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Push vs Pull on a Rad?

BALISTX

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Feb 12, 2007
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Ottawa, ON
I vote for push, as it would be far more efficient to push cooler air through the rad fins then trying to pull the hot air out. When pushing the cool air through the rad you are more efficiently cooling the fluid inside the rad.
 

3.0charlie

3.0 "I kill SR2's" Charlie
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Push: air back pressure against the rad fins; small distance between fan and fins does not allow for a proper laminate airflow (read turbulent air); lower-CFM needed, since air mass is at fan intake.

Pull: no back pressure against fins; lamintate airflow at rad intake; higher-CFM fan needed since air mass is further away from fan intake.

Basically, there's no difference (ok, maybe ~1C lower for pull). It's more of an installation requirement (clearance) than anything else.
 

Babrbarossa

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Push!: Hot air is 'bigger' than cool air- pull cool air in and you're using smaller hot air to create the negative pressure to do so, meaning you're pulling less air- push cool air through and you moving large amounts of denser air which gets bigger on the way through: more air friction and flow
 

3.0charlie

3.0 "I kill SR2's" Charlie
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more air friction and flow
Air friction equals turbulence which equals loss of laminate airflow. If the boundary layer is compromised by the turbulence, your heat exchange between fin and air will be reduced.

Think about a car radiator, with the fan in pull condition. Or another example (in which I know a lot more) are aircraft turbine engines, where the fans (the high-pressure compressors) are located after the combustion chambers.

john
 

Babrbarossa

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The major difference is that those examples primarily use airflow that is NOT supplied by the fan (from forward motion) and you're right- in those cases, if the fan were in front pushing, it would disrupt that flow and create turbulence
 

MpG

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Aug 2, 2007
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Kitchener, ON
Taken from the FAQ on Thermochill's webpage:
For best temps on the PA series, testing currently shows PUSH to be the best solution... shrouded vs unshrouded exhibits minimal benefits, in the region of upto 2%. Fans pushing as opposed to fans pulling exhibits increases of upto 4%, and is roughly equivalent to running a shroud with fans in a pull configuration.
 

3.0charlie

3.0 "I kill SR2's" Charlie
Joined
May 22, 2007
Messages
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4% of 50*C is 2*C. My Q6600 and E6400 have temperature swings higher than 2*C. Like I stated in my first reply, it does not make any substantial difference.
 

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