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how to add heat flux boundary condition

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Old   January 29, 2015, 23:12
Default how to add heat flux boundary condition
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JISHNU H
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Dear FOAMERS,
Please tell me how to add heat flux boundary condition. I had proceed with settingFixedGradient keyword in temperature file. But it shows some error
keyword gradient is undefined in dictionary. I know this is a stupid question. mBut please help[ me
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Old   October 27, 2015, 19:25
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nasir musa yakubu
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Hello,

Likewise, i have the same issue, i would want to know how to add heat flux with respect to a particular direction i.e x, y or z.

please help.

thanks
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Old   October 28, 2015, 03:38
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Hello guys,

can you explain in more detail what you have done so far and maybe post relevant input files and the error message? Also it would be easier to help if you tell us what information you've gathered so far.

Best regards,

Kate
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Old   October 28, 2015, 07:30
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nasir musa yakubu
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Hello,

with regards to my case, i don't have a solid heater heating up the geometries per say. what i want to use is a non uniform heat flux boundary condition (result from monte carlo solar ray tracing), in table, grid, and or array format (100x 100 elements) representing the concentrated heat flux on a circle with 3cm radius propagating along one direction to heat up the wall and fluid regions and between the walls and fluid regions, there would be heat transfer interms of radiation, convection and conduction. this will be carried out in order to calculate the exit gas temperature. so i am wondering how to go about adding the heat flux. i have already built pretty much the whole case (c, constant and system), and was able to mesh my cad successfully using snappyhexmesh. however adding the heat flux seems to be the mystery, i have been told to look at toposet, which i will do right now, but if you can shed some light on this, it would be grateful. just to give you a better, pic of what i am building, please find attached picture of my case and the flux profile to be defined as a heat flux boundary condition. however, the heat flux can be exported in grid, matrix and table format from mathematica.

thanks
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Old   October 29, 2015, 03:05
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Hi,

the quick answer is I don't know. Nethertheless I want to give you a reply and hope somebody else can help you. I think for defining your circle, you can use topoSet or define it as a separate patch from the start.
Applying a non uniform boundary condition is another topic. Maybe this thread can help you since a similiar problem is discussed there (http://www.cfd-online.com/Forums/ope...onditions.html).
I'm interested in this topic and will try to help if I can. Hope you keep us updatet!

Best regards,

Kate

ps.: How did you make your first picture?
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Old   October 29, 2015, 04:41
Default groovyBc (swak4Foam) or coded boundary condition
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I'd use groovyBc (swak4Foam) for that.
You can give a matrix in form of an extra file, giving the heat flux in each point, and calculate the necessary gradient for the temperature/enthalpy field.
Another possibility is a coded boundary condition.

A constant heat flux an be applied with externalWallHeatFluxTemperature boundary condition.

Code:
    Cube
    {
        type            externalWallHeatFluxTemperature;
        kappa           fluidThermo;
        q               uniform 10689.6552;
        kappaName       none;
    }
Cheers

Fabian
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Old   October 29, 2015, 19:24
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nasir musa yakubu
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Hello,

Thanks for your prompt reply, i really appreciate it, i will look into the methods mentioned and especially the groovyBc (swak4Foam). with regards to the first picture:
i took a screen shot of a folder on ubuntu and used keynote to put it together, using text boxes and and empty shapes to two write the file names and boundaries respectively. However, i was able to export it to power point, and still play around with with, but i would recommend keynote because you can put something like this together in 5 mins.

I ve started reading on swak4FOAM and planning to install it now, however, am wondering if i would still need to create another 3cm radius circular patch on the surface of the lens to represent my concentrated heat flux or would i be able to specify my parameters with groovyBc?

thanks
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Old   November 3, 2015, 03:32
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I'd give it a try. GroovyBC has lots of groovy features
Otherwise you could split your circle into the inner and outer part.
However, I'd say it is not necessary.

Cheers

Fabian
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Old   April 7, 2016, 12:13
Default tower solar cavity receiver
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Gabes
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Hello , thank you for this volunteer effort in order to facilitate our work ,
i'm mechanical engineering student working on my graduation project and i have to simulate a tower cavity receiver with CFD in order to determine radiative and convective losses and effeciency . so i will be very grateful if you help me how to simulate this non uniform distribution solar flux from the heliostats field and integrate it in the CFD geometry as boundary condition , can you help please ..
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Old   April 7, 2016, 15:50
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nasir musa yakubu
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Hello Grandup,

Its good to see someone working on a similar field, i have actually gone quite far with mine ( solar volumetric receiver) with the help of Bruno santos who's been guiding me over many many months in different pages within the forum . first of all, i can see you want to use a non-uniform concentrated heat flux to design a more realistic scenario. this means your project is split into 2 task, generating the non-uniform heat flux using Monte carlo ray tracing technique (MCRT) and running the CFD analysis (couple with MCRT). first of all i would start with two things at the same time if i were you, thats if you haven't done that already. and how long do you have to do this project?

