Data center simulation in Fluent

kmd · July 15, 2018, 20:17

I am trying to simulate air flow and temperature distribution in fluent. But i am having problems while specifying boundary conditions.
For servers in a rack , i modeled as blocks. air needs flow through servers.

Here is the problem, how to make this as heat source with zone condition and also let air flow.

TomD · July 16, 2018, 04:05

make each server (or a group of servers depending on what you want) a different cell zone.
The best way in my opinion would be:
define a source term for each zone and use them as porous media.
Specify porous terms from each server`s "system curve" (Pressure drop vs. flow rate) to control the flow rate that goes into each zone based on the pressure drop

kmd · October 19, 2018, 12:36

Both should be applied?
about porous term , how to define zone? please explain
Thank you

TomD · October 21, 2018, 05:18

You should apply source term if you want to simulate the heating of the air-for this, you`ll need the thermal impedance of the server
The porous media is used to simulate the resistance of the server to the flow-the flow impedance

Check this for how to define porous media:

https://www.sharcnet.ca/Software/Ans...ous_media.html

kmd · October 21, 2018, 05:30

Thanks for reply, i understood heat source and porous media. Porous media is used to simulate flow impedance. I need a flow of 560 cfm in each server. Since it's surrounded by air zone, i cannot specify
Mass flow. How to set a particular velocity or flow rate?

TomD · October 23, 2018, 10:34

First of all, If you specify the flow rate, you wont "get the airflow distribution" , it would be as you specify it. So make sure that this is actually what you want.
But I guess it really depends on what you are looking for.
I would go the way I wrote two post up, that way the airflow would distribute as it would, taking into account temperature and density distributions.

If you want to specify a specific flow rate, I would still do the same thing, making each rack or server a porous media, and use a pressure jump, such as a fan BC to give the momentum to the flow. you can specify such a pressure jump in a way that you will get the same flow rate for different pressures or vice versa. play with the coefficients until you do. (for example create a constant pressure jump on the entrance of a porous media that gives the flow rate you want on that specific pressure you have defined on the pressure jump BC).
There is probably a another way to do it using a momentum source. But I have no experience with it, so try and read the user manual on that one

October 19, 2018, 12:36	Porous and source term	#3
kmd New Member Dayananda KM Join Date: Apr 2018 Posts: 8 Rep Power: 8	Both should be applied? about porous term , how to define zone? please explain Thank you

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July 16, 2018, 04:05		#2
TomD New Member Tom David Join Date: May 2017 Posts: 17 Rep Power: 9	make each server (or a group of servers depending on what you want) a different cell zone. The best way in my opinion would be: define a source term for each zone and use them as porous media. Specify porous terms from each server`s "system curve" (Pressure drop vs. flow rate) to control the flow rate that goes into each zone based on the pressure drop

October 21, 2018, 05:18		#4
TomD New Member Tom David Join Date: May 2017 Posts: 17 Rep Power: 9	You should apply source term if you want to simulate the heating of the air-for this, you`ll need the thermal impedance of the server The porous media is used to simulate the resistance of the server to the flow-the flow impedance Check this for how to define porous media: https://www.sharcnet.ca/Software/Ans...ous_media.html

October 21, 2018, 05:30		#5
kmd New Member Dayananda KM Join Date: Apr 2018 Posts: 8 Rep Power: 8	Thanks for reply, i understood heat source and porous media. Porous media is used to simulate flow impedance. I need a flow of 560 cfm in each server. Since it's surrounded by air zone, i cannot specify Mass flow. How to set a particular velocity or flow rate?

October 23, 2018, 10:34		#6
TomD New Member Tom David Join Date: May 2017 Posts: 17 Rep Power: 9	First of all, If you specify the flow rate, you wont "get the airflow distribution" , it would be as you specify it. So make sure that this is actually what you want. But I guess it really depends on what you are looking for. I would go the way I wrote two post up, that way the airflow would distribute as it would, taking into account temperature and density distributions. If you want to specify a specific flow rate, I would still do the same thing, making each rack or server a porous media, and use a pressure jump, such as a fan BC to give the momentum to the flow. you can specify such a pressure jump in a way that you will get the same flow rate for different pressures or vice versa. play with the coefficients until you do. (for example create a constant pressure jump on the entrance of a porous media that gives the flow rate you want on that specific pressure you have defined on the pressure jump BC). There is probably a another way to do it using a momentum source. But I have no experience with it, so try and read the user manual on that one