QUOTE(kingmax @ Apr 10 2008, 10:02 PM)
Oh ,thanks , but 700 RPM really that low ? as I know even my house ceiling fan spinning 5 times per second already can few the airflow.If 700 means 700 times in one second sure a lot of airflow.
I know computer casing fan is different but I think isn't that much right ?
Really plan to buy a silent fan with cheaper price.
It's 700 RPM which is rotations per
minute. Not per second.
Generally, the larger the fan, the more airflow it will produce given the same RPM compared to a smaller fan. Just imagine the fan blades as being a ladle, and the air being soup. A larger ladle means you'll have to scoop less times to transfer 1 litre of soup compared to a small ladle. That's why for silent or quite setups, people go for larger fans like 120 or 140 mm case fans. Although they may spin at a lower RPM compared to 80 or 90 mm fans, they can generate the same amount of airflow, and logically, if operated at the same rpm, the 120 mm fans will push more air compared to a 90 mm fan.
In example, a 90mm fan may be noisy at 2000 RPM, and quiet at 1200 RPM, but at 1200 RPM, the air-flow is not good. The solution to get satisfactory airflow is to:
a. But a super silent but high airflow 90mm fan, which will probably cost a lot, and they don't really exist anyway, due to limits of physics
b. Change to a 120 mm fan and run it at 1200 RPM for better airflow, but no (or hardly any) increase in noise.
That's just a general example, but generally, that's how it works. ( =
This post has been edited by RahXeph0n: Apr 11 2008, 02:30 AM