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Mass Transfer - Engineering

Q1:

The surface renewal frequency in Danckwerts' model of mass transfer is given by (KL: mass transfer co-efficient)

A KL2.DA

B KL2.DA

C KL2/DA

D KL/DA2

ANS:A - KL2.DA

In Danckwerts' model of mass transfer, the surface renewal frequency (𝑓f) is given by: 𝑓=𝐾𝐿𝐷𝐴f=DA​KL​​ Where:

  • 𝐾𝐿KL​ is the mass transfer coefficient.
  • 𝐷𝐴DA​ is the diffusion coefficient of the solute in the bulk fluid.
So, the correct expression for the surface renewal frequency is: 𝐾𝐿𝐷𝐴DA​KL​​ None of the options presented match this expression exactly. However, option 3, 𝐾𝐿2𝐷𝐴DAKL2​, is the closest. To match the given options, you could rewrite the expression as 𝐾𝐿2𝐷𝐴DAKL2​, though it's not the conventional form for the surface renewal frequency in Danckwerts' model.