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Chemical Engineering :: Heat Transfer

  1. Hot water (0.01 m3 /min) enters the tube side of a counter current shell and tube heat exchanger at 80°C and leaves at 50°C. Cold oil (0.05 m3/min) of density 800 kg/m3 and specific heat of 2 kJ/kg.K enters at 20°C. The log mean temperature difference in °C is approximately

  2. A.
    32
    B.
    37
    C.
    45
    D.
    50

  3. In a heat exchanger, floating head is provided to

  4. A.
    facilitate cleaning of the exchanger.
    B.
    increase the heat transfer area.
    C.
    relieve stresses caused by thermal expansion.
    D.
    increase log mean temperature gradient.

  5. Leidenfrost point is a term concerned with the

  6. A.
    condensation of the saturated vapor on a cold surface.
    B.
    concentration of a corrosive solution by evaporation.
    C.
    heat transfer between two highly viscous liquids.
    D.
    boiling of a liquid on a hot surface.

  7. A process stream of dilute aqueous solution flowing at the rate of10 Kg.s-1 is to be heated. Steam condensate at 95°C is available for heating purpose, also at a rate of 10 Kg.s-1. A 1 - 1 shell and tube heat exchanger is available. The best arrangement is

  8. A.
    counter flow with process stream on shell side.
    B.
    counter flow with process stream on tube side.
    C.
    parallel flow with process stream on shell side.
    D.
    parallel flow with process stream on tube side.

  9. Heat produced when a steady state current, I passes through an electrical conductor having resistance, 'R' is

  10. A.
    IR
    B.
    I2R
    C.
    IR2
    D.
    I2R2

  11. Pick out the wrong statement.

  12. A.
    Orifice baffles are never used in a shell and tube heat exchanger.
    B.
    Pressure drop on the shell side of a heat exchanger depends upon tube pitch also.
    C.
    In a horizontal tube evaporator, surface blanketing by air is avoided.
    D.
    Split ring type and pull through type floating heads are two commonly used floating heads is heat exchangers.

  13. Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone.

  14. A.
    laminar
    B.
    transition
    C.
    both 'a' & 'b'
    D.
    highly turbulent

  15. The actual temperature drop across the heating surface in an evaporator depends on the

  16. A.
    feed.
    B.
    depth of liquid over heating surface.
    C.
    pressure difference between steam chest and vapour space.
    D.
    all (a), (b) and (c).

  17. Which of the following is not used as a medium for high temperature heating ?

  18. A.
    Dowtherm
    B.
    mercury
    C.
    liquid metal (e.g. molten sodium)
    D.
    fused salts (e.g., an eutectic mixture of 53% KNO3, 40% NaNO2and 7% NaNO3)

  19. Presence of a non-condensing gas in a condensing vapour

  20. A.
    increases the rate of condensation.
    B.
    decreases thermal resistance.
    C.
    is desirable to increase the film co-efficient.
    D.
    none of these.