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Convective vs Conductive vs Total Heat flux - Plotting

Posted Nov 9, 2018, 6:38 a.m. EST Heat Transfer & Phase Change, Heat Transfer Version 5.3a 2 Replies

Alissa Kamilova
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Hello, I have a 2D axisymmetric domain, where I have imposed a convective heat flux on the wall. This convective heat flux depends on T_ext_ which is a function of the axial position (so it increases linearly as we move down the domain).

Once I run the project, I get the results that I expected. The temperature inside the domain is sometimes hotter and sometimes colder than the external temperature T_ext_. I want to plot a quiver/arrows plot that will show:

-arrows going towards the outside of the wall, in the regions where the wall is colder than the domain,

-arrows going towards inside of the domain, in the regions where the wall is hotter than the domain

However, no matter how I plot the arrows (convective heat flux, conductive heat flux, total heat flux), I can't get them to do that, even though the temperature profile does show that there are both such regions.

I went through the documentation, and the names of the fluxes don't exactly match the variable names that I have, because I am plotting ht.cfluxr and ht.cfluxz (and ht.dfluxr, htdfluxz for conductive), but the documentation says I should plot ht.ccfluxr and ht.ccfluxz to get the flux out of the boundary which is what I want. However whenever I input this it does not recognise the variable name.

2 Replies Last Post Nov 9, 2018, 9:56 a.m. EST
Nicolas Huc COMSOL Employee

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Posted: 6 years ago Nov 9, 2018, 8:40 a.m. EST

Hi Alissa,

Thanks for you report. I just tried to reproduce the problem. Using the default arrow plot (conductive heat flux) in the domain I got the kind of plot you were expecting. Moreover I could not find the part of the documentation that mentions "ht.ccfluxr".

Could you send us your model through the support so that we can investigate ? Also the precise reference of the documentation page or a screenshot showing it would help.

Best regards,

Nicolas, Heat Transfer group

Hi Alissa, Thanks for you report. I just tried to reproduce the problem. Using the default arrow plot (conductive heat flux) in the domain I got the kind of plot you were expecting. Moreover I could not find the part of the documentation that mentions "ht.ccfluxr". Could you send us your model through the support so that we can investigate ? Also the precise reference of the documentation page or a screenshot showing it would help. Best regards, Nicolas, Heat Transfer group
Alissa Kamilova
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Posted: 6 years ago Nov 9, 2018, 9:56 a.m. EST

Hi Nicolas, Thank you for your quick response.

I cannot send the model as it has sensitive data. The documentation page is 714, Chapter 13: The heat transfer branch. There is a table (Table 13-1 Heat flux variables) and the heat flux I am refering to is called convective out-of-plane heat flux, denoted by variables ccflux_u, ccflux_d, ccflux_z. (And I imagine the last letter would change depending on which coordinate we are referring to).

I still cannot get a situation where the heat flux is coming out of the wall, in regions where the domain is hotter and T_ext is colder.

I am using a heat transfer model coupled with a creeping flow model, I don't know if that makes a difference in the domain definitions.

Best regards, Alissa

Hi Nicolas, Thank you for your quick response. I cannot send the model as it has sensitive data. The documentation page is 714, Chapter 13: The heat transfer branch. There is a table (Table 13-1 Heat flux variables) and the heat flux I am refering to is called convective out-of-plane heat flux, denoted by variables ccflux_u, ccflux_d, ccflux_z. (And I imagine the last letter would change depending on which coordinate we are referring to). I still cannot get a situation where the heat flux is coming out of the wall, in regions where the domain is hotter and T_ext is colder. I am using a heat transfer model coupled with a creeping flow model, I don't know if that makes a difference in the domain definitions. Best regards, Alissa

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