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Mechanical Ventilation of Substation

66 Views, 5 Replies
03/08/2018 5:45 AM

Hi All,

I am looking for help here, i have designed simulation for 20KW heat rejection of transformer by mechanical ventilation of 4500L/s, but i am not able to get the solution properly. 

This CFD solution of substation has already been done previously by some consultant. I am trying to get the same solution by Autodesk CFD. 

have treid multiple times, looked through AEC tutorials and followed exactly.

 

Can anybody please have a look, attached files

i am getting an intake from duct at higher level in the room from 06 supply grilles each 750L/s and exhausting via a louvred door i to the opposite direction.

The purpose is to maintain 5 degree temperature max differential in the room from outside temperature. It means i am taking supply at 30 degree Celsius but i have to satisfy the temperature within occupied zone of 2.2m of room shouldn't be more than 35 degree Celsius

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Message 1 of 5 ( Views: 66 )

Re: Mechanical Ventilation of Substation

03/13/2018 5:45 PM

Hi @uberkuba,

 

Thanks for reaching out to us on the forums. The cfdst files are just pointer files that have no data in them. If you want to share your project then attach a .cfz file. This shouldn't be too hard of an analysis. The boundary conditions should be something along the lines of the following:

 

Inlet: flow rate, temperature

outlet: 0 pressure gage

 

Total heat generation (Watts) on the volume which is being heated. Based on mdot*Cp*deltaT, what is the expected temperature rise?

 

Thanks,



Matt Bemis

Technical Support Specialist


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Message 2 of 5 ( Views: 41 )

Re: Mechanical Ventilation of Substation

03/14/2018 5:13 AM

Hi Matt,

Thank you so much for reply, i am attaching herewith two models. 

 

In the first one i have applied boundary condition to grilles surfaces with flow rate of 750L/s each and temp 30 Degree and outlet is opposite wall/louvre with boundary condition of Pa=0, Central equipment is giving 20KW heat emission.( not getting any result).

 

For second attempt, i have protuded supply duct out of the room and gave 4500L/s flow rate with temp 30 Degree Celsius boundary condition ( this is not giving me the distribution of equal flow rates through each grille , i have got 06, 03 bottom mounted and 03 side mounted). Outlet is hollow wall opposite side and i have protuded that as well ( would this give me the exact result as if have used louvred door? ). I am getting results for this simulation. But dont know whether these should be applied to real conditions.

 

Please let me know, what am i doing wrong?

 

Regards. 

ATTACHMENTS:
CFD Design.zip

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Message 3 of 5 ( Views: 38 )

Re: Mechanical Ventilation of Substation

03/14/2018 5:13 AM

Hi Matt,

Thank you so much for reply, i am attaching herewith two models. 

 

In the first one i have applied boundary condition to grilles surfaces with flow rate of 750L/s each and temp 30 Degree and outlet is opposite wall/louvre with boundary condition of Pa=0, Central equipment is giving 20KW heat emission.( not getting any result).

 

For second attempt, i have protuded supply duct out of the room and gave 4500L/s flow rate with temp 30 Degree Celsius boundary condition ( this is not giving me the distribution of equal flow rates through each grille , i have got 06, 03 bottom mounted and 03 side mounted). Outlet is hollow wall opposite side and i have protuded that as well ( would this give me the exact result as if have used louvred door? ). I am getting results for this simulation. But dont know whether these should be applied to real conditions.

 

Please let me know, what am i doing wrong?

 

ATTACHMENTS:
abcdnew.zip

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Message 4 of 5 ( Views: 37 )

Re: Mechanical Ventilation of Substation

03/16/2018 7:02 PM

Hi @uberkuba,

 

I had a look at your model and everything looks good to me! Your boundary conditions and model setup seems good to me. Doing a quick hand calc I would expect the exhaust temperature to be about 3.25 C higher than the inlet. Using a plane and bulk calculator on the outlet, we are very close to this, which is good.

 

You mention that your design criteria is to have the room be less than 35 degrees. I used an isovolume to show where the temperature is above this.

temperature.png

 

I noticed you had auto forced convection turned on. This will ignore the effects of natural convection. Looking at the velocities in your sim, I suggest turning this off and rerunning. You already have air set to variable which is correct.

 

Thanks,

 



Matt Bemis

Technical Support Specialist


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