chemical engineering heat transfer chemical engineering Mcqs
201. A perfect black body is a perfect _____________ of radiation?
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A. Absorber

B. Emitter

C. Both A. & B.

D. Neither A. nor B.

202. Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re 0.8. Pr n, is not valid, if the value of __________________?
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A. Reynolds number for the flow involved is > 10000

B. n = 0.4 is used for heating

C. n = 0.3 is used for cooling

D. Reynolds number for the flow involved is < 2100
203. In a 1-1 concurrent heat exchanger, if the tube side fluid outlet temperature is equal to the shell side fluid outlet temperature, then the LMTD is_________________?
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A. ?

B. Equal to the difference between hot fluid inlet temperature and cold fluid outlet temperature

C. Equal to the difference between hot and cold fluids inlet temperature

D. 0
204. jH factor for heat transfer depends upon the ____________ number?
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A. Prandtl

B. Biot

C. Nusselt

D. Reynolds
205. The units of resistance to heat transfer is _____________________?
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A. W-1m2K

B. J.m-2.K-1

C. J.m-1.K-1

D. W.m-2.K-1

206. In a shell and tube heat exchanger, the shell side fluid velocity can?t be changed by changing the_________________?
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A. Tube pitch

B. Tube diameter

C. Tube layout

D. Number of baffles

207. Sensible heat absorbed by 1 lb of water when it is heated from 32 to 212F may be around ______________ BTU?
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A. 180

B. Data insufficient, cant be predicted

C. 970

D. 3.97

208. One kilogram of water at 0C is changed to superheated steam of one atm pressure and 300 C. The major heat consumption in the process will be to________________?
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A. Data insufficient, cant be predicted

B. Heat the water from 0C to 100C

C. To superheat the steam

D. Evaporate the water
209. 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. 1/ V? -2

B. 1/V? -0.8

C. V? -2

D. V? -0.8

210. Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100C and the inside heat transfer coefficient is 3k/l. If the wall temperature on the outside is held at 25C, what is the inside wall temperature in degree centigrade ?
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A. 81.25

B. 35.5

C. 48.25

D. 43.75

211. Loss of heat from untagged steam pipe to the ambient air is by __________________?
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A. All A., B. & C.

B. Convection

C. Conduction

D. Radiation

212. Indirect contact heat exchangers are preferred over direct contact heat exchangers, because_________________?
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A. Heat transfer co-efficient are high

B. There is no mist formation

C. Cost of equipment is lower

D. There is no risk of contamination
213. Dropwise condensation is promoted on a/an ______________ surface?
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A. Glazed

B. Coated

C. Smooth

D. Oily
214. Which of the following has the lowest overall heat transfer co-efficient ?
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A. Dowtherm

B. Molten sodium

C. Air

D. Water

215. Open pan evaporators are preferred to be used, when the solution to be concentrated is_________________?
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A. Corrosive

B. Highly viscous

C. Salty

D. Scaling

216. A process stream of dilute aqueous solution flowing at the rate of10 Kg.s-1 is to be heated. Steam condensate at 95C is available for heating purpose, also at a rate of 10 Kg.s-1. A 1 1 shell and tube heat exchanger is available. The best arrangement is_______________?
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A. Counter flow with process stream on tube side

B. Parallel flow with process stream on shell side

C. Counter flow with process stream on shell side

D. Parallel flow with process stream on tube side

217. The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipe in laminar flow are_______________?
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A. Nu, Gz

B. Nu, Pr

C. Nu, Pr, Re

D. Re.Gz

218. In case of heat transfer by conduction in a hollow cylinder, ______________ mean area is used to calculate the heat transfer rate?
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A. Arithmetic

B. Geometric

C. Logarithmic

D. Either A., B. or C.

219. In case of a multipass shell and tube heat exchanger, the temperature drop in the fluid _______________?
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A. And the wall are proportional to individual resistances

B. And the wall is not related

C. None of these

D. Is inversely proportional to the resistance across which the drop occurs

220. The film co-efficient is decreased due to the presence of non-condensing gases in the vapors. The film co-efficient of superheated vapor as compared to that of saturated vapor is___________________?
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A. Some

B. More

C. Less

D. Either more or less; depends on the nature of vapor

221. In case of heat flow by conduction for a cylindrical body with an internal heat source, the nature of temperature distribution is_________________?
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A. Linear

