chemical engineering heat transfer chemical engineering MCQs – Page 10

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 Review each marked answer and report any item that may be outdated or unclear.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
181. Natural convection is characterised by__________________?
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A. Grashoff number

B. Peclet number

C. Reynolds number

D. Prandtl number

182. Which of the following is directly concerned with the heat transfer ?
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A. Sherwood number

B. Grashoff number

C. Euler number

D. Strouhal number

183. Three materials A, B and C of equal thickness and of thermal conductivity of 20, 40 & 60 kcal/hr. m. C respectively are joined together. The temperature outside of A and C are 30C and 100C respectively. The interface between B and C will be at a temperature of ____________ C?
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A. 70

B. 50

C. 95

D. 40

184. The heat transfer co-efficient in film type condensation is _______________ that for dropwise condensation?
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A. Half

B. Greater than

C. Is same as

D. Lower than
185. Radiator of an automobile engine is a ______________ type of heat exchanger?
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A. Cross-current

B. Co-current

C. Direct contact

D. Counter-current

186. Maximum water velocity in tubes of a 1-2 shell and tube heat exchanger may be around _____________ metres/second?
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A. 10

B. 20

C. 1

D. 30

187. When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is _______________?
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A. Free convection

B. Entry length problem in laminar forced conduction (developing thermal boundary layer)

C. Mixed convection (both free and forced)

D. Forced convection

188. A BTU/hr.ft.2 F is equal to_________________?
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A. None of these

B. 1 kcal/hr. m2.K

C. 4.88 kcal/hr. m.2C

D. 1 kcal/hr. m2C

189. LMTD for counter-flow and parallel flow heat exchanger will be the same, when the_________________?
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A. Cold fluid is heated to a certain temperature by condensing steam (isothermal fluid)

B. Outlet temperature of both the hot and cold fluid are same

C. Outlet temperature of hot fluid is less than the outlet temperature of the cold fluid

D. None of these

190. 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. 10

C. > 10

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

191. In forced convection, the heat transfer depends on _______________?
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A. Mainly Gr

B. Re, Pr

C. Re, Gr

D. Re only

192. The Graetz number is concerned with the___________________
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A. Absorption with chemical reaction

B. Heat transfer in laminar flow

C. Heat transfer in turbulent flow

D. Mass transfer between a gas and a liquid

193. Minimum recommended baffle spacing in a shell and tube heat exchanger is about (where, D = shell diameter)?
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A. 0.5 D

B. 0.2 D

C. 0.66 D

D. 0.80 D

194. The main purpose of providing fins on heat transfer surface is to increase the_________________?
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A. Heat transfer co-efficient

B. Temperature gradient

C. Heat transfer area

D. Mechanical strength of the equipment

195. Temperature profile in steady state heat transfer is________________?
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A. Linear

B. Parabolic

C. Asymptotic

D. Hyperbolic

196. The critical radius of insulation for cylindrical pipe is (where, hi = heat transfer coefficient at inside of the pipe) ?
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A. 2K/h0

B. hi/K

C. 2hi/K

D. K/h0
197. Maximum heat transfer rate is achieved in _____________ flow?
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A. Turbulent

B. Co-current

C. Counter-current

D. Laminar

198. The equivalent diameter for the annulus of a double pipe heat exchanger, whose inner pipe has fins on the outside is ______________ compared to the same size pipes without fins?
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A. Less

B. More

C. Same

D. Unpredictable

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

B. Viscous

C. Corrosive

D. Foaming

200. Tube expansion allowances exist in _____________ heat exchanger?
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A. U-tube

B. Single pass fixed tube sheet

C. None of these

D. Multipass fixed tube sheet