Fluidised Bed Drying Simulation, TFM “Eulerian-Eulerian” Model

[Jayden Tang]

Hi all,

I’m currently modelling a fluidised bed dryer in ANSYS Fluent using the Eulerian–Eulerian approach. I’m using UDS to represent moisture in the gas and solid phases, with a UDF source term to transfer moisture from the solids into the gas.

I’m having trouble getting physically realistic mass transfer. At the moment, the predicted drying rate is extremely small, the solid moisture sometimes increases rather than decreases, and the mass transfer appears to occur only in small regions of the bed rather than throughout the solids. In some cases, the calculated drying driving force is negative across much of the domain.

I’ve been working through possible issues with the source-term sign, UDS boundary conditions, initialisation, saturation/equilibrium moisture calculation, mass-transfer coefficient and how the gas and solid UDS equations are coupled.

Has anyone implemented evaporation/drying between Eulerian phases using UDS in Fluent before?

I’d mainly appreciate some guidance on where my overall mass-transfer implementation may be going wrong, or what checks you would recommend to determine whether the problem is coming from the UDF formulation, UDS setup, boundary conditions or the underlying drying model.

Happy to share the UDF and Fluent setup if useful.