chemical engineering Mcqs
4151. In a boiling curve, the peak heat flux is called the _____________ point?
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A. Boiling

B. Nusselt

C. Burnout

D. Leidenfrost
4152. Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the _____________ zone?
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A. Laminar

B. Transition

C. Both A & B

D. Highly turbulent
4153. The equivalent diameter for pressure drop is ________________ that for heat transfer?
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A. Not related with

B. Smaller than

C. Equal to

D. Greater than

4154. Heat transfer occurs by natural convection because change in temperature causes difference in__________________?
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A. Thermal conductivity

B. Density

C. Heat capacity

D. Viscosity

4155. Which is the most suitable for the concert-ration of highly concentrated solution ?
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A. Long tube vertical evaporator

B. Open pan evaporation

C. Agitated film evaporator

D. None of these

4156. When does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids ?
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A. At high fluid velocity

B. None of these

C. When fluid flows past a smooth surface

D. At low velocity

4157. Economy of a multiple effect evaporator is not influenced much by the_______________________?
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A. Boiling point elevations

B. Temperature of the feed

C. Rate of heat transfer

D. Ratio of the weight of the thin liquor to thick liquor

4158. The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)R and the co-efficient of performance as a heat pump (COP)HP are _______________?
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A. (COP)R = (COP)HP = 0.6

B. (COP)R = (COP)HP = 2.5

C. (COP)R = 2.5; (COP)HP = 1.5

D. (COP)R = 1.5; (COP)HP = 2.5
4159. With increase in temperature, the thermal conductivity of non-metallic amorphous solids_________________?
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A. First decreases upto certain temperature and then increases

B. Decreases

C. Increases

D. Remain constant

4160. Rate of heat transfer by vaporisation from pools of water is affected by the ____________________?
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A. Nature of heating surface and distribution of bubbles

B. Viscosity of water

C. All A., B. and C.

D. Surface tension of water

4161. The interchange factor for radiation heat transfer from surface x to surface y in case of an infinite parallel planes with emissivities ?x & ?y is given by_______________?
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A. ?x + ?y

B. 1/?x + 1/?y

C. ?x . ?y

D. (?x + ?y)/( ?x + ?y ?x . ?y)
4162. The variation of thermal conductivity of a metal with temperature is often correlated using an expression of the form K = K0 + at, where, K is the thermal conductivity and T is the temperature (in K). The units of a in SI system will be________________?
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A. W/m.k2

B. W/m

C. W/m.k

D. None, a is just a number

4163. The ratio of total radiating power to the absorptivity of the body depends upon the _____________ as per Kirchoff?s law?
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A. None of these

B. Temperature of the body

C. Wavelength of radiation

D. Nature of the body

4164. In case of vertical tube evaporator, with increase in liquor level, the overall heat transfer co-efficient______________?
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A. Is not affected

B. May increase or decrease; depends on the feed

C. Decreases

D. Increases

4165. Reynolds analogy states that (where, St = Stanton number f = friction factor) ?
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A. St = f/2

B. St = 4f

C. St = f/4

D. St = f1/2

4166. Unsteady state heat conduction occurs, when_______________?
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A. Heat flows in one direction only

B. Temperature distribution is dependent on time

C. Temperature distribution is independent of time

D. Three dimensional heat flow is concerned

4167. Circulation pump is located below the evaporator to___________________?
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A. Avoid cavitation

B. Create more suction head

C. None of these

D. Avoid frequent priming

4168. 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. Forced convection

D. None of these

4169. In a backward feed multiple effect evaporator ___________________ ?
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A. Feed is introduced in the first effect

B. No pumps are required between successive effects

C. Feed flows from low pressure to high pressure

D. None of these

4170. Double pipe heat exchangers are preferably useful, when____________________?
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A. High viscosity liquid is to be cooled

B. A corrosive liquid is to be heated

C. Requirement of heat transfer area is low

D. Overall heat transfer co-efficient is very high

4171. Analogy between mass and heat transfer is not applicable in case of____________________?
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A. Same velocity profile or equal eddy diffusivities

B. Thermal or pressure mass diffusion

C. Viscous heating or chemical reaction

D. Both B. and C.
4172. Steam side heat transfer co-efficient in an evaporator is in the range of ______________ kcal/hr.m2C?
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A. 100-500

B. 5000-15000

C. Oct-50

D. 1000-1500

4173. The steam ejector is used to__________________?
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A. Create vacuum

B. None of these

C. Superheat the steam

D. Remove condensate from the steam pipelines

4174. In case of a multipass shell and tube heat exchanger, providing a baffle on the shell side ______________ the heat transfer rate?
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A. May increase or decrease, depends on the type of baffle

