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Natural ventilation

26 REPLIES 26
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Message 1 of 27
anasabukhadra
2071 Views, 26 Replies

Natural ventilation

Hello,

 

I am an architecture student, and I am working on a passive cooling, naturally ventilated design. I am still a beginner with Simulation CFD. I was trying to see what my options are with my project. I basically want to simulate how the air enters the room from the outside, how it moves inside and how the temperature changes. I know it sounds pretty simple. Are there any videos or tutorials to help with that? Question 2, does Simulation CFD use weather files or do I always have to specify the weather conditions and so.

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26 REPLIES 26
Message 2 of 27
Jon.Wilde
in reply to: anasabukhadra

Hi,

 

You are going to need to set this up using CFD Boundary Conditions - what is usually contained within weather files?

 

Best bet is to model the building on the ground and also add an air-volume around it - then you can apply flow and temperaure conditions to the inlet and a P=0 at the outlet of the air volume (to let the air escape again).

 

This would be a good starting point I think.

 

Kind regards,

Jon

 

Message 3 of 27
anasabukhadra
in reply to: Jon.Wilde

Thank you for your prompt response. I'll start with this today and I will see where I get and I will ask again if I get stuck with something.

 

Weather files are basically used for energy simulation software such as eQuest. Let's say that for example I want to simulate a building in San Diego, CA. all I have to do is to import the weather file which contains all the climatic data for San Diego through out the year and the software would use it to smulate different  designs, So you wouldn't need to specify any climatic conditions and the software would give you results for the different months/days/hours.

 

Thanks again

Message 4 of 27
Jon.Wilde
in reply to: anasabukhadra

Ah OK, makes sense.

 

Just be sure to start simple - steady state only, no radiation and then go from there once that is working.

 

Feel free to post some images of the setup/results if you need more help.

Message 5 of 27

Hello again,

 

I would appreciate your help answering a few questions. I just need to know if Simulation CFD has the potential of doing what I'm going to show and if you could give me a few tips. 

 

Image number one shows simplified drawings of what I am working on. a small space that is naturally ventilated, with an out door air inlet and outlet. I have a facade system I am working on, which consists of a perforated external skin and a glazed layer behind it.

 

Image number 2 shows how the air is expected to move considering that the top and bottom between the building and the skin are blocked). The air is going to penetrate through the external skin, move down towards the opening to go up again towards the window and leave the space from the outlet).

 

What I need to do is to study the air flow and speed, change in temperature, and thermal comfort inside the space. Would that be possible?  Can you give me some tips please?

 

I would really appreciate your help as I am kind of stuck with this.

 

Thank you!

Message 6 of 27

 
Message 7 of 27
ajay.s
in reply to: anasabukhadra

Dear Architect,

 

Based on your previous post and uploaded images, Yes you can determine "air flow and speed, change in temperature, and thermal comfort inside the space" but as a beginner, you can take this(Solve) as a 3 case:

 

1. Fluid Flow - to know air flow & speed inside occupant space

2.  Fluid Flow + Heat Trasnfer - to additionally find, delta Temperature 

3. Fluid Flow + Heat Transfer + Radiation - additionally, to extract weather conditions, solar loading & to extract thermal comfort.

 

Do, each step exclusively and understand it & proceed further. By completion of all 3 seperate steps you will be confident of using all together & know how simple to use this Tool. 

 

All d best.

 

 

Regards,

Ajay.S

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Message 8 of 27
anasabukhadra
in reply to: ajay.s

Thank you so much for your prompt response. I just want to make sure that the software will be satisfying my needs before I start working on it. I also want to ask one last question before I start; let's say that I have a water medium or moisturised medium on the external skin, would the software also determine the change in temperature after the air penetrates through this moisturised medium?  To simplify the question please look at the image attached with this message.

 

Thank you so much again and your help is much appreciated.

Message 9 of 27
ajay.s
in reply to: anasabukhadra

Dear,

 

These links can be of much help,

 

http://help.autodesk.com/cloudhelp/2014/ENU/SimCFD/files/GUID-599627EC-C556-42DC-9415-BB50BFCBFFC8.h...

