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Consider the following statements: For the laminar condensation on a vertical plate, the Nusselt theory says that 1. inertia force in the film is negligible compared to viscosity and weight 2. heat flow is mainly by conduction through the liquid film, convection in liquid film as well as in vapour is neglected. 3. velocity of vapour is very high Which of the above statements are CORRECT?

Consider the following statements: For the laminar condensation on a vertical plate, the Nusselt theory says that 1. inertia force in the film is negligible compared to viscosity and weight 2. heat flow is mainly by conduction through the liquid film, convection in liquid film as well as in vapour is neglected. 3. velocity of vapour is very high Which of the above statements are CORRECT? Correct Answer 1 and 2 only

Following were the assumptions in the Nusselt theory for the vertical plate:

  • The vapour is pure, dry, and saturated.
  • The condensate flow is under the action of gravity and is laminar.
  • The vapour at the liquid-vapor interface is stagnant so that there is no shear stress or drag on the flow of condensate.
  • The plate is maintained at a uniform temperature Tw that is less than the saturation temperature of the vapour Ts.
  • The liquid temperture at the interface is that of saturated vapour.
  • Fluid properties are constant.
  • Heat transfer across the condensate layer is by pure conduction, and the liquid temperature profile is linear.
  • Heat transfer is at a steady state.
  • The velocity of vapour is low or zero.
  • The acceleration of the condensate layer is negligible.

 

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