Airflow suggestion for Antec 1200 needed.

[eylee86]

Hi I have a new setup going at the moment.

I have an antec 1200 case but I want to switch out the fans. I'm not a big fan of LED lights and I want to use the 3pin motherboard fan connection instead of running 4pin molex everywhere.

I am trying to get the negative pressure going for the case. From researching I thought of doing...

1 top exhaust fan = 1 x 200mm Antec Fan(comes with the case) 137CFM
2 back exhaust fans = 2 x scythe 120mm slipstream 68.54CFM

Total exhaust = ~271CFM out

I have space for three 120mm front intake fan spaces, anyone have any experience with GELIC solutions fans? I'm about to purchase 3 of these for the front:

http://www.newegg.com/Product/Product.aspx?Item=N82E16835426015

they are advertised as 58CFM each which totals 174CFM for the intake, resulting the negative pressured airflow with roughly 100CFM difference.

So here are some of my questions: Is there kind of like a golden rule/ratio of exhaust:intake for the negative pressured airflow? If so what do you guys recommend. I thought 100CFM might be little too big of a difference.

Also If you guys think this GELID solutions fan is going to be a failure, what do you guys suggest? I thought it would look nice with the black case, if the white fans are spinning inside. I wouldn't mind other color combination, black/red maybe. But I do kinda wanna see the fans spinning inside so that I can tell from outside that the front fans are working.

Any other comments are welcome and thanks in advance

 

[JackNaylorPE]

There's a lot of misconceptions about fan flow. For one, fans specs as presented are "open air" with no resistance. Once put in something, they are affected by friction and resistance. So in your example, you have 271 cfm coming out and , you assume, only 174 cfm coming in. Now of that was the case your case would collapse. If it was switched, your case would explode.

What will really happen is something like this. The fans blowing out produce a negative pressure which means that the intake fans are working at less load then in air. So instead of 174, they will probably pull in about 220 ..... similarly, the extra load on the exhaust fans will derate them and knock them down to about 225. About 5 cfm will get pulled in through the various grilles and cracks that don't have fans.

In reverse, with say 271 blowing in, and 174 blowing out, you will find the intake fan cfm dropping down to about 225 and the exhaust bumping up to about 220 w/ about 5 cfm running outta nooks and crannies. In a well designed case, with plenty of air flow, very little air escapes either way thru these nooks and crannies.

Test this for yaself w/ a stick of incense. As the smoke rises off it, place it in front of an opening and see how it draws or blows. It's almost "hard" to create a situation where it will have great effect. Don't get too hung up on the negative pressure issue as dist will freely enter you system thru the intake fan openings....even w/ a filter. If the filter truly filtered out all the dust, you';d be cleaning it more than once a week.