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Old   July 11, 2011, 09:45
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Shriram
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Hello,

I am trying to model a porous medium with transient fluid flow through a circular duct of length 0.4m . The fluid is air at 1000K and 1 m/s and the porous medium is made up of Alumina pellets of dia 5mm. I have selected the alumina as a dispersed solid while air is a continuous fluid.

Porosity setting is at 0.4, I calculated quadratic resistance loss using the equation provided in the help file with a prior knowledge of dp from a rough analytical calculation, I am not sure if this method is the correct approach to find quadratic resistance.

Under fluid models, heat transfer is checked with total energy setting and turbulence is also specified using k-epsilon model.

My prob:

Given the conductivity of alumina as almost 1000 times that of air, I believe the time taken for the thermal wave to propagate through the medium would be at a slow rate say 1mm/s, however my solution seems to indicate a steady temperature distribution with in 2 sec into the simulation.

I would apperciate if anyone could provide some insight on whether this approach is correct or if i have missed something crucial.

Thank you.

Shriram
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Old   July 11, 2011, 19:14
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Glenn Horrocks
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Doesn't this suggest the thermal inertia of the pellets is not being taken into account properly?

Do the pellets move? If not then this could also be modelled single phase with the pallets modelled by a porous medium with heat transfer. This would be a much simpler model and hopefully has all the necessary physics.
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Old   July 11, 2011, 19:14
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Glenn Horrocks
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Doesn't this suggest the thermal inertia of the pellets is not being taken into account properly?

Do the pellets move? If not then this could also be modelled single phase with the pallets modelled by a porous medium with heat transfer. This would be a much simpler model and hopefully has all the necessary physics.
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Old   July 12, 2011, 09:31
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Quote:
Originally Posted by ghorrocks View Post
Doesn't this suggest the thermal inertia of the pellets is not being taken into account properly?

Do the pellets move? If not then this could also be modelled single phase with the pallets modelled by a porous medium with heat transfer. This would be a much simpler model and hopefully has all the necessary physics.
Hi ghorrocks,

Exactly you are correct, the thermal inertia doesn't seem to be taken into account. Do you have any idea how to incorporate it? Also what I learnt from previous posts, the solid phase heat transfer is not accounted in the porous model it seems.

The pellets do not move, they are just randomly arranged.

Thank you.

Shriram
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Old   July 12, 2011, 18:53
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OK, in that case definitely use a single phase model flowing through a porous medium. In V13 I think you can couple the temperature of the porous medium to the flow. I think this is exactly what you are looking for.
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heat transfer, porous media, transient flow

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