heat transfer with small particles

Submitted by nom on Wed, 04/18/2012 - 18:34

Hi

I successful run a simulation of a cold fluid heating up while passing through a packed bed of big (D_p=1cm) hot particles. (similar to your test case "heat transfer in packed bed"). However, if I use small particles (e.g. D_p=200e-6m) the simulations runs without an error but the particle temperature has an unrealistic negative value (e.g. T_p = -4000K).

Does anyone has an idea where the problem could be?

Thanks!

Forums:

Oliver.pasqual | Thu, 04/19/2012 - 03:50

Hi nom,
the same problem occured to me.
basically it's the problem of the timestep, the source term for the scalar transport equation is so large that the value of result overflow. perhaps you can try to construct another case with a small time step.

oliver pasqual

nom | Fri, 04/20/2012 - 17:34

Thanks, that solved my problem.

I have an other question concerning the initial particle temperature. As far as I see, in the "packedBedTemp" example, there are 3 commands connected to the particle temperature in the "in.liggghts_init" file, namely:

#heat transfer
fix heattransfer all heat/gran 600
...
#set particle temperature for the bed
set region total property/atom Temp 600
...
#this one invokes heat transfer calculation...
fix cfd2 all couple/cfd/convection T0 600
...

But even if I change the temperature from 600 to e.g. 300 the particle temperature stays the same (600K). Does anybody know why?

Thanks!

Oliver.pasqual | Mon, 04/23/2012 - 03:12

Hi,
you can have a look at the liggghtscommand file in the constant folder.
and comment out the second 'execute'......
the coupling command tell liggghts to set the temperature of all particles to be 600 in the coupling process.
oliver pasqual

kunzhang's picture

kunzhang | Wed, 05/08/2013 - 20:42

Hi nom,

For this case, do you fingure out what is the commands meaning for:

fix cfd2 all couple/cfd/convection T0 600

what does the T0 and 600 stand for?

Thanks!

Kun

kunzhang