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Chemical Engineering :: Heat Transfer

  1. Film boiling is usually not desired in commercial equipments, because

  2. A.
    the heat transfer rate is low in view of the large temperature drop.
    B.
    it is difficult to maintain.
    C.
    it is not economic.
    D.
    none of these.

  3. For the same heat transfer area and the terminal conditions, the ratio of the capacities of a single effect evaporator to a triple effect evaporator is

  4. A.
    3
    B.
    0.33
    C.
    1
    D.
    1.33

  5. The variation of thermal conductivity of a metal with temperature is often correlated using an expression of the form K = K0 + at. where, K is the thermal conductivity and T is the temperature (in °K). The units of 'a' in SI system will be

  6. A.
    W/m.k
    B.
    W/m
    C.
    W/m.k2
    D.
    none, 'a' is just a number

  7. Film condensation is promoted on a/an __________ surface.

  8. A.
    oily
    B.
    coated
    C.
    clean & smooth
    D.
    dirty

  9. Dietus-Boelter equation cannot be used for molten metals mainly due to its very low

  10. A.
    Prandtl number
    B.
    Grashoff number
    C.
    thermal conductivity
    D.
    viscosity

  11. If Prandtl number is greater than the Schmidt number, then the

  12. A.
    thermal boundary layer lies inside the concentration boundary layer.
    B.
    concentration boundary layer lies inside the thermal boundary layer.
    C.
    thermal & concentration boundary layers are of equal thickness.
    D.
    hydrodynamic(i.e., momentum)boundary layer is thicker than the other two.

  13. Which of the following accessories is provided in the vapor line of an evaporator for removing the entrained liquid ?

  14. A.
    Bleed point
    B.
    Vent
    C.
    Catchall
    D.
    Baffle

  15. Rate of heat transfer by vaporisation from pools of water is affected by the

  16. A.
    nature of heating surface and distribution of bubbles.
    B.
    surface tension of water.
    C.
    viscosity of water.
    D.
    all (a), (b) and (c).

  17. Multiple effect evaporators are commonly used in the manufacture of
    P. Paper Q. Superphosphate
    R. Sugar S. Fats

  18. A.
    P and Q
    B.
    P and R
    C.
    P and S
    D.
    R and S

  19. Which of the following has the highest thermal conductivity ?

  20. A.
    Brick
    B.
    Air
    C.
    Water
    D.
    Silver