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Chemical Engineering :: Heat Transfer

  1. The Graetz number is concerned with the

  2. A.
    mass transfer between a gas and a liquid.
    B.
    absorption with chemical reaction.
    C.
    heat transfer in turbulent flow.
    D.
    heat transfer in laminar flow.

  3. Solid angle subtended by the finite surface at the radiating element is

  4. A.
    called the view factor.
    B.
    called the angle of vision.
    C.
    proportional to the square of the distance between surfaces.
    D.
    expressed in terms of radians.

  5. Pick out the wrong statement.

  6. A.
    The emissivity of a surface decreases, if it gets corroded by atmospheric environment.
    B.
    The emissivity of a surface increases with increase in surface roughness.
    C.
    The emissivity of a polished surface is quite low.
    D.
    The emissivity of a non-metallic surface decreases with increase in the temperature.

  7. In forced convection, the heat transfer depends on

  8. A.
    Re, Pr
    B.
    Re, Gr
    C.
    mainly Gr
    D.
    Re only

  9. With increase in temperature, the thermal conductivity of most liquids

  10. A.
    increases
    B.
    decreases
    C.
    remains same
    D.
    first increases upto a certain temperature and then becomes constant

  11. Heat transfer by __________ may not necessarily require the presence of a medium.

  12. A.
    conduction
    B.
    natural convection
    C.
    forced convection
    D.
    radiation

  13. Pick out the correct statement.

  14. A.
    Higher is the temperature of the radiating body, higher is the wavelength of radiation.
    B.
    Logarithmic mean area is used for calculating the heat flow rate through a thick walled cylinder.
    C.
    The wavelength corresponding to maximum mono-chromatic emissive power increases with rise in temperature.
    D.
    Solid angle subtended by the finite surface at the radiating element is called the angle of incidence.

  15. In a shell and tube type heat exchanger, the floating tube bundle heat arrangement is used

  16. A.
    in low range of temperature differences.
    B.
    in high range of temperature differences.
    C.
    because of its low cost.
    D.
    to prevent corrosion of the tube bundles.

  17. Stefan-Boltzman law applies to __________ body.

  18. A.
    black
    B.
    white
    C.
    grey
    D.
    any colour

  19. The film co-efficient is decreased due to the presence of non-condensing gases in the vapors. The film co-efficient of superheated vapor as compared to that of saturated vapor is

  20. A.
    more
    B.
    less
    C.
    some
    D.
    either more or less ; depends on the nature of vapor