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viscous and internal resistance coefficient in porous media

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Old   March 24, 2009, 03:47
Default viscous and internal resistance coefficient in porous media
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vikas bansal
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please help me what values of viscous resistance coefficient and inertial resistance coefficient should be assigned for an honey combed paad of evaporative cooler.

what are the values of C0 and C1 for power law model
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Old   April 2, 2009, 04:29
Default Viscous and inertial resistance
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To find out the value of viscous and inertial resistance, you can calculated by using the pressure drop coefficient, this is stated in the user guide for porous media.
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Old   April 4, 2009, 02:25
Default modeling of pad type evaporator cooler
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please help me . tell me what models i have to activate for evaporative cooling
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Old   April 5, 2009, 23:23
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Sorry, I didn't use porous media for thermal analysis, so i can't help you on this.
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Old   April 6, 2009, 01:50
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Hi,

You can simulate the evaporative cooling using mixture multiphase model. For this you need to define liquid and vapor phases in the boundary condition panel

with regards,
JSM
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Old   April 9, 2009, 01:51
Default in multiphae mdel how the pad of the evaporative cooler can be modelled as porous med
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in multiphae mdel how the pad of the evaporative cooler can be modelled as porous media because as soon as we enable the multiphase model species transport model get disable in which the inputs for the pad is to be fed.
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Old   April 15, 2009, 10:12
Default value of diameter of water particle
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what will be the value of diameter of water particle to be used in the calculation of viscous and inertial resistance coefficient for modeling of flow through porous media
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Old   April 15, 2009, 11:30
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there are a lot of papers written about flow/heat transfer in porous media that will give you some values for those coefficients. When I did work with porous media I actually did pressure drop measurements through the porous media and was able to calculate those values after curve fitting the data (P v's Velocity) and getting a second order equation for the curve. Fluent hadn't yet incorporated the thermal non-equilibrium model yet.
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Old   October 5, 2010, 10:07
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Hi Andrew,

I'm trying to simulate a packed bed with cocurrent downflow (x direction) mixture of air water. I've used the porous model of Fluent 6.3.

Since I'm concerned about axial flow and do not know the radial velocity, I guess, inertial & viscous resistance are to be defined for each phase only in x direction. (y direction specification won't be required)

How bubble dia for the dispersed phase to be calculated & what drag model needs to be used in "phase panel"?

Currently, i'm using the default dispersed phase dia and "Schiller Naumann" drag law.

I'm facing serious convergence problem and pr drop doesn't match with experimental data.

Can you throw some light on it?

Regards,

SM
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Old   October 5, 2010, 10:09
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It's not water particle dia but the dia of solid/catalyst/packing material (dp) which is used to calculate inertial & viscous resistance.
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Old   October 5, 2010, 10:35
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you have a two-phase flow flowing in the x-direction through a packed bed? I am making sure I understand the problem. And, you are assuming all velocity is in the x-direction? And, the Schiller drag is imposed on the air bubbles or on the particles? I would think that your drag law would be a function of the velocity of whatever it is being imposed on, right? - do you know what the velocity/Re is?
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Old   October 6, 2010, 00:54
Default Convergence problem with multiphase porous media case
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Quote:
Originally Posted by mettler View Post
you have a two-phase flow flowing in the x-direction through a packed bed? I am making sure I understand the problem. And, you are assuming all velocity is in the x-direction? And, the Schiller drag is imposed on the air bubbles or on the particles? I would think that your drag law would be a function of the velocity of whatever it is being imposed on, right? - do you know what the velocity/Re is?
Hi Andrew,

Yes, it's a two phase co-current down flow of air water mixture in the x direction inside a Trickle Bed reactor filled up with glass beads (3 mm dia). Air velocity : 0.22 m/sec, Water vel : 0.002 m/sec.

Model configuration : 2 phase eulearian, laminar, unsteady state
Bed porosity: 0.37, Inertial and Viscous resistance for each phase (gas & liquid) has been calculated by following Ergun equn.

delta P/L = E1*Re/Ga + E2*Re^2/Ga (Re -> Reynolds No, Ga -> Galileo No, E1 & E2 --> 180 & 1.8)

Co-efficient of above equation in form of viscous resistance (1/m2) and inertial resistance (1/m) have been put into "porous" panel of boundary condition of Fluent 6.3 in axial direction only i.e. "x" direction.

Since I considered, air as continuous phase and water as dispersed phase (as normally done in Trickle Bed Reactor), "S&N" drag law expects water particle dia to be entered which I left as default (1e-05 m).

The case face divergence problem frequently. It'd be nice, if you can provide some suggestion on this.
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Old   October 6, 2010, 09:28
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Have you looked for any papers doing something similar to yours? I can't remember exactly what mine were, but it seems your viscous and inertia resistances are high. I think mine were very small - but that might be due to the differences in our set-up. I got my resistances straight from lab data like I mentioned above.
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