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Chemical Engineering :: Heat Transfer

  1. Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the

  2. A.
    existence of thermal boundary layer.
    B.
    temperature gradient produced due to density difference
    C.
    buoyancy of the bubbles produced at active nucleation site.
    D.
    none of these.

  3. Evaporator tubes are generally

  4. A.
    horizontal
    B.
    vertical
    C.
    inclined
    D.
    random

  5. For a counter current heat exchanger with Tih = 80°C, T°c = 60°C, T°h = 50°C and Tic = 30°C, and the temperature difference between the two streams being the same everywhere along Z, the direction of flow of hot fluid. The temperature profile should satisfy


  6. In a boiling curve, the peak heat flux is called the __________ point.

  7. A.
    Nusselt
    B.
    Leidenfrost
    C.
    boiling
    D.
    burnout

  8. Pick out the wrong statement.

  9. A.
    Heat transfer from a hot body to cold body by the emission of heat waves is called radiation:
    B.
    Filmwise condensation takes place on non-wettable surfaces.
    C.
    The boiling point of a solution is affected by liquid head as well as boiling point elevation.
    D.
    none of these.

  10. h.D/K is called the __________ number.

  11. A.
    Nusselt
    B.
    Peclet
    C.
    Rayleigh
    D.
    Grashoff

  12. Prandtl number is the ratio of

  13. A.
    mass diffusivity to thermal diffusivity.
    B.
    momentum diffusivity to thermal diffusivity.
    C.
    thermal diffusivity to mass diffusivity.
    D.
    thermal diffusivity to momentum diffusivity.

  14. Conductance is given by(where, x = thickness, A = heat flow area, K = thermal conductivity.)

  15. A.
    x/KA
    B.
    KA/x
    C.
    K/Ax
    D.
    A/Kx

  16. Heat flux, as defined in heat flow is analogous to __________ in electricity flow.

  17. A.
    current
    B.
    voltage
    C.
    resistance
    D.
    none of these

  18. The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, T = absolute temperature of the black body)

  19. A.
    αT
    B.
    α 1/T
    C.
    α T4
    D.
    independent of T