Heat Transfer Miscellaneous


  1. Match List-I with List-ll and select the correct answer using the code given below the lists:
    List-I List-II
    A. Grashof number 1. Mass diffusion
    B. Schmidt number 2. Transient heat conduction
    C. Weber number 3. Free convection
    D. Fourier number 4. Forced convection
    5. Surface tension
    6. Radiation










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    NA

    Correct Option: B

    NA


  1. Grashof number signifies the ratio of









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    Grashof number = inertia force ×
    Buoyancy force
    (viscous force)2


    Correct Option: B

    Grashof number = inertia force ×
    Buoyancy force
    (viscous force)2




  1. The ratio of momentum diffusivity (υ) to thermal diffusivity (α), is called









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    Pr =
    μCp
    =
    ρVCp
    =
    V
    =
    V
    kkk / ρCpα

    Correct Option: A

    Pr =
    μCp
    =
    ρVCp
    =
    V
    =
    V
    kkk / ρCpα


  1. For the fluid flowing over a flat plate with Prandtl number greater than unity, the thermal boundary layer for laminar forced convection.









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    Pr1 / 3 =
    δ
    , if Pr > 1 , it means δ < δt
    δt

    Correct Option: A

    Pr1 / 3 =
    δ
    , if Pr > 1 , it means δ < δt
    δt



Direction: Heat is being transferred by convection from water at 48°C to a glass plate whose surface temp. is exposed to the water is at 40°C. The thermal conductivity of water is 0.6 W/mK and the thermal conductivity of glass is 1.2 W/mK. The spatial gradient of temperature in the water at the water-glass interface is dT/dy = 1 × 104 K/m.

  1. The heat transfer coefficient h in w/m2K is









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    For convection Heat flux, q = h(Tf – Ti)

    q = kw
    dT
    dyw

    = 0.6 × 1 × 104 = 6000 W/m
    ∴ h =
    q
    =
    6000
    = 750 W /m2K
    (Tf – Ti)8

    Correct Option: D

    For convection Heat flux, q = h(Tf – Ti)

    q = kw
    dT
    dyw

    = 0.6 × 1 × 104 = 6000 W/m
    ∴ h =
    q
    =
    6000
    = 750 W /m2K
    (Tf – Ti)8