PC hardware: Reversing heatsink fan airflow.
Cooling considerations
by murrays - 7/10/09 8:19 PM In reply to: Reversing heatsink fan airflow. by GueritoI have never seen anywhere where the power supply fan is considered part of the total cooling picture, but it is. That fan pulls air out of the top of the case. Case fans often are installed to both pull and push. When you think about it, blowing air into the case assists the power supply fan by pressurizing the case. Fans which blow out of the case work against the power supply fan by de-pressurizing the case, and if they are controlled by MB temp, they probably come on when the PS starts needing extra cooling because everything is working harder. So it makes sense to arrange the fans to blow outside air into the case (it'll be cooler than the air in the case) at all times. Most cases are nowhere near airtight anyway, so a lot of air will be simply vented as well. As for hot air rises, it does in still air, but it takes very little breeze to de-stratify warm/cool air, so as long as fans are running, forget about convective cooling. I have 2 case fans, both MB controlled, one is relocated on the side panel to blow on the video card when it's working hard and the other is on the back panel and blows toward the CPU. Even when they are not running, the PS fan is pulling air through the fan openings to where it is needed. Use your own head and think things through.
Push, pull, suck and blow.
by Guerito - 7/10/09 8:50 PM In reply to: Cooling considerations by murraysThere's never gonna be an ideal air cooled system, whichever way you look at it as long as air is circulating (even round and round in a circle) it's cooler like running water doesn't freeze as easily as still water (remember physics lessons at school). The best solution is liquid cooling but sorry to say expensive. If you really want to see how the air in your case is moved around, take off the side panel and hold a lit cigarette inside and watch where the smoke goes or use some kind of smoking device. Or the extremem, EXTREME solution is submerge the whole case in light oil like the oil used to cook with(have you seen the video where this is done?) oil doesn't conduct electricity so all components work fine without any fans and its noise free but maybe a little messy.
Looking at the case linked below...are you saying the
by VAPCMD - 7/11/09 7:41 AM In reply to: Cooling considerations by murraysfan located at the rear of the case is pushing air into the case versus pulling warm air out ? Is there a case fan at front of case ? Are you using an aftermarket CPU HS Fan ?
http://www.newegg.com/Product/Product.aspx?Item=N82E16811160026
(NOTE: See PIC showing case from rear where you can install two fans)
VAPCMD
Not applicable for me
by Guerito - 7/13/09 5:25 AM In reply to: Cooling considerations by murraysLike I said my case never has the left panel fitted (left as in looking at case from front) so all this pressurized stuff, which I think is nonsense anyway no off-the-shelf case is pressurized, is irrelevant. All I said would it hurt to reverse the cpu fan and it doesn't I've already tried it and there is no difference in heat dissipation, cpu runs at same temp.
No
by DKT27 - 7/11/09 7:25 AM In reply to: Reversing heatsink fan airflow. by GueritoThe processor fan extracts all heat from the processor and removes it out of the cpu so that your cpu doesn't get heated. No need to change it's position. It can cost you a whole cpu to whole computer.
Anyway, what temp bios is showing?
Till 50-60 degree(C). It is okay. If it is beeping in less temp than that, disable the waring beeps in bios.
CPU fans blow toward chip/heatsink
by CrossCrucial - 7/20/09 9:57 AM In reply to: No by DKT27Heatsink fans blow TOWARD the CPU.
The air will of course bounce back off the CPU and to the sides.
Pushing cool air towards something is more efficient at cooling than pulling hot air away.
This is why you are cooler sitting under a running ceiling fan when its blowing on you, rather than it running in reverse (it will pull from the sides rather that directly below it/ you wouldn't feel a thing)
I don't agree with you.
by DKT27 - 7/20/09 11:59 AM In reply to: CPU fans blow toward chip/heatsink by CrossCrucialI have talked to three computer engineers about this subject. They all agreed with me. One of them is a chief in a computer manufacturing company. Sorry but cannot call name of the company or person in public.
Guess that proves that engineers are not always right.
by VAPCMD - 7/20/09 6:21 PM In reply to: I don't agree with you. by DKT27Here's my experience over 20 plus years and initially I thought the same as they did.
If you look at fans mounted on Intel or AMD CPUs....they all blow air downward over the heatsink toward the CPU.
Second where the fan sits on top of the HS and the FAN could be mounted to blow up or down, I've only seen one mfg (ALPHA Cool) out of the many many aftermarkets HS Fans recommend the fan pull air thru the HS upwards. Otherwise they blow air downward toward the HS and CPU
Last, believe if you look at the vast majority of high-end aftermarket HS Fans, you'll find the fans blow toward the heatsink...not away from it.
