How to set the thermal conductivity of particles as a user-defined function

MFiX How to
#1

Dear developers
As we know,thermal conductivity of metal changes with temperature.Thus, I am trying to study the influence of particle thermal conductivity varying with temperature on heat transfer between particles.In my case,DEM model and pure granular flow were choosen.However, There are only two choices could be checked-No conductive heat flux and Musser which seem unsuitable for my purpose.In my opinion,UDF may be a better choice.
So I wanna whether my idea is reasonable and if yes,how to realize it.
I am looking forward to your reply!
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#2

@jeff.dietiker @jmusser
Dear sir！Could you give me some advice？Thank you！

#3

Hi Ziliang

According to the design documents for MFiX, UDF is not available for the TFM model. Here’s the relevant section:

  • Select Thermal Conductivity Model:

    • Input controls

      • Drop down menu to select model option
      • Text box to define user value

    • Inputs disabled when not solving thermal energy equations

    • Inputs disabled for PIC solids model

    • Drop down menu options:

      • No conductive heat flux

        • Selection available for TFM and DEM
        • Disables text box input
        • Sets keyword ks_model(#) to ‘NONE’
        • Sets keyword K_S0(#) to ZERO

      • Constant effective conductivity

        • Selection available for TFM only

        • Sets keyword ks_model(#) to ‘CONST_EFF’

        • Enables text box input

          • A positive value must be provided
          • Sets keyword K_S0(#)

      • Bauer and SchlĂźnder

        • Selection available for TFM only

        • Sets keyword ks_model(#) to ‘BAUER’

        • Enables text box input

          • A positive value must be provided
          • Sets keyword K_S0(#)

      • UDF

        • Selection available for TFM only

        • Sets keyword ks_model(#) to ‘USR’

        • Enables text box input

          • Sets keyword K_S0(#)
          • No input required

      • Musser

        • Selection available for DEM only

        • Sets keyword ks_model(#) to ‘MUSSER’

        • Enables text box input

          • A positive value must be provided
          • Sets keyword K_S0(#)

Note: In DEM, all phases must have the same ks_model value. When changing ks_model for a DEM phase, compare its new value with all other phases. If different, ask the user for confirmation to set all ks_model values to that of the current phase.

This clearly states that setting thermal conductivity via UDF is supported only for TFM model, not DEM. Perhaps you can switch to TFM? I am not sure of the underlying reason for this limitation, others may have more to say on the topic.

#4

Thank you for your detailed answers！Maybe my idea is hard to realize by using MFIX! Let’s waiting for other’s opinions!

#5

The thermal conductivity is only stored for each solids phase, not for each particle. I think you could overwrite the thermal conductivity where it is used. There are only 2 files:

Particle-wall conduction:calc_collision_wall_mod.f
particle-particle conduction: des_thermo_cond_mod.f

Look for k_s0 in the files above, and instead of using it, compute the conductivity as a function of temperature and use this instead (use your own variable).

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