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Chemical Engineering :: Heat Transfer

  1. Pick out the wrong statement.

  2. A.
    By increasing the number of shell passes, the temperature cross in a shell and tube heat exchanger can be prevented.
    B.
    An underdesigned steam trap will back up the condensate instead of discharging it out.
    C.
    Steam condensate is corrosive because of the presence of dissolved oxygen in it.
    D.
    Film boiling is desirable in commercial equipments due to high heat transfer rate at low temperature drop.

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  3. Graetz number is given by

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  5. For a cold dilute feed to produce thick viscous liquor, backward feeding as compared to forward feeding results in

  6. A.
    increased economy
    B.
    decreased economy
    C.
    lower capacity
    D.
    no effect on economy

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  7. Economy of an evaporator is influenced by the

  8. A.
    steam pressure
    B.
    feed temperature
    C.
    number of effect
    D.
    both(b) & (c)

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  9. If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows __________ law.

  10. A.
    hyperbolic
    B.
    parabolic
    C.
    linear
    D.
    logarithmic

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  11. In regenerative air preheater (as practised in heating of coke ovens), the heat is transferred

  12. A.
    through a metallic wall.
    B.
    by direct contact of hot flue gas with air.
    C.
    by heating an intermediate material (like chequor bricks) and then heating the air from this hot material.
    D.
    none of these.

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  13. __________ equation relates the thermal conductivity of a solid to its temperature.

  14. A.
    Antonie
    B.
    Kopp's
    C.
    Lee's
    D.
    Kistyakowski

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  15. For small temperature difference, the heat transfer rate as per Newton's law of cooling is proportional to (where, Δt = excess temperature)

  16. A.
    Δt
    B.
    Δt2
    C.
    Δt3
    D.
    Δt

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  17. Pick out the wrong statement.

  18. A.
    The condensing film co-efficient is about 3 times lower for vertical condenser as compared to the equivalent horizontal condenser for identical situation.
    B.
    Film co-efficient for vaporisation decreases as a result of vapor binding.
    C.
    In industrial practice, sub-cooling of condensate is required, when the condensate is a volatile liquid and is to be transferred for storage.
    D.
    Overall heat transfer co-efficient in a heat exchanger is controlled by the value of the film co-efficient, which is higher.

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  19. Viscous & heat sensitive liquids are concentrated in __________ evaporators.

  20. A.
    open pan
    B.
    long tube
    C.
    agitated film
    D.
    none of these

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