B. Increases

C. Does not affect

D. Decreases

4175. Steam consumption in kg/hr in case of an evaporator is given by (where, C & E are capacity the economy of the evaporator respectively) ?
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A. C/E

B. 1/CE

C. CE

D. E/C

4176. A measure of the extent to which viscous heating is important relative to the heat flow resulting from the impressed temperature difference is represented by the _______________ number?
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A. Grashoff

B. Brinkman

C. Stanton

D. Condensation

4177. The type of liquor circulation system to be employed in evaporators (viz. natural or forced circulation) is determined mainly by the ______________ of the liquid?
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A. Corrosive nature

B. Thermal conductivity

C. Viscosity

D. Density

4178. If h1 = inner film co-efficient and /h2 = outer film co-efficient, then the overall heat transfer co-efficient is________________?
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A. Dependent on metal resistance

B. Always higher than h2

C. Always between h1 and h2

D. Always less than h1

4179. Which characteristic of a fluid is not important in deciding its route in a shell and tube heat exchanger ?
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A. Fouling characteristic

B. Corrosiveness

C. Viscosity

D. None of these
4180. The inside heat transfer co-efficient in case of turbulent flow of liquid in the tube side in a 1-2 shell and tube heat exchanger is increased by ______________ times, when the number of tube passes is increased to 8?
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A. 20.8

B. 40.4

C. 20.4

D. 40.8
4181. For gases, the thermal conductivity increases with temperature rise. For liquids, with increase in concentration, its thermal conductivity generally ?
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A. Remains unchanged

B. Decreases

C. Increases exponentially

D. Increases

4182. 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. 0.05

B. 0.15

C. 0.5

D. 0.1
4183. _____________ equation relates the thermal conductivity of a solid to its temperature ?
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A. Kistyakowsky

B. 217;s

C. Lees

D. Antoine

4184. A cube, sphere & a thin circular plate (all having same mass and made of same material) are all heated to 300C and allowed to cool in natural air. Which one will cool the slowest ?
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A. All will cool at the same rate

B. Plate

C. Cube

D. Sphere
4185. Thermal conductivity of a gas at low density, ___________ with increase in temperature ?
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A. Increases

B. May increase or decrease; depends on the gas

C. Decreases

D. Remains unchanged

4186. The critical radius r of insulation on a pipe is given by____________________?
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A. r = h/k

B. r = 2k/h

C. r = k/2h

D. r = k/h
4187. Overall heat transfer co-efficient for cooling of hydrocarbons by water is about_________________?
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A. 50 -100 W/m2.K

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

C. 50 -100 Kcal/hr.m2.C

D. 50 -100 BTU/hr. ft.2F
4188. Which of the following is not concerned with the heat transfer ?
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A. Peclet number

B. Stanton number

C. Brinkman number

D. Schmidt number
4189. Radiation heat losses from satisfactorily insulated high pressure boiler may be about _____________ percent?
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A. 7

B. 26

C. 18

D. 1

4190. For concentrating an aqueous solution of a material like anhydrous Na2SO4, whose solubility decreases with rise in temperature, the most suitable evaporator is a _______________ evaporator?
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A. None of these

B. Vacuum

C. Backward feed

D. High pressure

4191. Heat transfer by ____________ may not necessarily require the presence of a medium?
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A. Forced convection

B. Radiation

C. Conduction

D. Natural convection

4192. If a single tube pass heat exchanger is converted to two pass, then for the same flow rate, the pressure drop per unit length in tube side will ________________?
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A. Remain unchanged

B. Increase by 216

C. Increase by 1.8 times

D. Decrease by 22

4193. Colburn analogy is applicable for the value of Prandtl number from_________________?
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A. 0.6 to 120

B. 0.001 to 1

C. 0.5 to 5

D. 120 to 400

4194. Small scale evaporation is done in a_________________?
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A. Condenser

B. Heat exchanger

C. Multiple effect evaporator

D. Steam jacketed kettle
4195. In case of evaporators, liquid entrainment results primarily due to_________________?
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A. Foaming of the solution

B. High evaporation rate

C. High vacuum in the evaporator

D. High heat transfer rate

4196. Which of the following has the minimum thermal conductivity ?
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A. Carbon black

B. Nitrogen

C. Tar

D. Steel

4197. In SI units, fouling factor is expressed in __________________?
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A. W/m2K

B. m2K

C. mK/W

D. m2K/W
4198. 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.

4199. In a cooling tower, water becomes cool by________________?
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A. Loosing sensible heat

B. Loosing latent heat

C. Vaporisation due to heat loss to air

D. Heat transfer to surroundings

4200. For a multipass shell and tube heat exchanger, the LMTD correction factor is always________________?
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A. < 1

B. 1

C. > 1

D. Between 1 & 2