How does distance of a ducted fan affect its effectiveness?

mathias · Post by **mathias** » Thu Dec 09, 2004 12:38 pm

After seeing the most recent case review, I'm left wondering if those two fans for the CPU duct would be more effecive if they were closer to the CPU heatsink.

Cause if they're not, that would mean I can just have the the case fan however far I want to, probably even outside. If so, what kind of fans would work well for that? Maybe two to four globe fans, or a 16 to 24 cm AC fan?

Bluefront · Post by **Bluefront** » Thu Dec 09, 2004 5:56 pm

Well there is a "sweet spot" as far as distance between a fan and a heatsink (for the best cooling). Using the Alpha and it's fan mount as a good example.....the best distance seems to be about 1/4". Of course different fans with different sized hubs may cause a variation in this measurement......

Now when you bring the sound factor into play, the further away from the heatsink, the less turbulance noise is generated. So there are several factors to consider.

silvervarg · Post by **silvervarg** » Fri Dec 10, 2004 12:30 am

The distance does matter a little like Bluefront mentioned, but it does not affect it a lot. What matters more is if the duct has bends, if the inside of the duct is smooth, how well the ducts seals in both ends and also if vibrations in the duct itself will enhance the vibration noise from the fan.