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Hi

I am fearly new in COMSOL. I want to solve heterogenoeus chemical reactor models. I am struggling to couple the fluid phase with the solid phase. For example the 1D heterogeneous model:
Fluid phase:
-us*dC/dz=kg*av*(C-Cs)
us*rho*cp*dT/dz=hf*av*(Ts-T)-Ua*(T-Tw)

Solid phase:
De/r^2*d/dr(r^2*dCs/dr)=ra*rho
lamda_e/r^2*d/dr(r^2*dTs/dr)=-delH*ra

These are standard reactor design equations. I want solve the solid phase equations at every point along the length of the fluid phase equations. I have made the solid phase dimensionless (as in axample of spherically symmetric transport), so that you can only solve in one direction using general PDE, as it is spherical particle.

Can anyone help me to couple the solid phase to solve the concentration and temperature of the solid phase and then send that value to the fluid phase at every point along the length of the reactor(fluid) phase direction. I have tried coefficient form pde as well as weak form pde for fluid phase, not sure which will be best for this application.

I have tried to make two seperate models, for solid and fluid, but cant seem to get to couple the variabels, COMSOL cant detect the variable from other model.

Any suggestions in what strategy to follow?
(I hope i am posting in the right topic area)