Chemical Engineering MCQs

Page No. 474

Evaporator tubes are generally_____________________?


aHorizontal

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bVertical

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cInclined

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dRandom

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View Answer Vertical

In case of parallel flow heat exchanger, the lowest temperature theoretically attainable by the hot fluid is _____________ the outlet temperature of the cold fluid?


aEqual to

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bMore than

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cLess than

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dEither more or less than (depending upon the fluid)

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View Answer Equal to

Critical value of the _____________ number governs the transition from laminar to turbulent flow in free convection heat transfer?


aGrashoff

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bReynolds

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cBoth ‘a’ & ‘b’

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dPrandtl & Grashoff

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View Answer Prandtl & Grashoff

Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the_________________?


aExistence of thermal boundary layer

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bTemperature gradient produced due to density difference

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cBuoyancy of the bubbles produced at active nucleation site

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dNone of these

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View Answer None of these

Reason for operating an evaporator in multiple effects is to secure ___________________?


aIncreased steam economy

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bDecreased steam consumption

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cBoth A. and B.

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dIncreased capacity

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View Answer Both A. and B.

All analogy equations connecting friction factor and heat transfer co-efficient apply only to ___________________?


aWall or skin friction

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bForm friction

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cBoth A. and B.

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dTurbulent flow

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View Answer Wall or skin friction

Fouling factor for a heat exchanger is given by (where, U1 = heat transfer co-efficient of dirty surface U2 = heat transfer co-efficient of clean surface) ?


aU1 – U2

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b1/U1 – 1/U2

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c1/U2 – 1/U1

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dU2 – U1

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View Answer 1/U1 – 1/U2

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________________?


a1.26 h1

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b0.794 h1

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c0.574 h1

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d1.741 h1

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View Answer 0.794 h1

A graph between _____________ is called Wilson plot?


a(1/U) Vs. (1/v0.8)

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b(1/v0.8) Vs. U

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cv0.8 Vs . U

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d(1/U) Vs. (1/V)

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View Answer (1/U) Vs. (1/v0.8)

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 100°C and the inside heat transfer coefficient is „3k/l’. If the wall temperature on the outside is held at 25°C, what is the inside wall temperature in degree centigrade ?


a35.5

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b43.75

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c81.25

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d48.25

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View Answer 81.25

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