 

http://help.autodesk.com/view/SCDSE/2014/ENU/

My suggestion, is to start working with the Tool and explore your requirment, its very simple to use and understand.  

 

All the best.

 

Kind Regards,

Ajay.S

Message 10 of 27

Wonderful. I did play with it a bit and explored a few stuff but just waned to make sure. Thank you so much sir and I ppreciate your efforts.

Message 11 of 27
ajay.s
in reply to: anasabukhadra

Dear,

 

No worries. 

All the best for your projects.

 

Regards,

Ajay.S

 

MICROGENESIS, INDIA

Message 12 of 27
anasabukhadra
in reply to: ajay.s

Hello again,


I finished my design and I'm done with my model as well and want to make
sure I get it right when I import it to Simulation CFD. I'm going to
simulate a room (simple 4 walls and a window), the building envelope has a
building skin that has shading devices and glass layers. I tried importing
the geometry and it gave me so many surfaces on each of the walls. Would it
be better if I import it as surfaces (without thicknesses for the walls and
elements)?

Please let me know so I can start the simulation 🙂


Thank you so much again
Message 13 of 27

OK. I figured this part out.  I am sorry if I am sending a lot. I just want to make sure I'm doing everything right. I have 2 small questions:

 

1-  I have a room of 4 walls, How can I make 3 of these walls adiabatic ( I don't want any heat transfer from the outside or any effects to happen through them).

2-  Let's say that my walls consist of many layers, when assigning the material, does it matter which material I assign to the wall If I enter the film coefficient for the whole wall? Or do I have to import all the wall layers and assign the materials to each one of them?

 

I appreciate your prompt response.

Message 14 of 27
Jon.Wilde
in reply to: anasabukhadra

Hi,

 

1) Unless you have air or a film coeff on the outside of the walls, they will be adiabatic

2) A film coeff is typically used to specify the heat transferred from the solid to the external air. You might be better off creating a material that combines all of the layers into one (much like our PCB calculator), taking the conductivity and thickness of each and using the ratio of that vs the overall thickness to form one material. Might save a bit of time, ensure you have at least 2 elements through any material thickness to properly capture the heat transfer.

 

Kind regards,

Jon

Message 15 of 27
anasabukhadra
in reply to: Jon.Wilde

For point 1, what If I had air outside the walls. I just need the interaction to be with 1 wall, not the others.

for point 2, The case is I have is a typical wall that consists of steel studs, gypsum board, cladding and insulation, I would be importing the wall as 1 layer to the sim software, would it be ok if I assign one material to the wall and specifiy the film coefficient to what is equal to the U value of all the layers?

 

Thak you again.

Message 16 of 27
anasabukhadra
in reply to: ajay.s

Hello,

 

I am really disparate for some help here. I assigned all the materials and the boundary conditions. It keeps telling me I have a problem with the mesh. I made sure the model is done right 100 time and made sure all parts are fine. I tried fining and coarsening many parts with no result. I am trying to attach a copy of the work but it's 12 mb in size.  Whenever I try to preview the mesh the software shutsdown.

 

I am using sim 360 for simulation and it's a pretty small project, a room. I am really disappointed I was counting on the software but it has given me lots of problems.

Tags (2)
Message 17 of 27

These are 2 pictures of it. 

Message 18 of 27
esmaeilk
in reply to: anasabukhadra

Sometimes I get that error when there are small gaps/issues with my design. Try the surface refinement + gap refinement tool in the auto meshing window. Usually does the trick for me.

Message 19 of 27
Jon.Wilde
in reply to: esmaeilk

If that fails, please pm me and I will grab the CFZ file for a quick health check.

Have you already run through the training material?

 

Kind regards,

Jon

Message 20 of 27
anasabukhadra
in reply to: ajay.s

I tried the gap and edge refinement but it doesn't seem to be working. I know I have a lot of 

curvy' forms in the model, I tried to supress them as well but it's not working. The file is almost 10 mb in size and it's not letting me post it here. I would really appreciate any help. 

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