1) develop the Monte carlo ray tracing model and generate results for your heat flux using an open source tool called tonatiuh:

https://github.com/iat-cener/tonatiuh

here you will find all the tutorials and there is one for heliostats i believe.

https://github.com/iat-cener/tonatiuh/wiki/Tutorials

+

they now have an in-built tool for analysing you heat flux and exporting. hence, you use the exported results to serve as your heat flux on open foam. however, i used mathematica to post process my results, as i did mine before the new heat flux analysis feature was added.

2) start designding your CAD for CFD. and make sure you are actually designing you CAD for CFD if not you will be having some interesting problems to resolve.

start learning how to use chtMultiRegionFoam or chtMultiRegionSimpleFoam solvers.

goodluck and let me know how it goes.

regards
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Old   April 7, 2016, 16:51
Smile tower solar cavity receiver
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Gabes
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Thank you very much Esujby , That's exactly what i mean

☻ I already designed my geometry with CATIA and integrate it in CFD .

☻ i have 1 month to do this project .

☻ i'll check this links and the solver and learn how to do the operation .

☻ I'll let you know how things go .
Thank you very much
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Old   April 11, 2016, 13:39
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Hello , i already simulated the flux distribution with monte carlo ray tracing software using NOTATIUH and the output is ASCII file format . so now i will be very grateful if you tell HOW integrate this file in my CFD geometry as a bounday condition . Thanks
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Old   April 11, 2016, 17:10
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Hello Gabes,

excellent, great job, well i if my post processing on mathematica and generated my results as a table file rather than ascii format. but once u generate your results in the form of a table file, you can use this input to define your heat flux. however have you designed you CAD, meshed it and imported it into openFOAM?

anyways you can define your heat flux boundary condition using any of the following inputs, thats the next phase of my project. however i am stuck with fixing my mesh, so i haven't deeply looked into that yet.

http://www.openfoam.org/version2.1.0...conditions.php

i will be interested in seeing your solution if you are able to put it together. as i still haven't completely fired it out myself

kind regards

Nas

Last edited by esujby; April 11, 2016 at 18:48.
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Old   April 16, 2016, 09:34
Default Cavity receiver
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Hello , esujby i generated my data as a table file . csv through an application in tonatiuh forum ( in 5 min haha ) . now i'm working only on panels and uniform flux without cavity in order to test the mesh and models . And i think it goes well with me after running some solutions . now i will bring the cavity and continue ...
in order to determine convective and radatin losses , efficiency .
so i should integrate the .csv file into CFD i think via user defined profile ...

propositions please ?
.csv file with 10000 rows ..
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Old   April 18, 2016, 17:15
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nasir musa yakubu
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Hello Grandup,

i don't know if you are not he right forum lollz....as you seem to be doing your project on Ansys not openFOAM, this is an OpenFOAM forum. yes i don't remember exactly if the user defined profile feature on ANSYS will work with the data file you have, i remember that not been a feasible option but i am not too sure, you should definitely do some research on this. but i don't know if your question is of any relevance now as you are working on ANSYS not OpenFOAM. lastly my university uses ANSYS and i remember asking all the professors and experienced lecturers using ANSYS, they told me they didn't know how to go about adding the non-uniform heat flux. so it will be interesting if you find a way to do it. i am be interested in seeing your results if you find a way. however if you switch to openFOAM i guess i can answer most of your questions.

kind regards

nas
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Old   April 10, 2017, 19:54
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Hello esujby,
Please can you help me in finding the thermalboundary condition, non-uniform solar heat flux distribution around the absorber tube in parabolic solar concentrato using soltrace (If you have any tutorial about using soltrace in PTC ) , and how can I use the result of soltrace to set as Boundary Condition in Ansys cfx.
I have a problem in the compatibility of coordinates between soltrace and Ansys workbench.
If the problem is not clear enough, please let me know.
Best regards,
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Old   April 11, 2017, 09:50
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nasir musa yakubu
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Hello Abdullah,

I wouldn't use soltrace, because last time I checked, there isn't any support for it as it is discontinued. i would use tonatiuh instead. with regards to what boundary to use, will depend on the MCRT output and the exact type of boundary you are trying create, is it a parabolic trough or parabolic dish? and what is the nature of the absorber tube? transparent or opaque.....i will start with the MCRT first before proceeding.

Kind regards
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Old   April 12, 2017, 09:20
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Hello esujby,
Thanks very much for your immediate reply,i really grateful for you, actually, i've a results from soltrace, but i think its not correct because problems in coordinates (attachments).
Present, yes i would to use tonatiuh instead of soltrace, i've downloaded tonatiuh.
I already designed my geometry with Solidworks and imported it to ANSYS.
Please, before the MCRT, have you any tutorial about using tonatiuh in Parabolic Trough Collector to find the non-uniform solar heat flux distribution around the absorber tube, and what about the coordinates.
The absorber is a commercial evacuated double glass tube fitted with the aluminum helical screw tape.

All the best to you,
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Old   April 13, 2017, 10:30
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hello, i need some help about to use BC Profile Heat Flux , who can help me ,
about Soltrace i have some document and articale about it
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Old   April 13, 2017, 17:13
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Hello Mawloud, will you use the BC in Ansys cfx?
about the tutorial of soltrace, please can you share it?

kind regards,
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