept in open vessel when the bottom surface temperature of the vessel is

4218. Heat transfer by natural convection is enhanced in system with__________________?
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A. Low density change with temperature

B. High viscosity

C. Low temperature gradients

D. High co-efficient of thermal expansion
4219. A composite flat wall of a furnace is made of two materials A and B. The thermal conductivity of A is twice of that of material B, while the thickness of layer of A is half that of B. If the temperature at the two sides of the wall are 400 and 1200K, then the temperature drop (in K) across the layer of material A is________________?
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A. 133

B. 160

C. 125

D. 150

4220. What is the logarithmic mean of r1 and r2 ?
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A. (r1 r2)/-ln(r1/r2)

B. (r2 r1)/ln(r1/r2)

C. (r1 r2)/ln(r1/r2)

D. (r1 r2)/ln(r2/r1)