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Chemical Engineering :: Heat Transfer

  1. For large heat transfer area requirement, shell and tube heat exchanger is preferred, because it

  2. A.
    occupies smaller space.
    B.
    is more economical.
    C.
    is easy to operate and maintain.
    D.
    all (a), (b) and (c).

  3. Out of the following four assumptions used in the derivation of the equation for LMTD , which one is subject to the largest deviation in practice ?

  4. A.
    Constant overall heat transfer co-efficient.
    B.
    Constant rate of fluid flow.
    C.
    Constant specific heat.
    D.
    No partial phase change in the system.

  5. Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because

  6. A.
    convection becomes important
    B.
    conduction becomes important
    C.
    radiation becomes important
    D.
    sub-cooled boiling occurs

  7. Resistance to heat flow by conduction is proportional to (where, t & ρ are thickness & density of the material respectively and A = area normal to the direction of heat flow. )

  8. A.
    t
    B.
    1/ρ
    C.
    1/A
    D.
    all (a), (b) & (c)

  9. Temperature profile in steady state heat transfer is

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

  11. For the same heat load and mass flow rate in the tube side of a shell and tube heat exchanger, one may use multipass on the tube side, because it

  12. A.
    decreases the pressure drop.
    B.
    decreases the outlet temperature of cooling medium.
    C.
    increases the overall heat transfer coefficient.
    D.
    none of these.

  13. When vaporisation takes place through a blanketting film of gas, the phenomenon is termed as __________ boiling.

  14. A.
    pool
    B.
    nucleate
    C.
    transition
    D.
    film

  15. Minimum recommended baffle spacing in a shell and tube heat exchanger is about (where, D = shell diameter)

  16. A.
    0.2 D
    B.
    0.5 D
    C.
    0.66 D
    D.
    0.80 D

  17. Stefan-Boltzman law which describes the radiation heat transfer states that, it is proportional to (where, t = temperature in °C T = absolute temperature in ° K )

  18. A.
    t4
    B.
    T4
    C.
    1/t4
    D.
    1/T4

  19. The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe, where the wall heat flux is constant, is

  20. A.
    2.36
    B.
    4.36
    C.
    120.36
    D.
    dependent on NRe only