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## Simulation CFD

Contributor
Posts: 18
Registered: ‎07-08-2013

# Solar heating anaysis - transient curve selection

343 Views, 6 Replies
08-26-2013 08:57 PM

Hi,

I'm currently conducting a research study into the heat transfer processes in brick walls, using Simuation CFD. I need to use a transient (day and night analysis), however I'm not sure which time curves I need to use, or where I would find them.

Would you have any advice, or directions?

Cheers,

Ron

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*Expert Elite*
Posts: 588
Registered: ‎01-19-2009

# Re: Solar heating anaysis - transient curve selection

08-28-2013 06:59 AM in reply to: c3110765

Hi

When you say time curves..What do you mean?

Transient parameters? Like time step size and time steps to run with save intervals

or day night time and region like in this

Dan

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Contributor
Posts: 18
Registered: ‎07-08-2013

# Re: Solar heating anaysis - transient curve selection

08-28-2013 06:01 PM in reply to: Dan.M

Hey Dan,

Thank you for your time, It is greatly appreciated.

I was actually referring to the time curves applied to a surface when setting a temperature boundary conditions. I have a three dimensional model of a small house (cavity walls, insulating roof panel and glass window through which the "sun" is to heat the interior foundation slab and interior space.

I have also had concerns with the transient conditions specified in the solver, however I've followed the instructions on this autodesk page: http://wikihelp.autodesk.com/Simulation_CFD/enu/2014/Help/0360-Learning360/0400-Simulati400/0434-Sol...,

which leads me to have a step size of 864 seconds, and 100 time steps.

The particular concern I had regarding time step curves, is my uncertainty as to which time curve to select (eg, constant, periodic, etc) under the temperature boundary conditions (see attached image).

Finally, my project is currently not solving completely (it exits unexpectedly upon reaching the "processing inputs" phase, and Im hoping that the concern is improperly specified boundary conditions. If the solver still fails to complete after solving the boundary condition concern, I can only assume that my model, or the mesh is not correctly developed, in which case I will have to learn how to fix my mesh (something i have no idea how to do).

Id really appreciate any help you can offer in these matters.

Kind Regards,

Ron

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*Expert Elite*
Posts: 588
Registered: ‎01-19-2009

# Re: Solar heating anaysis - transient curve selection

08-29-2013 06:11 AM in reply to: c3110765
Hi
Did you do the tutorial?
http://wikihelp.autodesk.com/Simulation_CFD/enu/2014/Help/0083-Tutorial83/0294-Tutorial294

Maybe you should attach the cfz here so more people can help and give advice.
Why not assign temperature as steady state BC? Like in the tutorial.
Learning is also something that takes iterations...
If everything goes fine on your model then play with the functions
Dan
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Contributor
Posts: 18
Registered: ‎07-08-2013

# Re: Solar heating anaysis - transient curve selection

08-29-2013 07:05 AM in reply to: Dan.M

Hi Dan,

I Did follow the tutorial, thanks for your suggestion though. Im happy to attach the files i can (see attached), however the .cfz file is a little over 3500 KB, which will not be submitted over this forum. If I can find a way to post it, I will do so. I will require the use of a transient analysis for my research thesis, however it is good advice that you propose I test out the steady state method to at least see if it works. I've just tested it, however it still wont solve.

I have serious concerns that perhaps the model arrangement, or perhaps the mesh is not correct. I wonder if that can be viewed through the cfz file?

Also, I would be very interested in getting personal one on one assistance (as well as this forum) through autodesk. Can you please advice me on how to go about getting a subscription?

I really appreciate any help you can provide. I do understand that if I can send the .cfz file, it should be a much better process, however its too big to submit to the forum.

Regards,

Ron

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*Expert Elite*
Posts: 588
Registered: ‎01-19-2009

# Re: Solar heating anaysis - transient curve selection

08-29-2013 07:15 AM in reply to: c3110765

Do you know how to save a share file?

Pick the first option, "Support" . try to zip the file maybe it will be smaller.

You can use Dropbox and and put here a public link to your file.

If you are a student then you contact Autodesk in the student site:

http://students.autodesk.com/?nd=download_center

Also you should check with the reseller in your country, some of them give free support to students in thier area

Dan

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Contributor
Posts: 18
Registered: ‎07-08-2013

# Re: Solar heating anaysis - transient curve selection

09-01-2013 07:22 PM in reply to: Dan.M

Hi Dan,

Thank you for your advice...I never considered using a dropbox account for this scenario. Here is the shared folder link https://www.dropbox.com/sh/7sxxlhwogarzmgp/D8baxB0B9s

I've included the support .cfz files, in addition to the revit model that I imported into Simulation CFD.

I have been discussing the model with a number of my associates and collegues, and have developed a few potential theories as to why the model is not solving:

-the time curve used in specifying the temperature boundary conditions (on the exterior of the dome environment and the ground volume are not specified correctly. I am currently looking into using a piecewise time curve to simulate real temperatures experienced by the model over time. I hope to have this resolved within the week.

-the glass window situated in the northern wall (through which the heat from the solar simulation is supposed to pass is not set up correctly (can you have a transparent material inside an environment), and have the emmissivity and transmissivity values got to sum to 1?

-the exterior of the environment is not allowing the transmission of solar heat

-the mesh is not correct, particularly in relation to the solid cavity walls in the building, with multiple potential problems found by the mesh diagnosis tool

I would really appreciate any help you could offer in this matter.

Kind Regards,

Ron

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