Dear MFiX Team or other users
Do you have any experiences about the sub-grid model in MFiX? I need to model the cooling tube in my simulation, and for this, the sub-grid modeling is necessary. I can’t clearly understand how I can implement the sub-grid model in the simulation after reading any theoretical journal paper. If you have any practical reference or information on the implementation of sub-grid modeling in MFiX, can you let me know?
Daniel Kim
Please provide more information on what you are going to simulate. Also, it is not clear how you define the “sub-grid model”?
The subgrid drag model is located in Model setup > Drag model in the MFiX program. If I select the Wen-Yu drag model, then in the Advanced part, the subgrid model is activated.
When it comes to the cooling tube modeling, I read one paper written by Xu, Zhijie, et al., whose full title is included below, and they used this subgrid model in MFiX simulation for the cooling tube modeling. They explained that the accuracy of simulation results could increase with coarser cells by using the sub-grid model. Also, when the array of cooling tubes are included in the system, and their volume is very small, the cooling cylinders can be replaced by a stationary, porous solids phase occupying an equivalent volume.
I can understand the objection of the subgrid model in the simulation based on the paper, but I can not find how I can implement this subgrid model for the cooling tube in the simulation. If you have any other example file or reference to show the practical usage of the subgrid model, it will be very helpful to me.
Xu, Zhijie, et al. “Predicting the performance uncertainty of a 1-MW pilot-scale carbon capture system after hierarchical laboratory-scale calibration and validation.” Powder technology 312 (2017): 58-66.
Since you are going to simulate both hydrodynamics and heat transfer on coarse grid, you need to use both filtered drag model and filtered heat transfer model.
1.Some filtered drag models, such as IGCI,MILIOLI drag models have already been implemented in MFiX. A recent filtered drag model that works for a wide range of fluidization region can be found in Gao et al.,2018. Development and validation of an enhanced filtered drag model for simulating gas-solid fluidization of Geldart A particles in all flow regimes,Chemical Engineering Science,184,2018,33-51.
2. The filtered heat transfer model has not been implemented in official version of MFiX yet. The model can be found in the paper doi:10.1115/IMECE2014-39964, you need to modify the heat transfer model in MFiX.