Page 28 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

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dG z = G z -G z+dz = D^dx.dy.dz.dr (64)
oz

The total increasing of the diffused component for the parallelepiped
volume is:

dG = dG x + dG + dG, = D| ^"T + ^ r + ^ r \dx.dy,dz.dT (65)
^ & dy & )

At steady state conditions the quantity of the diffused component in the
parallelepiped is constant. That means, the mass transferred by diffusion in it is
equal to the mass transferred outside with the moving fluid. Therefore, the
quantity of the component transferred through the walls is:

for dy dz

G x = w xC.dy.dz.dT ; (66)

for dxdz

G y=w yC.dx.dz.dt; (67)

for dxdy

G z = wCdx.dy.dr. (68)

Thus, the quantities transferred through the opposite walls are:

d(w C)
G x+dx = G, + dG = wCdy.dz.dx ^ —dx.dy.dz,dt (69)
dx
8(w C)
G v+dv =G V+ dG v = wCdx.dz.dr+ — dy.dz.dx, dt (70)
y y y y y Sy