Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
Is there a formula that calculates how much the C/W changes according
to fan cfm?
Yes, the formula for C/W according to fan cfm is specific to a given heat
sink design and a given fan size (80x25, 92x25, 70x15). The formula is
derived from empirical lab data and is a best guess based on the lab data.
Here are a few of the variables; flow direction of the fan, does the fan
operate at a constance speed, are there dead air spots, air pressure behind
the fan, thermal properties of the HS material, air resistance of the fin
design, homogenous composition of the HS material, fin design of the HS, air
flow properties of the HS (lam or turb and at what point in the HS), ect.
All these variables can change with time. This is why a vantec tornado fan
(80x38) may not cool any better than a high speed sunon (80x25) or why the
thermaltake V12 uses a three blade fan (higher pressure). There are allot
of factors involved and most are dynamic. A good rule of thumb is to use a
high pressure fan on a microfin HS that will produce a constance cfm. For a
non-microfin HS use a high flow cfm fan. It is always a good ideal to use a
variable resistor to control the fan speed to optimize the noise/cooling
efficiency ratio.
A high cfm may not always be the answer to better cooling. For instance I
have a TT slientboost HS with a vantec tornado fan on a variable resistor at
12V and 5600 RPM the differential cooling is the slightly better (<1°C) than
~9V and 4500 RPM but the noise level of the fan increases exponential. A
low pressure high cfm (80x25 sunon or TT) fan does very poorly on this HS
due to the micofin design where as a high pressure fan relatively lower RPM
works great. The TT V7 which has a wide spaced fin design and copper core
works best with a low pressure high cfm fan (92x25). The swiftech HS design
appears to work better with a high cfm fan and high pressure although some
people have gotten good results with a high cfm low pressure fan pulling air
through the swiftech HS rather than pushing air though the HS due to it's
radial pin design.
"Ken" <___ken3@telia.com> wrote in message
news:r137j0lqd3vid83ue9qinlq7aiob9g750d@4ax.com...
> On Mon, 30 Aug 2004 08:58:21 -0400, Philip Wright
> <pvwrght@attglobal.net> wrote:
>
>> What cooling devices are group readers using on Prescott cpu's?
>> This will be going into a P4C800-E Deluxe.
>
> Thermalright SP-94 is a very good cooler used with a silent 92mm fan.
> http://www.thermalright.com/
>
http://www.hardwaretidende.dk/hard/artikel/03/10/10/5075375
>
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