Selecting the appropriate multiphase model and radiation model
 

Hello
I simulate the pneumatic transfer of -lets say- sand in a vertical furnace. The furnace walls are hot (approx 1300K) and the furnace geometry is simple, just a tube that is heated externally by resistances. the d/l ratio is 0.05 . I simulated successfully the air flow inside the tube. The flow goes downwards. Now i am trying to simulate the two phase flow (air and sand) that moves to the same direction(downwards). The volume fraction wont exceed 12% and i wanna know the particle trajectories in the furnace, particles temperature etc. I found that the most appropriate model that Fluent offers is DPM model. You agree with me?
In addition i wanna simulate the heat transfer from the hot walls to the particles. The main heat transfer mechanism now is not the same like before as air is not heated by radiation but by convection. Now i need to activate a radiation model..I have read that S2S can well simulate the heat transfer from the hot walls to the particles.. Do you agree with this? Any other idea about a model that would give me better results and require less computational time?
My last question has to do with the strategy i have to apply to treat my case.
I simulated the air flow (temperature and velocity are the most important properties for me) and now i am thinking of running the 2nd phase equations to determine the properties of the sand (time in the heater, trajectories, temperature vs time and length)
I am thinking of running the 2 phase flowe and finally activation the radiation model. You agree with this?
Thank you in advance. Your help is realy important for me
:)
Panos