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

KL/DA²
√(KL².DA)
KL²/DA
KL².DA

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Mass Transfer
Pick out the wrong statement pertaining to leaching.

Very high temperature is not needed for the leaching of sugar beet
Vegetable seeds can be leached in either of Bollman extractor, Rotocel or Kennedy extractor
Fine solids can not be leached in a Pachuka tank
Door classifier can be used for leaching of coarse solids

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Mass Transfer
In case of absorption with exothermic reaction, for fluids having

Pr = Sc; percentage change in heat and mass transfer flux will be the same for a given change in the degree of turbulence
Pr = Sc ; there won
Both A & B
Pr = Sc = 1; total mass, momentum and thermal diffusivity will be the same

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