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Old   October 16, 2008, 09:20
Default Allan Walsh,I need your help.
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ymg
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hello, can you help me please, I need write a "udf" to simulation the combustion of coal.when i cope with the particle temperature(P_T(p)), I don't know which Macros can be used to describe the radiation temperature or G(the incident radiation) or I(the radiation intensity)? http://cdlab2.fluid.tuwien.ac.at/LEH...ug/node831.htm Surface Combustion (Law 5) (22.9-86)
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Old   October 16, 2008, 13:31
Default Re: Allan Walsh,I need your help.
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Allan Walsh
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From my experience, I could offer two pieces of advice.

First, ask yourself if your really need to write a UDF. Are you concerned right now that the built-in Fluent combustion laws for coal are not suitable for your purpose? Do you have good experimental data for the combustion rate which cannot be approximated with Fluent and you think can be improved with a better combustion model? If so, then you would want to budget several weeks or months to develop, implement, and test your UDF.

If you just want to model the combustion of coal particles, and implement some sort of temperature model, then writing a standalone model would likely be more satisfactory.

On the second point, we have written UDFs for drying, volatiles release, and char combustion for particles of other fuels (hog fuel, MSW, spent liquor) because their combustion is somewhat different than coal. For radiation, we have just written our own equations based on the local gas temperature and emissivity and particle temperature and emissivity. The local radiative flux to the particle only requires a few lines of code.

On doing this, you will see that the radiant flux is quite sensitive to the particle surface emissivity. How good is your experimental data for this? +-50%? If so, how much time do you want to spend refining the other calculations? And, since we are talking absolute temperatures raised to the fourth power, how important will the particle temperature be in determining the heat flux.

If you are using the P1 radiation model, the various radiation parameters like radiation temperature and incident radiation likely are not relevant for the particle heat fluxes. You would have to check this against your own calculations.

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Old   October 16, 2008, 20:55
Default Re: Allan Walsh,I need your help.
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ymg
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Thank you very much, in deed, for your reply. could you send me some generic info about"DPM-Source Code for Standard Vaporization Law or SurfaceCombustion Law". I think if i can look at the vaporization law or surfaceCombustion Law 'black box', i can learn more. Desperately need this to debug my UDF that I have wrote to control the surfaceCombustion particles in DPM. My email:ym.geng@hotmail.com or ym.geng@stu.xjtu.edu.cn I would be glad to recieve reply from you. many thanks,best regards

ymgeng
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Old   October 17, 2008, 09:19
Default Re: Allan Walsh,I need your help.
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ymg
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hi,Allan. I am writing my own surfacecombustion law, and I would like to have the standard laws to use them as a guide. if you knows the link to the standard dpm laws, or has kept them from the old one (or even wrote them to practice and want to share them), could you send me some generic info!

Thanks in advance, ymgeng

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