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surface to volume ratio in non-equilibrium porous model of fluent

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Old   June 14, 2020, 23:52
Default surface to volume ratio in non-equilibrium porous model of fluent
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Hi all,

I am trying to model hydrogen combustion in porous zone with fluent. The temperature of the porous solid and fluid is different. However, I did not use non thermal equilibrium model in fluent. Instead, I used a UDS to solve transport equation of solid temperature and I defined a volume convective heat transfer rate between solid and fluid.

When setting the reaction panel of the fluid panel, I am confused about the surface-to-volume parameter. I think this is a parameter that is used in non thermal equilibrium model of fluent. Because I noticed there is a convective heat transfer rate hv defined in the default non thermal equilibrium model. With this hv and surface-to-volume ratio, fluent solver can calculate volume heat transfer rate.

My question is: since I am using my own non thermal equilibrium model and solid temperature equation are solved by UDS. Therefore, I can leave this surface-to-volume parameters to a random number.

Am I right?

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Weiqiang
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Old   June 15, 2020, 05:43
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The surface density is used to determine surface area available in each cell for the transfer of heat between fluid and solid. If you are not using inbuilt model, then it won't matter. But it won't appear if you do not enable non-equilibrium model. And if you enable it, Fluent will solve thermal energy equation in solid matrix as well. Furthermore, you also need to consider it in your UDS as a source term until and unless you do not want any heat transfer across the solid and the fluid. In the latter case, UDS is also not useful since thermal interaction is the only interaction between the fluid and the solid.
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Old   June 15, 2020, 06:05
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Quote:
Originally Posted by vinerm View Post
The surface density is used to determine surface area available in each cell for the transfer of heat between fluid and solid. If you are not using inbuilt model, then it won't matter. But it won't appear if you do not enable non-equilibrium model. And if you enable it, Fluent will solve thermal energy equation in solid matrix as well. Furthermore, you also need to consider it in your UDS as a source term until and unless you do not want any heat transfer across the solid and the fluid. In the latter case, UDS is also not useful since thermal interaction is the only interaction between the fluid and the solid.
Hi, Vinerm,

I did not enable non equilibrium thermal model. However, surface-to-volume option still emerged. I guess maybe it's because I have gas phase reaction mechanism in fluid.

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Old   June 15, 2020, 06:09
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Then that's only for reaction and should appear under Reaction Tab and not under Porous tab.
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Old   June 15, 2020, 06:13
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Originally Posted by vinerm View Post
Then that's only for reaction and should appear under Reaction Tab and not under Porous tab.
yes, just like you said. however, I am wondering why this happen. Because my mechanism is gas phase mechanism not surface mechanism. I don't need to transform surface reaction rate into volume reaction rate

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Old   June 15, 2020, 06:20
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You can ignore it if you don't have surface reactions.
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Old   June 15, 2020, 06:22
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You can ignore it if you don't have surface reactions.
Hi,

thanks for your patience.
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