chemical engineering MCQs – Page 208

Practise multiple-choice questions from chemical engineering for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

chemical engineering Mcqs
4141. For a cold dilute feed to produce thick viscous liquor, backward feeding as compared to forward feeding results in_____________________?
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A. Increased economy

B. Decreased economy

C. No effect on economy

D. Lower capacity

4142. Thermal diffusivity is given by__________________?
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A. ?/hCp

B. ?Cp/a

C. k/?Cp

D. ?Cp/k

4143. Evaporation by thermo compression results in the _________________________?
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A. Saving of steam

B. Realisation of multiple effect economy in a single effect

C. Both A. and B.

D. None of these

4144. In an interphase heat transfer process, the equilibrium state corresponds to equality of temperature in the two phases, while the condition for equilibrium in an interphase mass transfer process is equality of___________________?
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A. Chemical potentials

B. Concentrations

C. Activity co-efficients

D. Mass transfer co-efficients

4145. A wall has two layers of materials A and B; each made of a different material. Both the layers have the same thickness. The thermal conductivity of material A is twice that of B. Under the equilibrium, the temperature difference across the wall is 36C. The temperature difference across the layer A is ______________ C?
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A. 24

B. 18

C. 6

D. 12
4146. 1 BTU/hr.ft.F is equal to _____________ kcal/hr. m.C?
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A. 1.49

B. 1

C. 4.88

D. None of these

4147. At what value of Prandtl number, the hydrodynamic and thermal boundary layers of a fluid flowing over a heated plate will be identical ?
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A. None of these

B. 1

C. 1
4148. Natural convection is characterised by__________________?
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A. Prandtl number

B. Reynolds number

C. Peclet number

D. Grashoff number
4149. The actual temperature drop across the heating surface in an evaporator depends on the_________________?
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A. All A., B. and C.

B. Depth of liquid over heating surface

C. Feed

D. Pressure difference between steam chest and vapour space

4150. Vacuum is generally maintained in the vapour space of an evaporator mainly to__________________?
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A. Get economical temperature difference by using moderate pressure steam

B. Achieve very high concentration of the final product

C. Concentrate heat sensitive materials

D. Facilitate forward feeding in multiple effect evaporation

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