Fan Direction

[Guest]

I know this is a debateable issue, but i need some answers...
Right now, my set up is a HSF blowing air onto the cpu, and a case fan right above it also blowing air onto the cpu. This is giving me a lot of heat problems. My first question is should i change the direction of the fans? My second question is if I buy a new heat sink/fan, should I also change the direction of that fan, or should I leave it as the manufacturer set it?
Also, does fan direction matter on the noise control silverado? Thats the heat sink/fan that i'm planning on buying...I guess i should also ask if I buy the silverado, should I have the case fan (the case fan is directly above the CPU) blowing onto the cpu or exhausting from the case?

ShaidarHaran
OoMachinShinoO@cs.com

 

[Kronos]

Rear case fan exhaust....cpu heatsink fan blowing onto processor. Oh...front mounted intake case fan may be required depending on how well ventilated your case is.

I want to die like my Grandfather...in my sleep...not screaming in terror like his passengers.

 

[funkdog]

Just take a look at some of the numbers on other fan issue forums that have recently taken place. This is probably the most debated topic on the Heatsink Forum.

 

[Crashman]

Since heat rises, fllip you power supply fan to make it exhaust, and leave your front fan as intake. As for the heatsink fan, the manufacturer probably knows what they are doing!

Cast not thine pearls before the swine

 

[funkdog]

"As for the heatsink fan, the manufacturer probably knows what they are doing!"

Not necessarily true Crash, my Alpha Pal-6035 heatsink states that the heatsink fan should pull air from the heatsink, but I achieve lower temps when blowing into the heastink.

 

[Crashman]

Most Manufacturers do blow. I did not want to get into the sick/blow debate, but, well,
1)it's easier to push air that to pull it
2)Fans tend to pull air from the sides
3)Because of 1 and 2, it is easier to reach the base of a deep heatsink by blowing, thus, blowing tends to utilize a larger portion of the fins
4)Although heat rises, because most of us use tower cases, the top of the fan is actually on the side, so the rising heat goes from the heatsink to the top of the case, not back to the fan.
5)Air away from the motherboard tends to be cooler than air near the motherboard, because the electonics (like the chipset) on the motherboard also generate heat.
6)For most case designs, an exhaust fan is mounted closer to the top of the heatsink than the bottom. Air is pulled past the top of the heatsink as it is exhausted from the case. This air tends to be cooler than the air near the motherboard, as it is mixed with cooler intake air from the front of the case. Further, this "top of the heatsink" is actually the side, because of the tower configuration, negating the argument for "heat rising" to it (as pointed out in #4).

Cast not thine pearls before the swine

 

[killall]

consider this, a gas doubles in volume for every 10 degrees C it rises (assuming pressure stays the same which it should) sucking air off the heat sink would be a lot less effective than blowing it on... even when considering the tiny blowback from expansion, arrange the other fans so that air cirulates nicely, also try get some nice round ide cables ( i mage my own air circulating much nicer now )

you do not strengthen teh weak by weakening the strong

 

[Guest]

Well....the thing is, i have sort of a problem. My case fan is directly over the CPU....therefore, if I change that fan to exhaust, like it should be, the HSF and the case fan will cancel each other out...which is even worse than what i have. So....given that, should I change them to exhaust (making the HSF suck air off the CPU) or leave them as they are (making the HSF blow air onto the CPU)?

ShaidarHaran
OoMachinShinoO@cs.com

 

[killall]

one suck one blow, the other suck the other blow, two suck, two blow, try the different combinations, measure the temperatures, the noise (shouldnt change significantly, the noise) see which works best...

you do not strengthen teh weak by weakening the strong

 

[funkdog]

I have found the best results for me are 2 intake fans in the back (directly over the cpu, as you stated), 2 exhaust in the front. And my cpu fan blowing down.

This setup resulted in the best overall cpu temps for my rig. I test all other combinations also.

 

[peteb]

When you say directly over, do you mean at right angles?

I wouldn't worry about the the extraction fan pulling air away from the heatsink intake. the heatsink will benefit from the draw of air inwards from your cool air inlet towards the exhaust, which it why it is done.

You need to create a relative low pressure area at the back of the case to encourage cool air there, so that it is drawn through the heatsink. Then you want to exhaust it. They will not 'cancel each other out'.

-* This Space For Rent *-
email for application details

 

[funkdog]

Pete,

My two fan slots in the rear of the case are split at a right angle by the delta on my cpu heatsink. So as far as right angles the answer is yes.

 

[Guest]

actually, its a rather odd set up.
The rear exhaust fan is parallel to the hsf...which exhausts to the rear by a enclosed channel...the two fans have mebbe an inch or two between when the case is closed....and since i don't yet have a front intake fan, or a new heatsink/fan, i dunno if its a good idea to change them yet...

ShaidarHaran
OoMachinShinoO@cs.com