Possible bug in Fuchs-Knudsen evaporation model

Summary

Fuchs-Knudsen evaporation model instantly evaporates the active liquid phase. There is apparently a missing variable, particle surface area, in the calculation of the mass transfer according to the reference paper (Eq. 20 in https://doi.org/10.1016/j.jaerosci.2016.12.001). I made some calculation tests adding the particle surface area and then the model gives reasonable results.

Environment information

• OpenFOAM version : v2012
• Operating system : N/A
• Hardware info : N/A
• Compiler : N/A

Possible fixes

Adding particle surface area to the calculation on line 257 on $FOAM_SRC/lagrangian/intermediate/submodels/Reacting/PhaseChangeModel/LiquidEvapFuchsKnudsen/LiquidEvapFuchsKnudsen.C

-     // mass flux  [kg/s]
-     const scalar Ni = (rhog*Sherwood*Dab*Cm/d)*log((1 - YeInf)/(1 - YeSurf));
  
-     // mass transfer [kg]
-     dMassPC[lid] += Ni*dt;

+     // mass flux  [kg/m2/s]
+     const scalar Ni = (rhog*Sherwood*Dab*Cm/d)*log((1 - YeInf)/(1 - YeSurf));
  
+     // mass transfer [kg]
+     dMassPC[lid] += Ni*areaS*dt;

I passed areaS to the calculate function as this->areaS(d).