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Chemical Engineering :: Heat Transfer

  1. Nucleate boiling is promoted

  2. A.
    on polished surfaces
    B.
    on rough surfaces
    C.
    in the absence of agitation
    D.
    none of these

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  3. In forced circulation, the heating element is injected

  4. A.
    internally
    B.
    externally
    C.
    both (a) and (a)
    D.
    neither (a) nor (b)

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  5. If all the conditions and dimensions are same, then the ratio of velocity through the tubes of a double pass heat exchanger to that through the single pass heat exchanger is

  6. A.
    1
    B.
    2
    C.
    1/2
    D.
    4

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  7. The equation, Nst = f/2, is the __________ analogy.

  8. A.
    Colburn
    B.
    Reynolds
    C.
    Prandtl
    D.
    none of these

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  9. Boiling point elevation for a strong and concentrated solution is found by Duhring's rule, which states that at the same pressure, the boiling point of a solution is a linear function of the __________ of pure water.

  10. A.
    boiling point
    B.
    dynamic viscosity
    C.
    kinematic viscosity
    D.
    density

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  11. Rate of crystallisation does not depend upon the

  12. A.
    extent of supersaturation.
    B.
    turbulence within the solution.
    C.
    number and active surface area of the crystals.
    D.
    none of these.

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  13. Stefen's block body radiation law can also be derived from __________ law.

  14. A.
    Kirchoffs
    B.
    Planck's
    C.
    Fourier's
    D.
    none of these

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  15. Multipass heat exchangers are used

  16. A.
    because of simplicity of fabrication.
    B.
    for low heat load.
    C.
    to obtain higher heat transfer co-efficient and shorter tube.
    D.
    to reduce the pressure drop.

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  17. A hollow sphere and a solid sphere of the same material and equal radii are heated to the same temperature. In this case,

  18. A.
    the cooling rate will be the same for the two spheres and hence the two spheres will have equal temperatures at any instant.
    B.
    both the spheres will emit equal amount of radiation per unit time in the beginning.
    C.
    both will absorb equal amount of radiation from the surrounding in the beginning.
    D.
    both(b) & (c).

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  19. Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m2 .°C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the

  20. A.
    higher condensing film co-efficient is desired.
    B.
    condensate is corrosive in nature.
    C.
    lower pressure drop through the exchanger is desired.
    D.
    temperature of the incoming vapor is very high.

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