chemical engineering heat transfer chemical engineering MCQs – Page 13

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 Review each marked answer and report any item that may be outdated or unclear.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

241. For a laminar flow of fluid in a circular tube, h1 is the convective heat transfer co-efficient at velocity V1. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is________________?
0

A. 0.794 h1

B. 1.741 h1

C. 0.574 h1

D. 1.26 h1

242. Electro-magnetic spectrum range, which is important for radiation varies from _____________ microns?
0

A. 10 to 100

B. 100 to 1000

C. 1 to 100

D. 0.5 to 50

243. The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K = 0.04 W/m.K and thickness 0.16m is 10 W/m2. The temperature of the inside wall is 5C. The outside wall temperature is___________________?
0

A. 25C

B. 40C

C. 35C

D. 30C

244. The steam ejector is used to__________________?
0

A. Create vacuum

B. None of these

C. Remove condensate from the steam pipelines

D. Superheat the steam

245. Which is the most suitable for the concentration of foamy & frothy liquors ?
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A. None of these

B. Agitated film evaporator

C. Open pan evaporator

D. Long tube vertical evaporator

246. Prandtl and Reynolds analogy are same, when Prandtl number is____________________?
0

A. > 2

B. 1.5

C. 0.5

D. 1

247. For a counter current heat exchanger with Ti h = 80C, Tc = 60C, Th = 50C and Ti c = 30C, and the temperature difference between the two streams being the same everywhere along Z, the direction of flow of hot fluid. The temperature profile should satisfy___________________?
0

A. dT/dZ = 0

B. d2T/dZ2 = 0

C. d2T/dZ2 < 0

D. d2T/dZ2 > 0

248. If Prandtl number is greater than the Schmidt number, then the____________________?
0

A. Concentration boundary layer lies inside the thermal boundary layer

B. Thermal & concentration boundary layers are of equal thickness

C. Hydrodynamic (i.e., momentum) boundary layer is thicker than the other two

D. Thermal boundary layer lies inside the concentration boundary layer

249. Boiling of milk in an open vessel is an example of ______________ boiling?
0

A. Sub-cooled

B. Film

C. None of these

D. Saturated nucleate

250. For a perfectly transparent surface (like gases), the____________________?
0

A. All A., B. & C.

B. Transmissivity = 1

C. Absorptivity = 0

D. Reflectivity = 0

251. A hot liquid is kept in a big room. The logarithm of the numerical value of the temperature difference between the liquid and the room is plotted against time. The plot will be very nearly a/an___________________?
0

A. Circular arc

B. Straight line

C. Parabola

D. Ellipse

252. Fouling factor_____________________?
0

A. None of these

B. Is a dimensionless quantity

C. Does not provide a safety factor for design

D. Accounts for additional resistances to heat flow

253. Film boiling occurs at ________________ pressure?
0

A. Sub-atmospheric

B. Very high

C. Negative

D. Atmospheric

254. Asymptotic conditions is reached, when for a fluid flowing in laminar flow through a long tube___________________?
0

A. Exit-fluid temperature > wall temperature

B. Graetz number > 100

C. Exit fluid temperature < wall temperature

D. Exit fluid temperature = wall temperature

255. Black liquor generated during paper manufacture is concentrated in a___________________?
0

A. Single effect evaporator followed by a crystalliser

B. Multiple effect evaporator

C. Multiple effect evaporators followed by a crystalliser

D. Single effect evaporator

256. In a backward feed multiple effect evaporator ___________________ ?
0

A. Feed is introduced in the first effect

B. Feed flows from low pressure to high pressure

C. No pumps are required between successive effects

D. None of these

257. Film condensation is promoted on a/an _______________________ surface?
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A. Oily

B. Clean & smooth

C. Coated

D. Dirty

258. With increase in temperature, the thermal conductivity of steel___________________?
0

A. Increases exponentially

B. Increases

C. Remains unchanged

D. Decreases

259. In counter flow compared to parallel flow, ?
0

A. LMTD is greater

B. Less surface area is required for a given heat transfer rate

C. Both A. and B.

D. More surface area is required for a given heat transfer rate

260. Thermal conductivity of a conducting solid material depends upon its_______________?
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A. Temperature

B. Porosity

C. Both A. & B.

D. Neither A. nor B.

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