2 replies to this topic

[dianzz]

hello guys i wanna ask

from treybal book say : For steady-state mass transfer, the rate at which A reaches the interface from
the gas must equal that at which it diffuses to the bulk.liquid, so that no accumulation or depletion of A at the interface occurs.

i think the equation must be : N_A = k_y (Y_A,G-Y_Ai)=K_x(X_Ai-X_A,L)

TOTAL flux gas -> interface -> liquid = k_y (Y_A,G-Y_Ai) + K_x(X_Ai-X_A,L)

BUT i found in next sub chapter

TOTAL flux gas -> interface -> liquid BECOME :

N_A = K_y (Y_A,G-Y_A*) = k_y (Y_A,G-Y_Ai) + m.K_x(X_Ai-X_A,L)

i really dont understand. if somebody can help it would be great helpful

thanks before

[StefanCh]

I guess the first equation is about the liquid phase x ( K(x) ) and the last equation is about the gas phase y ( K(y) ).
This is why there is a correction in the last equation. I guess that m is the slope of the curve or the correction coefficient.
There is an addition in the last equation so that it adds up to make K_y (Y_A,G-Y_A*). Kx and Ky are not the same thing.

[markymaark]

I'd have to agree with Stefan.


Without further context I'd have to assume the next chapter takes more realistic approaches and thus corrects the first equation. I think the m, as Stephan said, is a slope correction since the concentration is not an instaneous change in the liquid (It is in gas phase, so no m). Thus it takes into consideration the gradual change in concentration from interface-> liquid and thus the flux change.

Mark