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Old   March 26, 2001, 01:13
Default fixed bed combustion
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Adi
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Hi, For 3D gasification modeling I am using pdf method for the reaction chemistry. But I find difficulties to get the correct result, such as the distribution temperature in the fixed bed combustor are not comparable with the experimental result. The lower portion in the combustor should have higher temperature compared to the upper portion/zone.

Is there anybody can assist me to solve my problem?

Cheer!
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Old   March 26, 2001, 19:54
Default Re: fixed bed combustion
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Greg Perkins
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What models are you ising and Fluent version? How do you model the solid phase, if at all?

Greg
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Old   March 29, 2001, 01:16
Default Re: fixed bed combustion
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Adi
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Hi, Thanks for the asking. I use Fluent 5.4 Version. The reaction model is pdf method (2 stream non adiabatic method). The flow of biomass particles is modeled using discrete phase model. Injection type: cone with customs laws: Devolatilization (4th law), surface reaction (5th law),inert heating (1st law) and the rest are inactives.

For boundary condition; inlet air-velocity: 2m/s, temperature 1000 K, turbulence int:10, turb. length scale :0.001m.

Are there any information which you still wants to know?

Thank you Adi
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Old   March 29, 2001, 19:27
Default Re: fixed bed combustion
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Greg Perkins
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If you're using the lagrangian method then I assume you are modelling a dilute flow of particles - such as in a pf boiler or entrained flow gasifier.

To me, fixed bed combustion, refers to a dense solid phase which may have a volume fraction of >0.3 in which case the lagrangian treatment is not valid. In this case the solids velocity is very low - almost zero.

Between the too there is fluidised beds where there are strong coupling between the gas and solid phases - and again the loading is such that a lagrangian treatment is generally not valid.

Thanks

Greg

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Old   April 17, 2001, 15:01
Default Re: fixed bed combustion
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Adi
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Hi Greg, So which method will you prefer?

Regards Adi
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Old   April 17, 2001, 20:06
Default Re: fixed bed combustion
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Greg Perkins
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Eulerian models are appropriate for fixed bed combustion but Fluent doesn't have these inbuilt.

Greg
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Old   April 18, 2001, 23:24
Default Re: fixed bed combustion
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Adi
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Dear Greg, Thank you for your reply. So, does it means an UDF shoud be built to support the fix bed combustion?

Cheers Adi
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Old   April 19, 2001, 01:20
Default Re: fixed bed combustion
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Greg Perkins
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Well that's what I'm doing, but its been a major headache to be honest. I wouldn't advise it again, to be honest. Write your own code.

Greg
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