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More than you cared to know about PC fans

nick-black.com

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Re: More than you cared to know about PC fans

#91

Post by c_o_n_v_e_x »

owenversteeg wrote: post #11

Does anyone know if there are high-heat-resistant PC fans (and at what temperatures normal PC fans will melt)? The only fans I can find that claim to be heat-resistant are the Noctua Industrial PPC series which, aside from not being cheap at $33/piece are "only" heat-resistant up to 140C and the airflow isn't crazy high - subjectively the ones I've got feel like they move substantially less air than a standard diesel…

Why do you need a PC fan with such a high temp rating? You could try looking at fans used in military/aerospace gear like Rotron.

Re: More than you cared to know about PC fans

#92

Post by c_o_n_v_e_x »

michaelt wrote: post #18
owenversteeg wrote: post #11

Does anyone know if there are high-heat-resistant PC fans (and at what temperatures normal PC fans will melt)? The only fans I can find that claim to be heat-resistant are the Noctua Industrial PPC series which, aside from not being cheap at $33/piece are "only" heat-resistant up to 140C and the airflow isn't crazy high - subjectively the ones I've got feel like they move substantially less air than a standard diesel…

Unfortunately many plastics, and the most common types of solder, start softening before you get to 180C. You can get smoke extraction fans and chimney flue fans that will tolerate higher temperatures, but they're generally an all-metal affair costing more than $33. Assuming the 180C is at your system's ventilation output, could you move your fan to the air inlet so it only has do deal with ambient temperature air? T…

Using furnace vernacular, you have forced draft fans which blow air into the furnace or induced draft fans that sucks out the hot flue gas. These fans are typically centrifugal as they develop higher pressure than an axial fan. You need the pressure to overcome the system flow impedance.

Re: More than you cared to know about PC fans

#93

Post by c_o_n_v_e_x »

dankamongmen wrote: post #87
azalemeth wrote: post #3

Honestly this isn't more than I cared to know about PC fans. I've worked extensively with industrial appliances and fans are bloody important and underlooked: fan failure is often the step that precedes component failure. The one part of the spec I wasn't aware of was just how insanely high the maximum current draw is; I'm glad that we've made more efficient, longer-lasting, effectively silent air-movers that can fit…

yeah, if you look at the equations at the bottom, power goes up with the third power in relation to rpm. whippin' and drivin' that much air takes some oomph. connect that fan to any normal motherboard, and you're going to burn out your fan header pretty much immediately (especially since inrush current is probably even higher than the steady state).

For those interested, the equations are also known as fan or pump affinity laws:

https://www.engineeringtoolbox.com/fan-affinity-laws-d_196.h...

Re: More than you cared to know about PC fans

#94

Post by ThePowerOfFuet »

paxswill wrote: post #47
ilyt wrote: post #13

I'm surprised it doesn't mention hysteresis some fans have at low speed. Cheap fans often don't have actual proper speed controller on them which means they might start spinning at say 30% PWM but only stop spinning at 15% PWM. That was probably the thing that surprised me most when I upgraded to nice Noctua, at certain PWM it just started, always, and below that it stopped, always.

Those fans that start at 30% and then allow you to go lower are explicitly allowed by the spec from Intel (linked in the article, sec 3.2 and 3.4).

Allowance in the spec doesn't mean that behaviour is desirable.

Re: More than you cared to know about PC fans

#95

Post by Eisenstein »

dankamongmen wrote: post #88
axiolite wrote: post #34

> "there is no readily-available 24V source from an ATX power supply," This is false. ATX provides both +12V and -12V: * https://pinoutguide.com/Power/atxpower_pinout.shtml Hooking them together would provide 24VDC. On a 350W PSU, I see -12V rated to supply 0.3A, which would allow for 24V fans drawing up to 7.2W of power, if desirable. I don't see any reason to prefer 24V fans, however. The current losses over such s…

huh, i didn't know they could be connected like that! i only knew of the -12V as a source for RS-232. thank you for the tip; i'll investigate this (i assume you're correct, just want to understand it for myself) and update the page. thank you very much!

> huh, i didn't know they could be connected like that!

'Ground' is not necessarily 0V, it is just convenient to use it like that. If 'ground' is 0V then 12V - 0V = 12V, but if you make 'ground' -12V then that is 12V - (-12V) = 24V.

Re: More than you cared to know about PC fans

#96

Post by bayindirh »

dankamongmen wrote: post #90
bayindirh wrote: post #5

Nick Black's personal wiki is a treasure trove. The style is a little terse, but it's a non-issue for me.

thanks; this warmed my little hacker heart!

You're welcome. I'm pretty glad that I found your (not so) small corner on the net, and bookmarked it.

Cheers!

Re: More than you cared to know about PC fans

#97

Post by aliswe »

dankamongmen wrote: post #86

hey neat, i'm glad people enjoyed this (i'm the author)! this was all due to my inaMORAta project, part of my Counterforce project: https://nick-black.com/dankwiki/index.php?title=InaMORAta https://nick-black.com/dankwiki/index.php?title=Counterforce hack on!

nothing on bladeless fans, i am curious if they are useful or useless ... i am guessing a bladeless fan has a bladed fan inside though.

Re: More than you cared to know about PC fans

#99

Post by dankamongmen »

aliswe wrote: post #97
dankamongmen wrote: post #86

hey neat, i'm glad people enjoyed this (i'm the author)! this was all due to my inaMORAta project, part of my Counterforce project: https://nick-black.com/dankwiki/index.php?title=InaMORAta https://nick-black.com/dankwiki/index.php?title=Counterforce hack on!

nothing on bladeless fans, i am curious if they are useful or useless ... i am guessing a bladeless fan has a bladed fan inside though.

i know nothing about them! thanks for bringing them to my attention.

Re: More than you cared to know about PC fans

#100

Post by axiolite »

gnu8 wrote: post #41
axiolite wrote: post #34

> "there is no readily-available 24V source from an ATX power supply," This is false. ATX provides both +12V and -12V: * https://pinoutguide.com/Power/atxpower_pinout.shtml Hooking them together would provide 24VDC. On a 350W PSU, I see -12V rated to supply 0.3A, which would allow for 24V fans drawing up to 7.2W of power, if desirable. I don't see any reason to prefer 24V fans, however. The current losses over such s…

This led me to wonder why we still need the -12V supply - I know the -5V supply was removed a while ago because it was only needed for ISA slots. According to Wikipedia, -12V is for RS-232 ports and PCI slots, both of which are hardly seen on any current motherboards. It should be safe to use it for fans, but 7.2 watts is not very much power. Looking on Mouser, I see 24VDC fans that consume 1 watt or 18 watts dependi…

> one could easily overload the -12V bus

People can easily overload 12V motherboard fan headers, too.

> if they are trying to get a lot of CFM.

If so, they probably have a PSU larger than the entry-level 350W unit I specified. Higher wattage PSUs will provide more power on the -12V rail as well.

> I don’t see a compelling reason to use 24V

Neither does anyone else. Still, correcting a bit of misinformation in the article.

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