[Yuting]

Hi friends,

I am doing a project of modelling the fixed bed particles drying process. In my reactor the particles initially contain 10% moisture and packed at the bottom, the entered gas is just air with 1000K. When the hot gas encounter the cold bed, the particles is heated up then water will released as vapor. The vapor will condense at the cooler particle surface. I use Euler-Granular method to model such system. During I modeling this process, I write an udf defining the rate of evaporation and condensation and make the assumption that evaporation only take place when the solid phase reach the boiling point that equal to 373.15K and works well. But actually the evaporation process take place not only at 373.15K, it is driven by the concentration gradient between the particle surface and bulk phase.
Fluent has provided an example of heterogeneous reaction rate udf for defining the evaporation and condensation of a droplet. But when I try to introduce this model into my case, solution always divergence at species equation and I still struggle with the first part of this example udf, which defines a function to calculate the saturation of pressure. Does anybody have experience dealing with such problem??