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validation with Ergun equation

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Old   October 5, 2016, 12:13
Default validation with Ergun equation
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mhs
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Hi every body

I have simulated natural gas flow in a filter as a porous media in ANSYS fluent. the results, such as pressure drop, have a good consistent with the real case.
now I want to validate my simulation by comparing pressure drop across filter from ANSYS Fluent, with pressure drop obtaines from Ergun equation:

delta P= (150*viscosity*filter thickness*((1-porosity)^2)*Vs)/((Dp^2)*porosity^3) + (1.75*filter thickness*density*(1-porosity)*Vs^2)/Dp*porosity^3

and Dp is diameter of particles that made the porous media. as I know Vs is volume flow rate/cross section area.
all of parameters in the equation are clear, except Vs.

I put several value for Vs from ANSYS Fluent such as facet average for velocity magnitude, radial velocity, volume flow rate/area and... . but all of them have big difference with Ergun result. I thing the problem is with Vs and need help to find correct Vs in my case.

also my filter is like a tube with close end. flow enter from one end and exit from body of tube that is porous. my flow in turbulence and I have used RANS model for it.

Thanks for your attention
best regards
mhs
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Old   October 6, 2016, 01:45
Default deriving theporous media coefficients based on experimental results
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shreehan Abd El-Ghafour
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dear mhs,
are you sure that Ergun formula is the most appropriate method for your case?
i work in stirling regenerator and i used the experimental formula suggested into the FLUENT user‘s guide under subtitle:
"Deriving the porous coefficients based on experimental pressure and velocity data"
because you have experimental results , this method is the best for you
best regards
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Old   October 7, 2016, 09:53
Default Using the Ergun Equation to Derive Porous Media Inputs for a Packed Bed
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mhs
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dear sh.a.ghafour

first of all, thanks for your responding.

I don`t have the experimental data for V vs P. I just have pressure loss data in real case.

my procedure was like "Using the Ergun Equation to Derive Porous Media Inputs for a Packed Bed" part in fluent user`s guide.
I found alpha & C2 like this part of user`s guide (equation 7.19-17 & 7.19-18 in fluent 6.3 user`s guide ), and then put them into the software. now the results of fluent have a good agreementt with real data. but there is a big difference between Ergun pressure loss and fluent results for this parameter.

I thing the problem is with Vs that I read in false way.

mhs

Last edited by mhs; October 9, 2016 at 03:09.
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Old   October 8, 2016, 12:11
Default Using the Ergun Equation to Derive Porous Media Inputs for a Packed Bed
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mhs
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dear sh.a.ghafour
first of all, thanks for your quick responding.

I did the procedure that is explaned in "Using the Ergun Equation to Derive Porous Media Inputs for a Packed Bed" in fluent user guide. and define my porous media base on that. (use of Ergun eq and darcy - forchheimer eq)

but now, my results have a good agreement with real case and a big difference with ergun delta P.

I think the problem is with my V , and I`ve read it from false place.

Last edited by mhs; October 11, 2016 at 16:27.
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