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Chemical Engineering :: Heat Transfer

  1. In a heat exchanger with steam outside the tubes, a liquid gets heated to 45°C, when its flow velocity in the tubes is 2 m/s. If the flow velocity is reduced to 1 m/s, other things remaining the same, the temperature of the exit liquid will be

  2. A.
    less than 45°C
    B.
    more than 45°C
    C.
    equal to 45°C
    D.
    initially decreases and remains constant thereafter.

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  3. For a liquid in laminar flow through a very long tube, when the exit fluid temperature approaches the wall temperature, the equation to be used is

  4. A.
    Nu = 0.023 Re0.8 . Pr0.4
    B.
    Nu = Gz
    C.
    Nu = Gz
    D.
    Nu = 2Gz0.5

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  5. Multiple effect evaporation accounts for

  6. A.
    steam economy
    B.
    lower operating costs
    C.
    investment economy
    D.
    none of these

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  7. In case of a supercooled solution, which is on the verge of crystallisation, the free energy of the solution as compared to that of the solid is

  8. A.
    more
    B.
    less
    C.
    same
    D.
    more or less; depends on the nature of solution

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  9. Maximum water velocity in tubes of a 1-2 shell and tube heat exchanger may be around __________ metres/second.

  10. A.
    1
    B.
    10
    C.
    20
    D.
    30

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  11. In Biot number, the characteristic length used is the ratio of the __________ of the solid.

  12. A.
    volume to surface area
    B.
    perimeter to surface area
    C.
    surface area to volume
    D.
    surface area to perimeter

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  13. Which of the following is the most widely used heat insulating material for pipelines carrying steam ?

  14. A.
    Tar dolomite bricks followed by asbestos.
    B.
    Fireclay refractory followed by aluminium sheet.
    C.
    Cotton followed by aluminium foil.
    D.
    85% magnesia cement and glass wool.

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  15. Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re0.8 . Prn, is not valid, if the value of

  16. A.
    n = 0.4 is used for heating.
    B.
    n = 0.3 is used for cooling.
    C.
    Reynolds number for the flow involved is > 10000.
    D.
    Reynolds number for the flow involved is < 2100.

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  17. Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids are clean and non-fouling ?

  18. A.
    Square pitch
    B.
    Triangular pitch
    C.
    Diagonal square pitch
    D.
    None of these

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  19. In case of a multipass shell and tube heat exchanger, the temperature drop in the fluid

  20. A.
    is inversely proportional to the resistance across which the drop occurs.
    B.
    and the wall are proportional to individual resistances.
    C.
    and the wall is not related.
    D.
    none of these.

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