chemical engineering heat transfer chemical engineering MCQs – Page 14

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 Review each marked answer and report any item that may be outdated or unclear.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

261. In evaporators, lowering the feed temperature_______________?
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A. Increases the heating area required

B. Reduces the economy

C. Both A. and B.

D. Decreases the heating area required

262. Conduction occurs in the buffer zone for a fluid flowing through a heated pipe, only when Prandtl number is________________?
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A. > 1

B. 0.1

C. < 1

D. 1

263. 200 kg of solids (on dry basis) is subjected to a drying process for a period of 5000 seconds. The drying occurs in the constant rate period with the drying rate as, Nc = 0.5 10-3 kg/m2.s. The initial moisture content of the solid is 0.2 kg moisture/kg dry solid. The interfacial area available for drying is 4 m2/1000 kg of dry solid. The moisture content at the end of the drying period is (in kg moisture/kg dry solid)?
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A. 0.5

B. 0.15

C. 0.05

D. 0.1

264. A fluid is flowing inside the inner tube of a double pipe heat exchanger with diameter d. For a fixed mass flow rate, the tube side heat transfer co-efficient for turbulent flow conditions is proportional to_____________________?
0

A. d0.8

B. d-0.2

C. d-1

D. d-1.8

265. jH factor for heat transfer is not a function of the _______________ number?
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A. Reynolds

B. Nusselt

C. Grashoff

D. Both B. & C.

266. The most conducive surface for dropwise condensation to occur is the _____________ surface?
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A. Oily

B. Smooth

C. Coated

D. Glazed & polished

267. A hot body will radiate heat most rapidly, if its surface is___________________?
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A. Black & polished

B. Black & rough

C. White & rough

D. White & polished

268. Convective heat transfer, in which heat is transferred by movement of warmed matter is described by___________________?
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A. Ficks law

B. Fouriers law

C. None of these

D. Newtons law of cooling

269. Intermittent tube cleaning is possible to be done in case of a _____________ evaporator?
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A. Basket type

B. Calandria

C. Horizontal tube

270. If air (a non-condensing gas) is present in a condensing vapor stream, it will ______________ the condensation rate of vapor?
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A. Increase the condensing film co-efficient as well as

B. Increase

C. Not affect

D. Decrease

271. Which type of heat exchanger is preferred for heavy heat loads ?
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A. Series and parallel set of shell and tube

B. Plate fine

C. None of these

D. Double pipe

272. Controlling heat transfer film co-efficient is the one, which offers ______________ resistance to heat transfer?
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A. Lower

B. The largest

C. No

D. The least

273. Multiple effect evaporation is generally recommended, when the______________________?
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A. Large scale evaporation of liquor is needed

B. Fuel is cheaply available

C. Evaporation on small scale is to be done

D. Corrosive liquids are to be concentrated

274. Overall heat transfer co-efficient for cooling of hydrocarbons by water is about_________________?
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A. 50 -100 Kcal/hr.m2.C

B. 1000 1500 BTU/hr. ft.2F

C. 50 -100 BTU/hr. ft.2F

D. 50 -100 W/m2.K

275. The outlet temperature of cooling water in a heat exchanger is generally not allowed to exceed above 50C in industrial practice mainly to avoid_________________?
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A. Excessive corrosion

B. Its evaporation loss

C. Decrease in heat exchanger efficiency

D. Uneconomic LMTD

276. An evaporator while concentrating an aqueous solution from 10 to 40% solids evaporates 30000 kg of water. The amount of solids handled by the system in kg is___________________?
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A. 9000

B. 4600

C. 4000

D. 3000

277. Mode of heat transfer involved in the cooling of air cooled internal combustion engine is_________________?
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A. Natural convection

B. Conduction

C. None of these

D. Forced convection

278. 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. Conduction

B. Forced convection

C. Radiation

D. Natural convection

279. A metal ball of radius 0.1 m at a uniform temperature of 90C is left in air at 30C. The density and the specific heat of the metal are 3000 kg/m3 and 0.4 kJ/kg.K respectively. The heat transfer co-efficient is 50 W/m2.K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60C is_________________?
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A. 555

B. 0.55

C. 55.5

D. 0.15

280. Pick out the wrong statement?
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A. The liquor left after the removal of crystals from a solution is called mother liquor

B. Swenson-Walker crystalliser is a batch crystalliser

C. Super saturation of the solution is the driving potential for a crystal growth

D. The first stage of crystal formation is called nucleation

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