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 jpcfd June 8, 2010 14:25

Microwave drying modeling

Hi,

Im trying to simulate the drying by microwave of different buildings material. A multiphysic problem with, electromagenetic, thermal and mass transfer coupled.
I treat the EM with a lambert law of energy penetration depending on the pemeabilty coupled with the moisture. The mass transfer i use a solid domain with liquid-vapour phases one attached and another (vapour) transported with a UDS diffusive equation.

I used a arrenious law to coupled the two phases ratio exchange and the traditional vapour saturation pressure with the desorption isotherm to calculate the quasistacionary equilibrium in each time step.

All is coupled in a multiple UDF schema.

I have detected from the diffusivity values obtained from the literature that i obtain overestimated drying times. The diffusivity value in the material pannel is in kg/m-s instead of m2/s, this mean that the diff coef is multiplied by the density?

I know that the transient term in the scalar transport equation is multiplied by the density but no the diffusive term.

I remake my calculations with the diffusive coefficent multiplied by the density and i obtain pretty close to the reality values. Also i check this on CFX that use traditional m2/s units.

Can any one explain this?