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Chemical Engineering :: Heat Transfer

  1. The purpose of providing expansion bellows in the shell of tubular exchanger is to

  2. A.
    increase the heating load.
    B.
    impart structural strength.
    C.
    account for the uneven expansion of shell and tube bundles.
    D.
    facilitate increase of shell length, if needed.

  3. A graph between __________ is called Wilson plot.

  4. A.
    B.
    C.
    v0.8 Vs . U
    D.

  5. Grashhoff number is given by

  6. A.
    gD3.β.Δtρ22
    B.
    gD2βΔtρ/μ2
    C.
    gD2βΔtP2μ
    D.
    gD3βΔtP2

  7. The overall heat transfer co-efficient for a shell and tube heat exchanger for clean surfaces is U0 = 400 W/m2.K. The fouling factor after one year of operation is found to be hd0 = 2000 W/m2.K. The overall heat transfer co-efficient at this time is

  8. A.
    1200W/m2.K
    B.
    894W/m2.K
    C.
    333W/m2.K
    D.
    287 W/m2.K

  9. In a laboratory test run, the rate of drying was found to be 0.5 x 10-3 kg/m2.s, when the moisture content reduced from 0.4 to 0.1 on dry basis. The critical moisture content of the material is 0.08 on a dry basis. A tray dryer is used to dry 100 kg (dry basis) of the same material under identical conditions. The surface area of the material is 0.04 m2/kg of dry solid. The time required (in seconds) to reduce the moisture content of the solids from 0.3 to 0.2 (dry basis) is

  10. A.
    2000
    B.
    4000
    C.
    5000
    D.
    6000

  11. Pick out the wrong statement.

  12. A.
    'Solvates' are chemical compounds formed by solute with their solvents. When water is the solvent, then it is called a 'hydrate'.
    B.
    In heat exchanger calculations (Δt)weighted is used in place of Δt, when it involves more than one sequence of heating or cooling i.e., desuperheating & condensation or condensation & sub-cooling.
    C.
    Heat transfer co-efficient during nucleate boiling is not influenced by the agitation imparted.
    D.
    In case of short tube vertical evaporators, area of central downtake is about 50 to 100% of the total tube cross-sectional area.

  13. What is the geometric mean of two heat transfer areas A1 and A2 ?

  14. A.
    A1 . A2
    B.
    A1 + A2
    C.
    A1 . A2
    D.
    2 A1 . A2

  15. Evaporation by thermocompression results in the

  16. A.
    saving of steam.
    B.
    realisation of multiple effect economy in a single effect.
    C.
    both (a) and (b).
    D.
    none of these.

  17. Forced circulation evaporators are normally used for concentrating liquids having

  18. A.
    scaling characteristics
    B.
    high viscosity
    C.
    both(a) & (b)
    D.
    neither (a) nor (b)

  19. Steam economy in case of a triple effect evaporator will be

  20. A.
    1
    B.
    < 1
    C.
    > 1
    D.
    between 0 and 1