Fan +/- pressure and cfm relate question

[SparkleDJackson]

Goodafternoon bros and broettes. I have been thinking about exhaust solutions for the past few days which has got me thinking in general about my fans. So my system will have 12 Fans pushing air into the case in a push pull config on two 360 v2 gchangers. Afaik push pull does double the amount of cfm it only increases static pressure so then really i have 6 intakes. I think my fans are about 60cfm @1500rpm so 6x60=360cfm entering my case a minute so for exhaust do i need to push more cfm out than that which enters. Im not sure of the theory behind in because say for example i only exhaust 100cfm does that mean i have an excess 260cfm worth of warmed air trapped in the case reducing the effectiveness of my intake charge??? So then should i be aiming for a pressure neutral config where im sucking in and pushing out roughly the same volume of air so if i was able to get for example 4 140mm fans the push about 90cfm to give 360cfm of exhaust. Would this be ideal or is it better to have some sort of pressure in the system. Has anyone thought of this before or experimented? Anythought would be cool

Peace

 

[Firat]

Im having a similar dilemma but I read somewhere (can't find source) and the majority said it best to have ~ + 20CFM positive air pressure that way you will not get dust coming into your case as well as not having too many hot spots

 

[S_I_N]

no it doesnt really double the cfm of the fan what it does is helps the push fan by pulling the air while its being pushed. I would say it'd keep the rated 60cfm instead of it getting knocked down by the fins. Plus the cfm rating is contingent on it being at 12volts (or whatever voltage rating for the 60cfm point) in most cases you will not be running your fans full tilt. 60cfm rating is considering a clear unobstructed air intake/exhaust path. When placed on a rad its knocked down a bit. When behind or in front of an air filter again it looses a little umph. Now were not talking major umph loss but it can add up. Take a fan and run it full tilt and feel the air flow then put it in blowing thru a rad and you'll see what I mean. In most cases over thinking airflow can lead to frustration.

 

[BKCXb]

Like SIN said don't think about it too much...if it bothers you play around with it a bit.. alot of things that make sense in your head doesn't pan out in real life.

The way I go about it is I turn off every fan that is not 100% needed. I run the system a while and take different temps in different parts of the case. I record any warm spots, which indicates a dead space or not enough CFMs in that area. I turn on the fan closest to that area as low as it will run, and see what change that makes. If no change is made I run the new fan faster or try turning it around.

When I get the best cooling from that fan I add in others one at a time, rechecking how it relates to the others.

Every so often like now, when it gets alot hotter I gotta ramp up a few fans to get the same cooling. but I'm always looking for the best cooling with the least fans(or fan noise)

Give it a try and let us know what you find out.