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Heat and airflow
http://www.silentpcreview.com/forums/viewtopic.php?f=15&t=4691
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Author:  Yomat [ Wed May 14, 2003 9:56 am ]
Post subject:  Heat and airflow

Does anyone have a clue if there is some approximation formula for how to tell how much airflow (cfm) you need to transport a certain ammount of heat (watt)?

I guess it depends alot on a myriad of factors but if we limit ourselfs to removing hot 'air' from a known volume. No heatsinks or anything like that. Just a heat generator that heats the air in a closed compartment with airflow.

Author:  rpc180 [ Wed May 14, 2003 12:01 pm ]
Post subject: 

Here's some mathematics totally over my head.

http://forums.silentpcreview.com/viewtopic.php?t=4442&start=0&postdays=0&postorder=asc&highlight=fan

Author:  powergyoza [ Wed May 14, 2003 12:03 pm ]
Post subject: 

I brought up this issue a few months back in this thread:

http://forums.silentpcreview.com/viewtopic.php?t=2687

Enjoy!

Author:  Yomat [ Thu May 15, 2003 5:23 pm ]
Post subject: 

Thanks guys!

Silly of me not to search the forum properly after such threads. But I thought I was the only one that could spend any time with such things. This forum is my kind of nuthouse. :)

This is what I was looking for (Courtesy of Mirar):

Image

However the long discussion had some points also. I might be able to find out my systems heat dissipation now.

I'm plan a bit to build an enclosure in the future so I need to know how much airflow I need to cool it. Seems like I need some 40cfm to cool 200W. Wich means one beast of a fan. :( .. and that will still give me 10C of temp raise. This means 120mm fans. :P

Now.. might someone have an opinion about underpressure, overpressure or normal pressure in the cabinet? From the formula above (and common sense) you will get lower delta raise in the compartment for the same cfm with underpressure. But then it would also mean that the components inside will be harder to cool which would result in more noise from the case (probably wont matter noise-wise in a the enclosure though). With overpressure you would get better cooling of the components but higher temp in the compartment. With normal pressure you might get the best cooling result but then you will need more fans.

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