Page 60 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

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w 0. pa. c p(dta/h) = Ka e (t G -1^ ; (171)

Balance of the heat transfer through the interfacial area:

L. (h .*, (dti/dh) = K.a 0 (t G - fJ + r & (dxt/dh) ; (172)

Material balance through the interfacial area:

(173)

where Wg and the concentration of the evaporated or condensed component
are given by:

w 0 ^(hO+xJ/po, (174)

xJ. (175)

2
Gk is the mass flow of the dry gas - kg/(m .s);
Xf, - humidity of the gas related to the dry gas, kg/kg;
K G - mass transfer coefficient, m/s;
3
pa and pi - gas and liquid density, kg/m ;
c p and ci - gas and liquid heat capacity, J/(kg K);
% and ti - gas and liquid temperatures, °C;
2
K - heat transfer coefficient W/(m . K);
r- evaporation heat, J/kg.
The boundary conditions are:

h=0, fe=te/» t L=ti2, x h= x u; (176)

h=H,t G=t m, (177)

Instead of Eq. (177), the following condition can be also used:

h^Hj^tu, (178)

where the indices 1 and 2 are for the inlet and outlet.