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sucking vs blowing

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AdvanS13

Member
Joined
Dec 10, 2002
Location
Hillsboro, OR
i was reading someones post stating blowing air onto the heatsink is better in "most cases"

why do most manufacturers set them up to suck out hot air or blow out. and not blow onto? how much of a temp drop will i recieve if its blowing onto the heatsink?

seems like it is working against it blowing onto the heatsink, when heatsinks absorb and release the heat. this would just be pushing it back and also sucking any extra ambient heat wouldn't it?
 
as far as i know, most heatsinks are configured blowing air onto the heatsink. Most perform better this way, some do work better with the fan sucking.
 
AdvanS13 said:
i was reading someones post stating blowing air onto the heatsink is better in "most cases"

why do most manufacturers set them up to suck out hot air or blow out. and not blow onto? how much of a temp drop will i recieve if its blowing onto the heatsink?

seems like it is working against it blowing onto the heatsink, when heatsinks absorb and release the heat. this would just be pushing it back and also sucking any extra ambient heat wouldn't it?

I assume by "manufacturers" you mean computer manufacturers like Dell. Dell heatsinks suck air off of the heatsink so that their heatsink fan also serves as an exhaust fan for the case.

I would guess that their motives for doing this are a sort of "kill two birds with one stone" type of thing... But I can say for sure that it is definetly not done to get the best performance possible.

I'm guessing again, but it sounds like your concept of the way in which a heatsink functions might be slightly skewed. A heatsink simply transfers heat by increaseing the surface area for heat to conduct to and dissipate from. Air blowing onto the heatsink will not add heat unless the air is warmer than the heatsink; the air blowing onto a heatsink hits the heatsink and deflects off of it and then circulates in the case.

The superiority of sucking vs. blowing depends upon the design of your heatsink and the features specific to your case, components, and wiring. Most heatsinks perform better with a fan blowing onto them because more air hits the bottom of the heatsink more directly. The performance of heatsinks with fans that suck air off of the heatsink can be hurt from the lack of a shroud, which allows the air to kind of "short" the heatsink, with lttle air hitting the hottest parts of the heatsink base and more air going into the fan right by it's intake at the top of the heatsink fins.

One fan that sucks off of the heatsink is this one and it has a shroud:

svcompucycle_1743_1342990


http://www.heatsinkstore.com/alpalheaton.html
 
As stated above, OEMs often suck air off the sink and then duct it outside the case; this performs two functions and does neither as well Performance-wise as dedicated single purpose fans. But it is quieter- and that is why they do it.

That said, experimentation is the way to go ;)

Most people have more success blowing onto the heatsink, most of the time.....but there always exceptions!

You never know if you may have an exception to the rule if you don't try it;)
 
My case has got a set-up with the fan blowing away from the cpu, and it basically jetting towards an exhaust fan blowing out the back of my case.

When I get my SLK-7/Thermaltake SF2 set-up, would that make said exhaust fan pointless?
 
well i tried it. my heatsink is oem, but my fan is a ys tech variation. it actually makes it sound a tad louder. and as far as results...it seems to do the same re****s. and maybe even 1c higher or so for some reason...guessing because of the oem heatsink.

my concept on how heatsinks worked was an assumption, thanks for explaining how they work.

too lazy to turn my fan back around, i like the louder sound so i can tell if it quits on me:D

need to get me a loud smart fan 2:mad:
 
rogerdugans said:
As stated above, OEMs often suck air off the sink and then duct it outside the case; this performs two functions and does neither as well Performance-wise as dedicated single purpose fans. But it is quieter- and that is why they do it.

And people STILL call up and complain that the darned things are too noisy....
 
The advantage to having it suck is that it has the tendacy to get less dust stuck in it. This is not always true but it generally holds true.

Thank you,
Daniel
 
I read this thread and I thought I should maybe turn my Vantec Sunon Tornado 80x38 84CFM fan around.
I currently have it sucking air off of my 1.33ghz 266fsb T-Bird. And at 10.5x133, the temp went to 58*C once, and the system high was 30*C.

THe Vantec Tornado fan is on a SK-7. I have 7 other fans in the computer, all exhaust, and I was wondering if I should make the Tornado fan blow air onto my new processor, 1700+ DLT3C JIUHB, when I get it next week.

Also, do you guys think that its ok to have 7 exhaust fans in my case?, I have 2 exhaust fans on the front lower side of the case taking air off of the hard drive. 1 exhaust fan on the top of the case, and 2 exhaust fans in the back of the case. What do you think I should do to improve my temps with my T-Bird, and when I get my new T-BRED B.
 
well,

I just got a 80->120mm converter and a nice YStyech 120mm fan that blows about 125CFM. ON my Swiftech MCX462+ i used to have a TT SMart Fan II (on full) blowing and my load temps on Prime95 were about 53C, i then used the converter BLOWING onto the heatsink and load temps went UP to 62C, i then tried the 120mm fan SUCKING and the load temps went DOWN to a max of 49C.

Seems like trial and error is the best

NANA
 
ok, thanks bananaman, i'll probably keep the Tornado fan sucking air off my SK-7 like an exhaust fan when I install my 1700+ DLT3C JIUHB next week.
Do you think that my temps are so high since I use a thunderbird chip and its at 1.33ghz? I know they are very hot chips.
 
katka said:
Well I got about a 6C drop in temps when I set my Tornado to blow onto my SLK-800. Never know till you try.

You never know until you try it.

Mine is 2 degree cooler with sucking. Additional bonus: The fan is less louder.
 
yea...i actually think this is increasing the temps 1-2c...now that i have watched the temps a few days.

i think it all depends on what heatsink you have. mine is oem and is designed to suck out not blow on.

and yea, my fan is louder now:D
 
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