If you find multiple examples to the contrary ...where the mfgs specifically recommend the fan be mounted so as to pull vs push air through the HS...let me know. Otherwise I'll continue to think as I do now.
If you need heatsink mfg names, try Frostytech.com.
VAPCMD
That another thing.
by DKT27 - 7/21/09 6:37 AM In reply to: Guess that proves that engineers are not always right. by VAPCMDMan I'm talking about normally mounted fan. Not any additional installed fan. My point is that he shouldn't change it's position. The side upward or downward depends on the design of the motherboard. He will damage the processor or whole cpu if he tries to change his fan's position when his motherboard design doesn't allow it.
The only thing we agree on generally is
by VAPCMD - 7/22/09 8:17 PM In reply to: That another thing. by DKT27there's no need or significant benefit to reversing the HS fan airflow in most cases. Think I said that about 10 posts back but who's counting.
And since you brought up opinions of 'experts', someone needed to address the misinformation that as fortune would have it, the original poster tested and proved wrong.
Regarding 'damage the processor or the whole CPU if he tries to change his fan's position when the motherboard doesn't allow it' ....there's not many cases where changing the fan position or direction would damage either the processor or the CPU.. it just isn't a pass - fail, run - not run, difference. No need to cause undo alarm or more confusion here.
VAPCMD
Interesting repair that covers your topic...
by Willy - 7/23/09 8:54 AM In reply to: I don't agree with you. by DKT27I had to repair a HP pavilion 6835 system. Its an older system and it would just shutdown and reboot. Upon inspection, I found the PSU fan was seized. This is a mini-PSU with a fan exposed to the outside of the PSU box but within the system case. This in turn blows directly onto the cpu HSF. I cleaned the HSF as good as new. I had a used PSU to install to replace the old PSU as the caps were also bad, thus I wouldn't trust old PSU. Installed and still the system would repeat failure. I then noticed the PSU fan was reverse of the what the old PSU had as mounted. I then reverse the new PSU fan to be correct. The system now runs well and doesn't falter. I has also refreshed the cpu paste as the thermal tape had dried-up and wasn't as effective.
So, it all depends on how a system is build to handle its "airflow" and just what works in one system won't necessary in another. In this cases the cpu HSF needed the extra cooling provided by the PSU fan. FYI- the old replacement PSU came from an eMachine system.
adios -----Willy 
Nope,
by Dango517 - 7/12/09 6:43 AM In reply to: Reversing heatsink fan airflow. by Gueritonot a good idea. Will most likely create a system error/warning and shut the system down to protect it. Replace the thermal paste first if this fails to improve the problem then get a better CPU cooler.
reversing cpu cooling fan
by carbonspark - 7/13/09 6:53 PM In reply to: Reversing heatsink fan airflow. by GueritoThe fans used in computers are Dc brushless, meaning you can not reverse the power to the fan with out toasting it. What is the temperature of the room? I have seen people trying to run computers in attic lofts and such where the room temp is so high the cooling fans just can't do it.
Apply.
by DKT27 - 7/16/09 5:58 AM In reply to: Reversing heatsink fan airflow. by GueritoYea, applying heatsink or thermal tape in between your fan and processor can reduce your PC temp drastically. It works for me properly.
CPU temp. results for push & pull airflow
by Guerito - 7/21/09 7:26 AM In reply to: Apply. by DKT27I didn't expect such a response to my post so I did some temp. testing.
The cpu is an AMD dual core, 95 watts, running at 2.8ghz (not overclocked). Standard fan supplied with cpu upon purchase.
Motherboard is a Gigabyte MA770-UD3. OS is Windows 7 (which has many less background services running compared to Vista), BIOS is Award Modular BIOS v.6.0. CPU warning temp. is set to lowest 60C/140F. Case side panel is removed, the only other fan in the case is the psu fan. CPU heatsink fan is BLOWING (PUSHING) air down onto heatsink. Thermal paste is used. Room temp. is 17C and cloudy (not cloudy in the room). Program used to report core temps. is 'Core Temp.' I checked the temp at two points.
Core temp. at idle (no apps running, only normal background services) = 36C.
Core temp. when playing game (Dead Space) 48C.
Not a significant heat increase considering the machine is running a demanding game and well within the warning setting.
Turned off machine swapped out fan and heatsink for the reversed airflow fan SUCKING (PULLING) air away/up from the cpu, applied thermal paste same quantity as before. Same test applied.
Core temp. at idle 36C.
Core temp when playing game 50C.
A two degree difference, when gaming, between pushing and pulling airflows.
This was on a mild day. When I recieved warning beeps in the past the room temp. was 26-27C, a big increase. This is what led me to use an external/personal fan to aid in the cooling of the CPU and Northbridge passive heatsink which on this board really has serious overheating issues.
Make of this what you will.
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