.ThermalSeparation.FilmModel.BaseClasses.EffectiveDiff

effective diffusivity method

Information

This model might only be used for diluted systems, i.e. in both phases there is one component which has a mole fraction close to one.

In this case the interactions between the components can be neglected and the molar flow rate of a component i only equals the mole fraction gradient of this specific component:


N_i=k_i * A * (x_i^star - x_i)

The variables k (mass transfer coefficient) and A (interfacial area) have to be determined in the extending classes, since their determination is column-type dependent.


Modelica Definition

The code definition for the molar flow rates is as shown below. If the stage is still in start-up modus, by definition all incoming vapour will condense, and a mass transfer equation is only needed on the liquid side. If there is no start-up modus, there is also a mass transfer equation for the vapour side.

for j in 1:n loop

// Vapour side

if considerStartUp and startUp[j] then

for i in 1:nSV loop

Ndot_v_interface[j,i] = if j==1 then -Vdot_v_in*c_v_in[i] else -Vdot_v[j-1]*c_v[j-1,i];

end for;

else

for i in 1:nSV loop

Ndot_v_interface[j,i]=k_v[j,i]*A_I[j]*propsVap[j].rho/propsVap[j].MM*(x_v_star[j,i]-x_v[j,i]);

end for;

end if;

// Liquid side

for i in 1:nSL loop

Ndot_l_interface[j,i]=k_l[j,i]*A_I[j]*propsLiq[j].rho/propsLiq[j].MM*(x_l_star[j,i]-x_l[j,i]);

end for;

end for;

Contents

NameDescription
 ThermoEquilibrium
 StateSelection
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