SPCR's 2010 CPU Heatsink Test Platform
Posted: Mon Jan 25, 2010 12:48 am
Discussions about Silent Computing
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time constraints most likely I'm guessingWhat was the reason for not including the HR-01+? AFAIK,
...What?frenchie wrote:I just have one point. When running a quiet CPU cooler (let's say with a fan running at 7 or 9V), the higher the temperature rise over ambient, the more heat you have to exhaust from the case, ie the faster you have to run the exhaust fan(s), and the less quiet your system becomes.
I just have one point. When running a quiet CPU cooler (let's say with a fan running at 7 or 9V), the higher the temperature rise over ambient, the warmer the air you have to exhaust from the case, ie the faster you have to run the exhaust fan(s), and the less quiet your system becomes.
testing outside a case... makes passive cooling tests worthless, since inside a case with a single exhaust fan, you'll have more airflow and completely different end result.you should also include results with no fan,
Not quitefrenchie wrote:Is is correct if I say the following ?I just have one point. When running a quiet CPU cooler (let's say with a fan running at 7 or 9V), the higher the temperature rise over ambient, the warmer the air you have to exhaust from the case, ie the faster you have to run the exhaust fan(s), and the less quiet your system becomes.
Wouldn't a Cooler's fanless performance be relevant in a fanless or semi-fanless system. Semi-fanless system's fan(s) would be off until a preset temperature is reached.jmke wrote:testing outside a case... makes passive cooling tests worthless, since inside a case with a single exhaust fan, you'll have more airflow and completely different end result.you should also include results with no fan,
No doubt a case will impede natural convection cooling to a degree. But the fanless results are still relevant in my opinion. A case such as Silverstone's FT02 (which has "stack effect cooling") could be used instead of the "open air" bed.jmke wrote:in a case there is less "cool" air compared to an "open test" bed; so it would lead to different results;
c_V in this formula, is the c_V of a monoatomic (3/2), diatomic (5/2), etc coeficient at constant pressure used on basics ideal gasses formulas?Air can contain heat. The amount of heat in a certain volume of air is given by (Linearized, which is "good enough" for engineering):
Q=c_V * V * T
As far as I know, copper has better thermal conductivity than aluminium and actually, then most of modern heatsinks use heatpipes based on copper. The little I know about them is that when your heatsink reaches the maximum amount of heat he can conduce by itself, the extra heat is not transferred to the heatsink, thus it is retained by the CPU's capsule, growing the temperatures of the CPU's capsule.As mentioned before, once dynamic equilibrium is established, your fans must move the heat generated by the processor, thus Q/t is fixed
Ok if I have not misunderstanded, the more airflow (at less temperature) is moving around the heatsink, the more Q it can evacuate from the heatsink. So less airflow => more T at the heatsink.RPM= const / T
so the RPM of your fan scale inversely with the temperature of the air.Therefore, the higher the temperature the slower the fans (and the inverse holds true, too).
Until the electronics fail, anyway
Surprisingly, the 130W TDP Intel QX9650 drew only 66W at peak load (including losses in the VRM) on the existing Asus P5Q-EM platform — it ran 20W cooler than the old Pentium D 950. (This result was closely matched in a more elaborate test by Lost Circuits.)
Not really. At the same SPL/rpm, there is no appreciable cooling difference between those fans. We will not change the reference fan unless and until we find a 120mm fan that's clearly quieter at the same airflow level. There are some contenders in the huge Scythe lineup, but we haven't proved it for ourselves yet. Never enough time.danimal wrote:xlnt upgrade to the testing methodology! however, either it's not quite right yet, or i am misunderstanding something?? could someone please clairify this for me???
there is a rather thorny problem with the same reference fan being used on all of the coolers, because it is inferior to the stock mugen 2 fan at higher rpms, by about three degrees, as your earlier tests proved:
http://www.silentpcreview.com/article961-page5.html
Mike, one little thing about this. I don't know so much about heatsinks, how to dissipate heat and so on, but you have to consider that if a heatsink mounted on an OC CPU in this case -which means a great source of heat- can transfer better heat than others, probably at idle temperatures or with less greater sources of heat (other CPUs /non OC-CPU /underclocked/volted CPU), it will work better than the others.MikeC wrote:3) As it stands, the new test platform is most useful for the OC / gaming silencer, who represent a sizable but still minority portion of the SPCR audience. As a result...
The value does not matter. It just needs to be reasonably constant.javitxi wrote:c_V in this formula, is the c_V of a monoatomic (3/2), diatomic (5/2), etc coeficient at constant pressure used on basics ideal gasses formulas?Air can contain heat. The amount of heat in a certain volume of air is given by (Linearized, which is "good enough" for engineering):
Q=c_V * V * T
Well... No, rather an arbitrary volume around the heatsink where the temperature is reasonably uniformjavitxi wrote: In the formula you assume V is the V in litres of your case, isn't it?
Whoa! If your intake temperature is hotter than the heatsink, please take the case out of the oven! I think it is safe to assume that the air is cooler than the heatsinkjavitxi wrote: Also, if the air surrounding is hotter than the heatsink, by the equilibrium of temperatures theory between 2 objects, the surrounding air will transfer heat to the heatsink although the sorruonding air is moving. Am I correct? So, the lesser temperature (then less Q it has) the airflow through the heatsink has, the bigger amount of heat (Q) the airflow can carry out (evacuate) from the heatsink.
So far you are correct.javitxi wrote:As far as I know, copper has better thermal conductivity than aluminium and actually, then most of modern heatsinks use heatpipes based on copper. The little I know about them is that when your heatsink reaches the maximum amount of heat he can conduce by itself, the extra heat is not transferred to the heatsink, thus it is retained by the CPU's capsule, growing the temperatures of the CPU's capsule.As mentioned before, once dynamic equilibrium is established, your fans must move the heat generated by the processor, thus Q/t is fixed
You might be confusing static and dynamic equilibrium. If you would bring two exactly equivalent systems into contact, and one had 80º and one 0º, the static equilibrium would indeed result in both systems having 40º.javitxi wrote: So establishing an airflow through the heatsink will have the ability to carry out so much Q as the equilibrium between the 2 corpses can. I mean, if your heatsink is at 80ºC and you have airflow at 0ºC, then the equilibrium between these temperatures are 40ºC, so at a constant 80ºC by the heatsink, the 0ºC airflow will move out 40ºC. I don't know what the exact formulas are because I have not studied so much about thermodinamics, so I can assume it is not linear but I think it works someway as I have said, does it not?
Correct againjavitxi wrote: Ok if I have not misunderstanded, the more airflow (at less temperature) is moving around the heatsink, the more Q it can evacuate from the heatsink. So less airflow => more T at the heatsink.
In principle, yes.javitxi wrote: The last thing I want to ask you is the following: I've read that the nearest the fins of the heatsink are, the more difficult for the airflow is to move. So, if you have closer fins, you have to blow air at higher pressure in order to circulate it through the fins. More pressure usually means more RPMs from the fan so higher noise. Then, a combo of a heatsink with the 'proper distance' between its fins + a common fan, makes better scores in temperature than a heatsink with closer fins at same fans' speeds. Am I correct?