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Mass Transfer - Engineering

Q1:

The velocity, concentration and temperature boundary, for the boundary layer development on a flat plate during connective mass transfer will be same, if

A NSc = 1

B NSc = NPr = NLe

C NPr = NLe

D NSc = NLe

ANS:B - NSc = NPr = NLe

The velocity, concentration, and temperature boundary layers for the boundary layer development on a flat plate during convective mass transfer will be the same if: NSc = NPr = NLe In this equation:

  • 𝑁𝑆𝑐NSc is the Schmidt number, representing the ratio of momentum diffusivity to mass diffusivity.
  • π‘π‘ƒπ‘ŸNPr is the Prandtl number, representing the ratio of momentum diffusivity to thermal diffusivity.
  • 𝑁𝐿𝑒NLe is the Lewis number, representing the ratio of thermal diffusivity to mass diffusivity.
When the Schmidt number (𝑁𝑆𝑐NSc), Prandtl number (π‘π‘ƒπ‘ŸNPr), and Lewis number (𝑁𝐿𝑒NLe) are all equal, it implies that the diffusivities of momentum, heat, and mass are in the same proportion. Under these conditions, the thicknesses of the velocity, concentration, and temperature boundary layers will be similar, leading to a similarity solution for the boundary layer equations, and the velocity, concentration, and temperature profiles will be identical. Therefore, if 𝑁𝑆𝑐=π‘π‘ƒπ‘Ÿ=𝑁𝐿𝑒NSc=NPr=NLe, the velocity, concentration, and temperature boundary layers will be the same during convective mass transfer on a flat plate.