Air flow direction when cooling a CPU?

[alm99]

Should the air from the heatsink fan be blowing down towards the CPU or up and away from the CPU?

 

[StrangerGuy]

Every single HSF review I have seen on the Net says blowing down is better.

 

[alm99]

I have an Aspire HSF cooling a athlon barton 2500+. I want to make it as quiet as possible. The HSF uses an 80mm fan and I have a Zalman 80mm fan with the option to have it on noiseless mode. Would it be safe to place it on the noiseless mode and swap the the fans on top of the heatsink?

 

[StrangerGuy]

Originally posted by: alm99
I have an Aspire HSF cooling a athlon barton 2500+. I want to make it as quiet as possible. The HSF uses an 80mm fan and I have a Zalman 80mm fan with the option to have it on noiseless mode. Would it be safe to place it on the noiseless mode and swap the the fans on top of the heatsink?

I don't really know, but you can always test the CPU load temps with the Zalman fan. 🙂

BTW undervolting is a great option to consider it you are running at stock clocks.

 

[furballi]

Use the colder air from the duct or case. This would require blowing air into the CPU cooler/case.

 

[Luckyboy1]

Down

 

[the cobbler]

I'm going against the grain to say up is better.

I flipped the fan on my TT BigTyphoon and load temps on the mosfets and chipset dropped almost 5C, the back of the video card is noticably cooler, and the CPU itself dropped a degree or two on load. Makes sense because it was just pushing hot air down onto the mobo and VGA. Now it exits at the fan, where it is pulled directly out the back of the case.

 

[furballi]

The key variable is the INTAKE air temperature to the CPU cooler. When pulling air from the MB side, the intake air going to the CPU cooler will be HOTTER due to the heat from the surface mount devices on the board. Of course these devices on the board will run cooler, but the cooling capability of the CPU will suffer due to the higher air intake temperature. The efficiency of the cooling fan will also degrade due to the higher air flow resistance on the intake side.

If the case vents well, then the CPU cooling fan should always blow into the case for best cooling performance.

 

[the cobbler]

Originally posted by: furballi
The key variable is the INTAKE air temperature to the CPU cooler. When pulling air from the MB side, the intake air going to the CPU cooler will be HOTTER due to the heat from the surface mount devices on the board. Of course these devices on the board will run cooler, but the cooling capability of the CPU will suffer due to the higher air intake temperature. The efficiency of the cooling fan will also degrade due to the higher air flow resistance on the intake side.

If the case vents well, then the CPU cooling fan should always blow into the case for best cooling performance.

what I found is that because of the way my mobo is laid out, case fan placement, etc. heat from the GPU and chipset were traveling up the (window) side of the case and being drawn into the CPU cooler, and all that hot air was blown down across the mosfets and back of the video card before heading upwards to the outtake fans and PSU fan at the rear of the case. I tried flipping the fans around so the higher rear fans took air in and the lower front fans exhausted air. But the PSU still exhausted out the back and thermodynamics weren't cooperating, wasn't removing heat very effectively I guess partially because of the turbulence?

i really think it would be different for each person depending on the airflow in their case, what kind of memory they're using, etc. definitely would be worth testing in each direction.