Do CPU HS fans work as well upside down?

[bupkus]

Do CPU HS fans work as well blowing away as towards the mobo?

I have some inexpensive K7 heatsinks with 80mm fans inside a desktop style microATX case and I'm wondering.

 

[Maximilian]

Upside down fan?

 

[bupkus]

Originally posted by: Soviet
Upside down fan?

yep

 

[lsu365]

So you're trying to pull the heat away from the processor? Doesn't seem like it would work too well.

 

[Cooler]

Originally posted by: bupkus

Originally posted by: Soviet
Upside down fan?

yep

Your cpu will die a slow death .

 

[MDE]

You won't know until you try it.

 

[stevty2889]

It really depends, try it both ways. Normaly you want the fan blowing in to the heatsink but sometimes it will work a little better blowing away. It won't hurt anything to try.

 

[AkumaX]

i'd think it would depend what kind of airflow you have

if you look in this picture, it would be more beneficial to have the fan "blowing" into the fins, so it could hit the two towers. Also, cooler air would be coming in instead. If it were "sucking" it would be sucking hot air out, but the fan would have to be strong enough (it's not, because i want it QUIET) to draw out air from behind the 2nd tower in the back

obviously this is a different orientation than what you had in mind, but think about where the direction of airflow in your case would be. do you have an exhaust fan above your cpu fan, and cool air coming from the side? or is there an intake fan on the side of your case, in that case you might want to have cool air from the outside coming from your intake fan to blow on to your HSF.

 

[rivan]

Far from being an expert on the subject, it'd be my thought that it would depend heavily on the heatsink design.

I'd expect airflow to be far less efficient at greater distances from the fan when run backwards like you're suggesting.

 

[AkumaX]

Originally posted by: rivan
Far from being an expert on the subject, it'd be my thought that it would depend heavily on the heatsink design.

I'd expect airflow to be far less efficient at greater distances from the fan when run backwards like you're suggesting.

That's true; anyone remember Alpha's PEP66 and the 'shroud'? That was a "sucking" design.

 

[Markfw]

Originally posted by: stevty2889
It really depends, try it both ways. Normaly you want the fan blowing in to the heatsink but sometimes it will work a little better blowing away. It won't hurt anything to try.

Yes. I agree.

 

[bupkus]

Ok, here goes.

Ok, since I had replaced the 80mm fan that was on this cheapie hsf with a panaflo 80mm(H) and had yet to screw it down, I just ran it blowing upwards and then flipped it over.

Case is a microATX "desktop" design with the lid off.

BIOS readings in celcius blowing away:
System: 25 degrees
CPU: 45 degrees

Blowing towards:
Sys: 28 degrees
CPU: 42 degrees

Oddly, there's a 20 degree difference between the system and cpu temps.
After flipping the fan to flow towards the heat sink the system temp increased...?


Well, it's the cpu temp I'm concerned with so there it is.
BTW, the ambiant temp in the room is about 60 degrees Farenheit.

Conclusion: For this design, the advantage is "traditional" fan/hs usage.

 

[stevty2889]

Originally posted by: bupkus

Oddly, there's a 20 degree difference between the system and cpu temps.
After flipping the fan to flow towards the heat sink the system temp increased...?

The "system temp" is normaly a sensor on the motherboard, so by blowing downward, you are keeping the warmer air closer to the motherboard, that would be why the "system temp" goes up a little.

 

[Zebo]

Better - if you build a 1/2" shroud. Worse direct contact.

 

[sandorski]

It's all about Heatsink design. Most are designed to have air blown down on them, a few to have air blown away from them. Unless specifically stated, fans should blow down on Heatsinks.