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Old 10-28-2008, 04:58 AM   #1
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Default Opinions on fans blowing or sucking?

Why do most companies want there fans to blow on to the heat sink whether it be on an esc or on the motor? Because when it is blowing on it this creates a higher pressure and with that becomes heat right? so with sucking just the fact of that it is creating low pressure it will help with cooling! What do you think?



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Old 10-28-2008, 05:08 AM   #2
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Put your hand on the "suck" side of a fan and then on the "blow" side of a fan - the pressure is much greater on the blow side, that means more air for cooling.

The fan pulls in air from a wide area and blows it on a much smaller area.

The warming effect of greater surface friction from airflow would be pretty insignificant.
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Old 10-28-2008, 05:21 AM   #3
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Quote:
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the pressure is much greater on the blow side
High pressure is hotter though so it creates a bit heat that isnt needed

Quote:
Originally Posted by sosidge View Post
The fan pulls in air from a wide area and blows it on a much smaller area.
So that is creating heat with pressure





And what if it is a hot day, blowing hot air into a high pressure area on to a hot heat sink
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Old 10-28-2008, 06:34 AM   #4
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you won't generate any heat from the pressure of a fan. I would say blowing, as the 'suck' side draws air fro mall directions, and blows it in one direction. so mounting the fan on the blow side will improve efficicency (ie amount of air passing heatsink).
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Old 10-28-2008, 06:40 AM   #5
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Quote:
Originally Posted by Drifting101 View Post
High pressure is hotter though so it creates a bit heat that isnt needed



So that is creating heat with pressure





And what if it is a hot day, blowing hot air into a high pressure area on to a hot heat sink
Yeah high pressure like in an air compressor generates heat but a fan makes crap all pressure and wouldn't heat up the air at all.
I rekon blowing on you motor makes a bigger difference but it'd be worth trying both.
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Old 10-28-2008, 07:43 AM   #6
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it wouldn't cause any noticeable heat. 1st law of thermodynamics no energy can be lost or gained only transferred.
so give the fan has one form of energy electricity, and brush less motors used in most fans are above 90% efficient there is not enough energy transferred to heat to affect the temperature of the air let alone when u take into account that the air is flowing.
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Last edited by aus jd 2703; 10-28-2008 at 07:47 AM. Reason: re-thought a simpler answer
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Old 10-28-2008, 07:50 AM   #7
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it wouldn't cause any noticeable heat. 1st law of thermodynamics no energy can be lost or gained only transferred.
so give the fan has one form of energy electricity, and brush less motors used in most fans are above 90% efficient there is not enough energy transferred to heat to affect the temperature of the air let alone when u take into account that the air is flowing.
gotta love engineering at uni
damn you, I was trying to avoid mentioning the laws of thermodynamics
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Old 10-28-2008, 07:56 AM   #8
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fans blow, extractors suck.

What you want is to remove the heat generated by the motor, so you blow on it.

You can test this by burning youself with a soldering iron (if you are that way inclined) and see if "naturally" you blow on it or suck the burn...
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Old 10-28-2008, 08:27 AM   #9
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You can test this by burning youself with a soldering iron (if you are that way inclined) and see if "naturally" you blow on it or suck the burn...

Thats a good way to look at it!
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Old 10-28-2008, 08:32 AM   #10
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has anyone else realised how wrong the title of this thread is?
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Old 10-28-2008, 08:34 AM   #11
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When I'm hot, I usually point the fan toward me....I never stand behind the fan to cool off
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Old 10-28-2008, 08:38 AM   #12
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Besides, you wouldn't want to pull all the heat from the motor through the fan. This would shorten the fan's life significantly as it is air-cooled as well. Especially when strapped to a heat-sink...

PS: Which side of a fan do you cool yourself with? (P2 beat me to it... )
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Old 10-28-2008, 09:16 AM   #13
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Quote:
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When I'm hot, I usually point the fan toward me....I never stand behind the fan to cool off
Ha ha. Makes sense...
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Old 10-28-2008, 10:15 AM   #14
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Could we get this thread moved to the NORCAR/Gate forum?

Thanks.
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Old 10-28-2008, 06:28 PM   #15
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Originally Posted by ~McSmooth~ View Post
Could we get this thread moved to the NORCAR/Gate forum?

Thanks.
Why?




Ok thanks for all the input guys but i will still test this with my new lrp heat sink and the 40x40 fan
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