Chemical Engineering - Mass Transfer - Discussion
Discussion Forum : Mass Transfer - Section 3 (Q.No. 47)
47.
With increase in gas rate, the number of transfer units, NtoG, for a fixed degree of absorption by a fixed amount of solvent
Discussion:
2 comments Page 1 of 1.
Suraj said:
5 years ago
Option A is correct.
NtoG is defined as the ratio of change in vapour concentration to the average driving force to cause that change.
In the question it is given that degree of absorption of solute is fixed, so a change in vapour concentration will be fixed when the gas flow rate will be increased. But due to the increase in gas flowrate the average driving force decreases as the slope of the operating line (L/V) decreases. And this leads to an increase in NtoG.
Hope this helps you!
NtoG is defined as the ratio of change in vapour concentration to the average driving force to cause that change.
In the question it is given that degree of absorption of solute is fixed, so a change in vapour concentration will be fixed when the gas flow rate will be increased. But due to the increase in gas flowrate the average driving force decreases as the slope of the operating line (L/V) decreases. And this leads to an increase in NtoG.
Hope this helps you!
ShriRam said:
5 years ago
It should be option D.
H(toG) will increase with gas flow rate. N(toG) remains unaffected.
H(toG) = G/(Ky.a.(1-y)*m).
G = Gas flow rate.
Ky = mass transfer coefficient.
a = specific interface area(m2/m3 of packing).
(1-y) * m = [(1-y)-(1-y)]/ln[(1-y*)/(1-y)].
H(toG) will increase with gas flow rate. N(toG) remains unaffected.
H(toG) = G/(Ky.a.(1-y)*m).
G = Gas flow rate.
Ky = mass transfer coefficient.
a = specific interface area(m2/m3 of packing).
(1-y) * m = [(1-y)-(1-y)]/ln[(1-y*)/(1-y)].
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