B. Parabolic

C. Hyperbolic

D. None of these

222. In the free convection regime of pool boiling, the heat flux is proportional to__________________?
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A. ?t1/2

B. ?t2

C. ?t

D. ?t5/4
223. In Joules experiment, an insulated container contains 20 kg of water initially at 25C. It is stirred by an agitator, which is made to turn by a slowly falling body weighing 40 kg through a height of 4 m. The process is repeated 500 times. The acceleration due to gravity is 9.8 ms-2. Neglecting the heat capacity of agitator, the temperature of water (in C) is________________?
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A. 25

B. 40.5

C. 34.4

D. 26.8

224. A tank painted with which of the following coloured paints, would heat up maximum by radiation from sun ?
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A. Yellow paint

B. Grey paint

C. White paint

D. Black paint
225. The thickness of condensate layer in filmwise condensation depends on the__________________?
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A. All A., B. and C.

B. Condensation rate

C. Liquid flow rate from the surface

D. Surface configuration

226. Viscous & heat sensitive liquids are concentrated in _____________ evaporators?
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A. Open pan

B. None of these

C. Long tube

D. Agitated film
227. The equation, (NSt N2/3 Pr) = f/2, is the ____________ analogy ?
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A. Colburn

B. Prandtl

C. None of these

D. Reynolds

228. Plancks distribution law is valid for _____________ bodies?
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A. All A., B. & C.

B. Coloured

C. White

D. Black

229. The radiation heat flux from a heating element at a temperature of 800C, in a furnace maintained at 300C is 8 kW/m2. The flux, when the element temperature is increased to 1000C for the same furnace temperature is_____________________?
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A. 12.0 kW/m2

B. 11.2 kW/m2

C. 14.6 kW/m2

D. 16.5 kW/m2
230. Finned tube heat exchangers__________________?
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A. Give larger area per tube

B. Use metal fins of low thermal conductivity

C. Are used for smaller heat load

D. Facilitate very large temperature drop through tube wall

231. Trap is used to remove ________________ from steam pipe lines?
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A. Non-condensable

B. Steam

C. Condensate

D. None of these

232. With increase in temperature, the thermal conductivity of a gas ___________________?
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A. May increase or decrease depending on the type of gas

B. Decreases

C. Increases

D. Remain same

233. For hot feed, forward feeding as compared to backward feeding results in ______________ economy?
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A. No effect on

B. Increased

C. Decreased

D. None of these

234. A sphere of radius R1 is enclosed in a sphere of radius R2. The view (or shape) factor for radiative heat transfer of the outer sphere with respect to the inner sphere is ________________?
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A. (R1/R2)2

B. R2/(R1+R2)

C. 0

D. 1

235. Fresh orange juice contains 12% (by weight) solids and the rest water 90% of the fresh juice is sent to an evaporator to remove water and subsequently mixed with the remaining 10% of fresh juice. The resultant product contains 40% solids. The kg of water removed from 1 kg fresh juice is__________________?
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A. 0.7

B. 0.5

C. 0.4

D. 0.6

236. The film co-efficient between condensing vapour and metal wall increases with _____________________?
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A. Increasing temperature drop

B. Increasing viscosity of the film of condensate

C. Decreasing temperature of the vapour

D. Increasing temperature of the vapour
237. _____________ heat exchanger is used for chilling oil to be dewaxed?
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A. Fixed tube

B. U-tube

C. Double pipe

D. Floating head

238. With increase in temperature, the thermal conductivity of non-metallic amorphous solids_________________?
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A. Decreases

B. Remain constant

C. First decreases upto certain temperature and then increases

D. Increases
239. Multiple effect evaporators are commonly used in the manufacture of P. Paper Q. Superphosphate R. Sugar S. Fats ?
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A. R and S

B. P and S

C. P and Q

D. P and R

240. Nusselt number is the ratio of the ____________________?
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A. Temperature difference to the temperature gradient at the wall

B. Heat flux at the wall to that across the entire pipe

C. None of these

D. Temperature gradient of the wall to that across the entire pipe

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________________?
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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?
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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___________________?
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A. 25C

B. 40C

C. 35C

D. 30C

244. The steam ejector is used to__________________?
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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____________________?
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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___________________?
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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____________________?
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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?
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A. Sub-cooled

B. Film

C. None of these

D. Saturated nucleate

250. For a perfectly transparent surface (like gases), the____________________?
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A. All A., B. & C.

B. Transmissivity = 1

C. Absorptivity = 0

D. Reflectivity = 0