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airspirit: Okay, I'm going to break away from any science here: when planning for cooling, NEVER go for exact amounts. If you think you need 79 or so CFM, plan on using around 200 or so.
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I'm doing just that, according to my estimates, I 'need' 72.8 CFM. Keep in mind that all the numbers that went into my heat budget were either MFG specs (pump label) or intentional overestimates (100W/CPU, 2X number of drives, etc) and then included an extra 100W as 'fudge factor'. If I was to be more 'realistic' on my heat budget, it would have been on the order of 160 Watts instead of 414
Then I used the '50% of rated CFM through a rad' figure that BillA and Joe mentioned in their articles. Since I'm going to be using two 120mm fans in parallel, I started looking for high Static Pressure (38mm) fans in the 80-100+ CFM (each) range. Currently, I'm looking at Sanyo-Denki 102.3 CFM fans for $5.00 each @ Electronic Goldmine.
In addition, while I want my case to have SLIGHT positive pressure to keep the dust bunnies out, I'm also putting two additional lower volume 120mm X 25mm fans on the case exhausts. For those I'm looking at a couple of Delta WFB1212M fans, (2.95 ea @ Electronic Goldmine) good for a nominal 72CFM each. Since I'm planning to pretty much seal the case (except for whatever leaks through drives and whatnot) the exhaust fans will be in series with the top intake fan, which in effect makes the two pressures add together.
I would hope I never need to run it this way, since I'm sure the noise would be tremendous, but I'm guessing that if I cranked all the fans to max, I'd be doing serious negative case pressure, and sucking about 100CFM+ through the case, and another 50 through the bottom fan / duct combo.
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Really: you can never have enough. You should be able to get one large blower or something that will provide that airflow in near silence if you look and tune hard enough.
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My plan is to get overkill grade fans, then seriously undervolt them w/ temp sensitive controls. I've had some trouble finding a good temp sensitive controller that I liked. My current plan is to make a hybrid unit of a DigiDoc front end feeding the fans through an NTC thermistor controlled FET power ckt.
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NEVER try to skimp on airflow. There is more producing heat in your system than what you are measuring ... think bridges, mosfets, ram, IC's,
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Agreed, part of why I did such an over estimate.
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Fred the Cockroach, etc ....
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'Fred's not here Man...' He prefers Windows systems... (more bugs!)
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CoolROD: I updated the spreadsheet today to convert temps to farenheit and to post the temperature rise (dT)
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I think I may have missed the link on this one, where is it, and what's the title? - I have a Linux box, but StarOffice opens .xls files pretty well. (albeit slowly - one of our target metrics will be if the girlfriend and I can both open and run SO at the same time)
Gooserider