Hi all, I originally posted this within the Corsair Air 540 owner's thread, but thought I'd put it in the Air Cooling as a standalone thread to get everyone's opinion.
Here's the content of my question, as was posted over there. I think I'll edit it in the Corsair thread to point here:
Quote:
Here's the content of my question, as was posted over there. I think I'll edit it in the Corsair thread to point here:
Quote:
I'm thinking of using 3 x 120mm fans for the front intake, instead of the two 140mm fans, to increase airflow and have positive pressure in my case.
I wonder, 3 x 120mm fans running at the same speed as 2 140mm fans, does it give more airflow? From my faint physics recollection, and my 30 second google search (literally, just quickly browsed the first physics forum I found), I gather airflow is additive with fans in parallel. So I would have to sum the airflow of the 3 x 120mm fans, and compare to the sum of the airflow of the 2 x 140mm fans. Obviously I would have more airflow per fan if I use faster rpm, and consequently louder fans. But if I want to compare at an approximately equal sound level, I'd be dealing with 3 x smaller airflow vs 2 x higher airflow.
Thoughts anyone?
*edit to add*
So found the following informative article, which explains that when fans are added in parallel, airflow is theoretically multiplied by the number of fans, while in practice the airflow is reduced by outflow turbulence, pressure characteristics, etc:
http://www.ebmpapst-ad.com/media/content/technical_articles/TA_Using-fans-in-series-and-parallel.pdf
Comparing the sound, cooling, and airflow chart for the Corsair AF120 Performance from silentpcreview to that the of AF140 Quiet
(http://www.silentpcreview.com/article1342-page4.html)
(http://www.silentpcreview.com/article1346-page4.html)
Testing methodology:
http://www.silentpcreview.com/Fan_Roundup_6_Scythe_Noiseblocker_Antec_Nexus_Thermalright
If I look at 1,100rpm, silentpcreview's airflow measurements look about the same between the AF140 and the AF120 Performance. The larger fan diameter translates into the smaller thermal rise, I believe (thermal rise is measured on a Thermalright heatsink designed for 170mm fans, so the larger surface area of the fan, the better the thermal performance). So if I take 3 x AF120 Performance, and run them at 1,100rpm, I'd have more airflow than the 2 x 140mm. In addition, total fan area of approx 360mm exceeds the total fan area of 280mm, notwithstanding the fact that the 140mm fan area is partially obstructed by the required shape to support the 120mm fan mountings and sides, while it doesn't look like the 120mm fans would have that problem:
Finally, depending on the fan I use, like the AF120 performance, for example, I would have the advantage of pushing them to 1600rpm, albeit at the cost of louder dBA levels.
Have I completely misunderstood how it works? Hopefully more knowledgeable people can chime in to correct my logic.
Maybe I should start this in a separate thread.