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Chemical Engineering :: Heat Transfer

  1. Reason for operating an evaporator in multiple effect is to secure

  2. A.
    increased steam economy.
    B.
    decreased steam consumption.
    C.
    both (a) and (b).
    D.
    increased capacity.

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  3. In a cooling tower, water becomes cool by

  4. A.
    loosing sensible heat.
    B.
    heat transfer to surroundings.
    C.
    vaporisation due to heat loss to air.
    D.
    loosing latent heat.

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  5. In Fourier's law, the proportionality constant is called the

  6. A.
    heat transfer co-efficient
    B.
    thermal diffusivity
    C.
    thermal conductivity
    D.
    Stefan-Boltzman constant

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  7. The heat transfer co-efficient in film type condensation is __________ that for dropwise condensation.

  8. A.
    greater than
    B.
    lower than
    C.
    is same as
    D.
    half

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  9. Pick out the wrong statement.

  10. A.
    Bubble size increases with the dynamic viscosity of the liquid in case of nucleate pool boiling.
    B.
    Thermal conductivity of a dry material is more than that of the damp material.
    C.
    Ratio of its capacity to economy equals the steam consumption in kg/hr in an evaporator.
    D.
    Vaporisation of organic substances in evaporator mostly causes foam formation.

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  11. 'Duhring's plot' is of use in

  12. A.
    extractive distillation
    B.
    evaporation
    C.
    leaching
    D.
    absorption

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  13. Which has the lowest Prandtl number ?

  14. A.
    Liquid metal
    B.
    Aqueous solution
    C.
    Water
    D.
    Lube oil

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  15. Pick out the wrong statement.

  16. A.
    The value of hydrostatic head increases with increase in vacuum in the effect in a multiple effect evaporator system.
    B.
    Entering velocity of the liquid in the tubes of natural circulation evaporators is in the range of 0.3 to 0.9 metre/second.
    C.
    Duhring's plot is used for calculating the concentration of solution.
    D.
    In a multiple effect evaporation system, the number of effects is limited by the total boiling point rise.

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  17. Prandtl number for most of dry gases is about

  18. A.
    0.001
    B.
    0.72
    C.
    70
    D.
    150

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  19. Prandtl number is the reciprocal of

  20. A.
    Thermal diffusivity/Momentum diffusivity
    B.
    thermal diffusivity x Momentum
    C.
    Thermal diffusivity x Mass diffusivity
    D.
    Mass diffusivity x Momentum diffusivity

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