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Chemical Engineering :: Heat Transfer

  1. Unsteady state heat conduction occurs, when

  2. A.
    temperature distribution is independent of time.
    B.
    temperature distribution is dependent on time.
    C.
    heat flows in one direction only.
    D.
    three dimensional heat flow is concerned.

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  3. Mode of heat transfer in which the fluid moves under the influence of changes in fluid pressure produced by external work is called

  4. A.
    radiation
    B.
    natural convection
    C.
    forced convection
    D.
    conduction

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  5. Baffle spacing

  6. A.
    is not the same as baffle pitch.
    B.
    should be less than one fifth the diameter of the shell.
    C.
    should be less than the inside diameter of the shell.
    D.
    none of these.

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  7. Boiling point elevation of a solution of NaOH

  8. A.
    increases rapidly with temperature rise.
    B.
    is almost independent of temperature.
    C.
    is almost independent of pressure.
    D.
    both (b) and (c).

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  9. The advantage of backward feed multiple effect evaporators over forward feed units is that

  10. A.
    heat sensitive material can be handled.
    B.
    there is no additional cost of pumping.
    C.
    most concentrated liquid is at highest temperature.
    D.
    equal heat transfer co-efficients exist in various effects.

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  11. Which of the following is the most controlling factor for the rate of bubble detachment from the hot solid surface ?

  12. A.
    Liquid density
    B.
    Liquid viscosity
    C.
    Hot surface temperature
    D.
    Interfacial tension

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

  14. A.
    Corrosiveness
    B.
    Fouling characteristic
    C.
    Viscosity
    D.
    None of these

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  15. Thermal conductivities of most of the liquids __________ with rise in temperature.

  16. A.
    increases
    B.
    decreases
    C.
    remains unchanged
    D.
    may increase or decrease; depends on the liquid

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  17. A metal ball of radius 0.1 m at a uniform temperature of 90°C is left in air at 30°C. The density and the specific heat of the metal are 3000 kg/m3 and 0.4 kJ/kg.K respectively. The heat transfer co-efficient is 50 W/m2.K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60°C is

  18. A.
    555
    B.
    55.5
    C.
    0.55
    D.
    0.15

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  19. The purpose of floating head in a heat exchanger is to

  20. A.
    avoid buckling of tubes.
    B.
    provide support for tubes.
    C.
    decrease the pressure drop.
    D.
    facilitate its lengthening, if needed.

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