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Originally Posted by AAngel
I still don't get it. The sink obviously doesn't have any mass, so it can't pull much heat away from the esc before it gets to be as hot as the esc is. It has to rely on dissipating the heat into the air around the fins and then getting that hot air out and cool air in to repeat the process. I don't see how you can say that the sink will work without fans. So, this thin aluminum has all of these fins with the purpose of moving the heat from the sink to the air around the fins. So what happens when the air around the fins is the same temp as the sink itself and there's no fan to get the hot air out and cool air in. You have to move the air, because, as I said, air is a horrible heat conductor. The hot air isn't going to pass its heat off to the air around it.
I also don't know how you can say that the sink effectively dissipated that much heat with very little air flow. I'm going to assume that you are talking about the sink being inside of a computer case. If that is true, you can't say that there isn't a lot of air flow. Not only are fans in computer cases designed to move air, but they are placed inside the cases in places where they will be the most effective.
I'm also not getting your mentioning more fins working better with higher airflow and fewer fins working better with lower air flow. I can understand that if you have a given area with say 10 fins, you have to have a higher pressure air flow to cool it than the same area with 5 fins. It's kind of like flowing water through a pipe. With a 1" diameter pipe, you'd have to have a higher pressure/flow to move X amount of water in a given time than you would with a 2" diameter pipe. The larger pipe can flow the same amount of water at less pressure, but it is none the less moving the same amount of water. In this case, since you have lots of fins, the pressure of the air going through the fins is going to be higher than it would be if your sink had fewer fins. Are you saying that your sink is going to work better in this case with little air flow. If so, I'm not following.
I'm not trying to be argumentative. I'm must hoping to learn something.
It still seems to me that attaching the esc to the chassis is the best way to keep it cool. Lots of surface area, inspite of the lack of fins, and lots of mass to store heat until it can be dissipated. I wonder how long it would take an esc to heat a chassis up to 160 degrees F.
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About the fewer fins working better with a lower airflow FAN I meant to say, also, when each individual fin is larger too. For a larger # of fins, they are usually small, and more densely packed, correct? So, for a given fan, it has to overcome alot more back pressure (because of surface area of fins, skin resistance), thereby reducing the overall amount of air actually traveling through the fins.
Another example, the PC i'm on now is highly overclocked, running a core 2 duo 2.4 overclocked to 3.6ghz. This takes upping the core voltage, and frequency, and some other settings.... anyways, the heat dissipation goes from the rated 65watt TDP, up to approx. 110 watts of heat at 100% CPU usage. The heatsink I am using is a large tower heatsink, anyways, it doesn't matter if I turn the heatsink fan ON, or OFF, the CPU temperature increases only up to 2 degrees. So then, the only thing keeping some cooler air inside the fins is the airflow through the case, which isn't a whole heck of alot.
This heatsink does have some mass to it btw, it's approx. 120 grams, or was it 140 grams, can't remember, it's on a previous post.
To get to the point, this heatsink will have more than enough airflow to work wonders if situated in a half decent spot.
Just for reference, I measured each fin, and came up with this surface area. Total surface area is about 1.23 square meters of area. The heatspreader is 2.5mm thick, the fins are .4mm thick, and the fin spacing is about 1.6mm.
The thin fins have something to do with not needing much airflow to stay cool. The amount of heat energy present with a Quark will won't need much like i've said before. It should have plento-airflow however. Also, surface texture has alot to do with surface resistance (obviously), they have a fine gold ball texture to them, with cuts down on resistance.
One last comment, when I was grinding this thing, after I took it off from heavy grinding, a few seconds, and the area I was grinding was only luke warm, before that I could not touch it; that was after moving the heatsink back and forth a few times in the air, not very fast either. It simply doesn't need much to work properly, it's an efficient cooler.