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-   -   Data Center Air conditioning Boundary Condition problem (http://www.cfd-online.com/Forums/openfoam/108748-data-center-air-conditioning-boundary-condition-problem.html)

jaypatel October 31, 2012 13:01

Data Center Air conditioning Boundary Condition problem
 
Hi Foamers,
I am trying to simulate the flow of air in a data center. I am ready with mesh file but now I have a problem with BC.

I have 4 type of BCs.
1 = CRAC(Computer Room Air Conditioner) -> Suction side -> ? (it will be taking air from the fluid domain
2 = CRAC(Computer Room Air Conditioner) -> Discharge side -> velocity(in will be inlet to the fluid domain.
3 = Air inlet to Server Rack -> ?
4 = Air outlet from Server Rack -> ?
3 and 4 must be having same Flow rate as what ever goes in the server due to suction fan in each server comes out from the other side of server.


The flow diagram is like this.

Air enters the the space from discharge side of CRAC(velocity and flow rate are know) the air passes through server (3) ,get heated and exit from other side of server (4), and again this hot air is suck by the CRAC suction side (1)get cooled and supplied again(2)

Thanks for reading.

DineshramBalaji December 10, 2012 08:24

Hi Jay,

I am also working on the same problem. What software are you using and have you decided upon the boundary conditions?

roth December 11, 2012 13:11

Recirc BC
 
I guess what you need is a recirc boundary condition.

Consider swak4foam, and in particular, groovyBC, and even more specifically, the example "average-t-junction":
http://openfoamwiki.net/index.php/Co...age-t-junction

For the air inlet to the server rack, you would specify a negative velocity, everything else outflow-like.

At the air outlet from the server rack, you would code up a groovyBC for temperature that grabs the average temperature in the air inlet (Tavg), add in a suitable rise in temperature:

delta T = Heat (W) / ( density (kg/m3) * Cp (J/kg/K) * volume_flow (m3/s) )

and finally apply this temperature (Tavg + deltaT).

The CRAC units, something similar, but with cooling applied.

Boussinesq solver assumed so that we don't have to worry about density.

Hopefully enough info above to get you started.

DineshramBalaji December 11, 2012 20:47

Roth,

thanks for the info. Will try it and let you know.

Alex Lee July 25, 2013 20:02

Any update
 
Hi guys, interesting topic!
I am wondering have you guys managed to resolve the problem faced?

I am also working on the same topic and would like to team up with you all.

Alex

DineshramBalaji July 25, 2013 20:29

Hi Alex,

Kind of. But there is now a problem in modeling the data center using gmsh.

Alex Lee July 27, 2013 00:26

Meshing
 
I can help you to do the meshing if you can provide us some information.
We have developed a nice GUI for SNHM and OF.

Pls contact me at alexlee@zeb-tech.com and I can provide u with a version for testing.

kedarjan November 13, 2013 01:21

Type of BC's on rack & CRAC inlet and outlet
 
Quote:

Originally Posted by roth (Post 396960)
I guess what you need is a recirc boundary condition.

Consider swak4foam, and in particular, groovyBC, and even more specifically, the example "average-t-junction":
http://openfoamwiki.net/index.php/Co...age-t-junction

For the air inlet to the server rack, you would specify a negative velocity, everything else outflow-like.

At the air outlet from the server rack, you would code up a groovyBC for temperature that grabs the average temperature in the air inlet (Tavg), add in a suitable rise in temperature:

delta T = Heat (W) / ( density (kg/m3) * Cp (J/kg/K) * volume_flow (m3/s) )

and finally apply this temperature (Tavg + deltaT).

The CRAC units, something similar, but with cooling applied.

Boussinesq solver assumed so that we don't have to worry about density.

Hopefully enough info above to get you started.

Hello;

The links are fine and UDF's mentioned are also fine. Can we apply BC's without UDF?

Please reply.
I am working on similar project. I have modeled everything in ICEM-CFD and using Fluent for CFD analysis.

Please reply

Thanks and Regards
SSM

rbaud February 20, 2014 13:12

outflow boundary, fixed velocity, pressure boundary setting??
 
Quote:

Originally Posted by roth (Post 396960)

For the air inlet to the server rack, you would specify a negative velocity, everything else outflow-like.

Hi,

Nice topic, thanks for the interesting tips.

I've tried something really similar to Roth's advises.
But I'm a bit struggling on the boundary condition of what you named the "rack air inlet":
U: negative velocity --> I assumed it means pointing out/leaving the domain
P: ??? outflow-like ?
Traditionally for an outlet a fixed pressure is used, but it doesn't suit there as it will become overspecify with the velocity already set at fixedValue? So I have apply zeroGradient for the pressure (for P_rgh in my case), as I would have specify in case of a fixed velocity pointing inward my domain.
The simulation runs and hits the convergence criteria but I don't think the flow is acting accordingly to nature of a suction area around my "rack inlet"... i.e weird pressure profile and velocity getting a bit crazy close to the "rack inlet".

Any hint or idea on that particular point?? :)

Thanks all,

R


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