[Benzaa]

Hi, I was wondering if you could give me some advise regarding modeling of two phases system.

In my system, there is a solid reacting with a gas that is flowing inside the equipment. I have already developed a code that simulates the solution but, due the mass interaction between the gas and solid, the sum of the mass fractions is not always one.

I am addressing this problem by adjusting the density of the gas and solid with a mass balance and not with the ideal gas law. I havent finished the code, but, while working on it I found something that I would like to have some advise about it.

What I have done is to discretise the mass balance equation:

d(Rho)/dt + d(Rho Vel)/dx = S

into this with an upwind approach

(Ap)(RhoP) = (Ae)(RhoE) + (Aw)(RhoW) + Sc

where:

Aw = max( VelW*Area, 0)
Ae = max( -VelE*Area, 0)
Ap = Aw + Ae + (VelE * Area - VelW * Area) + dt/dv - Sp
Sc = Sdt + dt/dv (Rho`)

My question is, in the central coefficient (Ap), when I use the term (VelE * Area - VelW * Area) the solution doesnt make sense at all.

When it is removed, the solution makes more sense. What could be the reason for that? and, is this a good approach for the solution of a reacting system like this one??

Please, any help will be appreciated