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Cathar · 03-23-2005, 05:14 PM

Centrif. blowers have a different optimisation point. They also tend to be a lot noisier than axial fans for the same level of air-flow, and they are not exactly things that can be mounted conveniently inside a case.

Keeping in mind that we want sustained air-flow through the radiator that is at least around 43CFM. 43CFM of air-flow has an inherent C/W of 0.04, meaning that a 0.04 C/W is as good as you can get given perfect heat transfer from the radiator into the air flowing through it.

If you take a look around the web, you won't find many blowers that can deliver 43CFM against pressure for low noise, where by "low noise", we're talking about ~20dBA noise levels. If you don find one, chances are it's also a fairly large unit, quite costly, and being run at very low speeds.

Remember, we're also talking about cost here. Hard to compete against a ultra-low-noise, small, compact, and light $5 fan with a large, heavy, noisier $50 blower, even if you can argue that the blower is better for pure performance.

The whole point with making the radiator larger than the 12cm axial fan was to decrease the air-flow resistance to the point that the low-speed low-noise axial fan is operating very high up on its flow curve. i.e. you don't need the pressures provided by a blower to get good performance out of the radiator.

Sure, as Hoot say's, if the radiator is now 16x16cm then let's stick a 15 or 16cm fan on it. Yes - you could do that and get better performance, but what I'm talking about here is extracting the most performance possible for the least effort (on the fan's part) and cost and noise.

To me, it just feel right that I'm matching a super-quiet, $5, 1W powered fan to a radiator designed to work with its specific traits, that provides cooling performance that matches larger/noisier setups. Yes - of course we can stick a larger/noisier fan on it, but then that's moving away from what I perceive to be the primary design goal.

Match the fan/radiator setup with a super-efficient super-quiet 5-10W pump (my other dream - but 15-25W will have to do for now until that day) and we have a setup that kicks anything else in the teeth quite hard in every respect (less power, less noise, low-space, smaller ID tubin, better cooling, moderate cost).

Maybe I should move to Europe.

03-23-2005, 05:14 PM	#157
Cathar Thermophile Join Date: Sep 2002 Location: Melbourne, Australia Posts: 2,538	Centrif. blowers have a different optimisation point. They also tend to be a lot noisier than axial fans for the same level of air-flow, and they are not exactly things that can be mounted conveniently inside a case. Keeping in mind that we want sustained air-flow through the radiator that is at least around 43CFM. 43CFM of air-flow has an inherent C/W of 0.04, meaning that a 0.04 C/W is as good as you can get given perfect heat transfer from the radiator into the air flowing through it. If you take a look around the web, you won't find many blowers that can deliver 43CFM against pressure for low noise, where by "low noise", we're talking about ~20dBA noise levels. If you don find one, chances are it's also a fairly large unit, quite costly, and being run at very low speeds. Remember, we're also talking about cost here. Hard to compete against a ultra-low-noise, small, compact, and light $5 fan with a large, heavy, noisier $50 blower, even if you can argue that the blower is better for pure performance. The whole point with making the radiator larger than the 12cm axial fan was to decrease the air-flow resistance to the point that the low-speed low-noise axial fan is operating very high up on its flow curve. i.e. you don't need the pressures provided by a blower to get good performance out of the radiator. Sure, as Hoot say's, if the radiator is now 16x16cm then let's stick a 15 or 16cm fan on it. Yes - you could do that and get better performance, but what I'm talking about here is extracting the most performance possible for the least effort (on the fan's part) and cost and noise. To me, it just feel right that I'm matching a super-quiet, $5, 1W powered fan to a radiator designed to work with its specific traits, that provides cooling performance that matches larger/noisier setups. Yes - of course we can stick a larger/noisier fan on it, but then that's moving away from what I perceive to be the primary design goal. Match the fan/radiator setup with a super-efficient super-quiet 5-10W pump (my other dream - but 15-25W will have to do for now until that day) and we have a setup that kicks anything else in the teeth quite hard in every respect (less power, less noise, low-space, smaller ID tubin, better cooling, moderate cost). Maybe I should move to Europe.