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Chemical Engineering :: Heat Transfer

  1. Intermittant tube cleaning is possible to be done in case of a __________ evaporator.

  2. A.
    basket type
    B.
    horizontal tube
    C.
    calendria
    D.
    none of these

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  3. Harmonic mean temperature difference is given by

  4. A.
    ΔT1 . ΔT2
    B.
    C.
    D.

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  5. Arithmetic mean area can be used in heat transfer problem to calculate the heat flow by conduction through a cylinder which is

  6. A.
    thin walled having the value of Ao Ai/< 2.
    B.
    thick walled.
    C.
    having the value of Ao/Ai > 2.
    D.
    both (b) and (c).

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  7. Three solid objects of the same material and of equal mass-a sphere, a cylinder (length = diameter) and a cube are at 500°C initially. These are dropped in a quenching bath containing a large volume of cooling oil each attaining the bath temperature eventually. The time required for 90% change in temperature is the smallest for

  8. A.
    cube
    B.
    cylinder
    C.
    sphere
    D.
    equal for all the three

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  9. Overall heat transfer co-efficient for cooling of hydrocarbons by water is about

  10. A.
    50 -100 Kcal/hr.m2.°C
    B.
    50 -100 W/m2 . °K
    C.
    50 -100 BTU/hr. ft.2°F
    D.
    1000 - 1500 BTU/hr. ft.2°F

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  11. Absorptivity of a perfect black body is unity. Which of the following has maximum absorptivity ?

  12. A.
    aluminium foil
    B.
    refractory bricks
    C.
    iron plate
    D.
    coke breeze

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  13. Thermal diffusivity is given by

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  15. At what value of Prandtl number, the hydrodynamic and thermal boundary layers of a fluid flowing over a heated plate will be identical ?

  16. A.
    1
    B.
    < 1
    C.
    > 1
    D.
    none of these

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  17. Fourier's law of heat conduction applies to __________ surfaces.

  18. A.
    isothermal
    B.
    non-isothermal
    C.
    both (a) and (b)
    D.
    neither (a) and (b)

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  19. __________ chart is known as transient heat conduction chart.

  20. A.
    Dirhing's
    B.
    Heisler's
    C.
    Mollier's
    D.
    Cox

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