mass transfer in multiphase(fluent 6.2.16)

masood yooceframandi

hi friends!

I use fluent 6.2.16 to simulate a fluidized bed dryer(water+polypropylene+air):

"hot gas enters to vessel which contains wet polypropylene(water+polypropylene) and fluidizes that and heat transfer occures,then water in porouse polypropylene vaporizes and diffuses through polypropylene particle(in a particle not between particles)."

i want to simulate mass transfer of water vaopr through porous polypropylene but fluent 6.2.16 simulate only constant rate of mass transfer.but mass transfer through porouse particle is not constant rate.

what must i do?

any useful ans fast reply will be appreciated.

regards