Chemical Engineering MCQs

Page No. 426

Pick out the wrong statement ?


aWith change in temperature, the radiant energy emitted by a black body remains unchanged

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bAbsorptivity of a body approaches unity in case of diffuse reflection

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cAbsorptivity of a perfectly black body is unity

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dValue of Stefan-Boltzmann constant is 4.876 × 10-8 KCal/m2.hr.°K4

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Pick out the wrong statement ?


aThe condensing film co-efficient is about 3 times lower for vertical condenser as compared to the equivalent horizontal condenser for identical situation

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bFilm co-efficient for vaporisation decreases as a result of vapor binding

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cIn industrial practice, sub-cooling of condensate is required, when the condensate is a volatile liquid and is to be transferred for storage

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dOverall heat transfer co-efficient in a heat exchanger is controlled by the value of the film coefficient, which is higher

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Pick out the wrong statement ?


aThe controlling resistance in case of heating of air by condensing steam is in the air fil

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bThe log mean temperature difference (LMTD) for counter flow and parallel flow can be theoretically same when any one of the fluids (hot or cold fluid) passes through the heat exchanger at constant temperature

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cIn case of a 1 – 2 shell and tube heat exchanger, the LMTD correction factor value increases sharply, when a temperature cross occurs

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dPhase change in case of a pure fluid at a given pressure from liquid to vapor or vice-versa occurs at saturation temperature

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Pick out the wrong statement?


aOrifice baffles are never used in a shell and tube heat exchanger

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bPressure drop on the shell side of a heat exchanger depends upon tube pitch also

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cIn a horizontal tube evaporator, surface blanketing by air is avoided

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dSplit ring type and pull through type floating heads are two commonly used floating heads is heat exchangers

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Pick out the wrong statement?


aReciprocal of the resistance to heat flow is called thermal conductance

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bUnit of thermal conductance is W/°K

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cThermal conductance of a wall of thickness ‘L’, thermal conductivity ‘k’ and heat flow area ‘A’ is kL/A

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dNone of these

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Pick out the wrong statement?


aSwenson-Walker crystalliser is a batch crystalliser

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bSuper saturation of the solution is the driving potential for a crystal growth

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cThe liquor left after the removal of crystals from a solution is called mother liquor

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dThe first stage of crystal formation is called nucleation

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Pick out the wrong statement ?


aHeat transfer by radiation cannot occur across an absolute volume

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bIn case of a shell and tube heat exchanger, the pressure drop through the shell is proportional to the number of times the fluid crosses the bundle between baffles

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cPropagation velocity for travel of heat radiation through vacuum is equal to the velocity of the light

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dThe amount of heat involved in the condensation or vaporisation of 1 kg of a fluid is the same

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Which of the following is correct ?


aRate = Driving force × Resistance

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bDriving force = Rate × Resistance

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cResistance = Driving force × Rate

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dRate = Resistance/Driving force

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Pick out the wrong statement ?


aSuperheated steam is preferably not used for process heating because of its low heat transfer film co-efficient

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bIn a shell and tube heat exchanger, the shell pressure drop is maximum for orifice baffles

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cS.I. unit of fouling factor is Watt/m2.°K

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dLongitudinal fins are used in extended surface heat exchangers, when the direction of fluid flow is parallel to the axis of the tube

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Pick out the wrong statement ?


aIn case of heat transfer by purely forced convection, GR/Re 2 ≤ 1

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bThe equivalent diameter of heat transfer for a duct of square cross-section (having each side as ‘x’) is equal to 4x

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cDistillation process is not the same as evaporation

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dThe effectiveness of nucleate boiling depends basically on the ease with which the bubbles are formed and detached from the heating surface

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