DEM:Why the particles suspend in the air

MFiX How to
#1

Hello everyone,
I have a DEM case which simulates the fluidized bed.
gas_and_solid_2019-10-31T150007.840204.zip (372.2 KB)

Now I have two problems:

  1. the particles stop in the air, neither being blown up, nor going down.
    suspend.avi (994.8 KB)

2)The partile mass increase insteal of decreasing with the chemical reaction going on.

frame_000033
frame_000033930Ă—680 25.7 KB

Best Regards!

#2

I found that a few switchs is elusive in this .mfix file：

  1. break_down_solid_inventory_by_phase
  2. ew_young_actual & vw_poisson_actual

I know what is ew_young, which is explained in the dem-doc (R. Garg, J. G., T. Li, and S. Pannala (2012). Documentation of open-source MFIX–DEM software for gas-solids flows.). But what does it mean by “actual”? The user-guide gives an short description, “Used for computing correction terms for DEM conduction”, which makes me more confusing.

#3

There are still quite a lot of the parameters and UDFs are not well defined and should be fixed,

  1. The reaction heat of the water gas shift reaction CO+H2O–> CO2+H2 is 41 KJ/mol, so it should be 41,000,000 J/Kmol.
  2. For this reaction, in the UDF, it write as:
    RATES(Rg_CO) = 0.029 * exp( 3.40d7/(8314*T_g(IJK) ) )
    so this means even though there is no CO and H2O in the reactor, it will still react.
1 Like
#4

Thanks you very much for the recommendations!