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Chemical Engineering :: Heat Transfer

  1. Film boiling occurs at __________ pressure.

  2. A.
    atmospheric
    B.
    sub-atmospheric
    C.
    negative
    D.
    very high

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  3. Heat flux through several resistances in series in analogous to the current flowing through several

  4. A.
    resistances in parallel.
    B.
    capacitors in series.
    C.
    resistances in series.
    D.
    none of these.

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  5. Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the

  6. A.
    surrounding temperature.
    B.
    average temperature of the fin.
    C.
    temperature of the fin end.
    D.
    constant temperature equal to that of the base

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  7. Vacuum is generally maintained in the vapour space of an evaporator mainly to

  8. A.
    get economical temperature difference by using moderate pressure steam.
    B.
    facilitate forward feeding in multiple effect evaporation.
    C.
    concentrate heat sensitive materials.
    D.
    achieve very high concentration of the final product.

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  9. Double pipe heat exchangers are used

  10. A.
    when heat transfer area required is very high.
    B.
    when heat transfer area required is very low, i.e (100-200 ft2).
    C.
    because it occupies less floor area.
    D.
    because it is less costly.

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  11. Nusselt number (for forced convection heat transfer) is a function of the __________ number.

  12. A.
    Prandtl
    B.
    Reynolds
    C.
    both (a) & (b)
    D.
    neither (a) nor (b)

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  13. Pick out the wrong statement.

  14. A.
    Heat transfer by radiation can not occur across an absolute volume.
    B.
    In case of a shell and tube heat exchanger, the pressure drop through the shell is proportional to the number of times the fluid crosses the bundle between baffles.
    C.
    Propagation velocity for travel of heat radiation through vacuum is equal to the velocity of the light.
    D.
    The amount of heat involved in the condensation or vaporisation of 1 kg of a fluid is the same.

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  15. Which type of heat exchanger is preferred for heavy heat loads ?

  16. A.
    Double pipe
    B.
    Plate fine
    C.
    Series and parallel set of shell and tube
    D.
    None of these

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  17. Pick out the wrong statement.

  18. A.
    Reciprocal of the resistance to heat flow is called thermal conductance.
    B.
    Unit of thermal conductance is W/°K.
    C.
    Thermal conductance of a wall of thickness 'L', thermal conductivity 'k' and heat flow area 'A' is kL/A.
    D.
    none of these.

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