More fins or less fins....THAT is the question......

[quegyboe]

I have been spending some time thinking about this dilema....I currently have a "Best CPU Cooler" HSF, and I noticed something about it. The fins are very close together and this seems to limit the amount of air flow throught them....so I started thinking...if I was to buy or make a HS that had long, spaced out fins and a thin base, and added a 5000 - 7000 rpm fan, (like the one I have on my current HS), then wouldn't the heat dissapation increase due to the more air able to travel over the HS more quickly? I just want opinions on the theory as I might try it out when I get home.....Thanks!

 

[Phil]

smaller fins give a greater suface area for air to absorb heat from which makes them more efficient

 

[Hoot]

You gotta think of heat conductors like electrical conductors. The smaller the conductor, the greater the resistance to heat flow and the less heat is available for air removal at the end of the conductor. So, there is a point of diminishing return for long skinny fins, even if you can fit a lot of them in a given area. As you pointed out, there is also a point where they can be packed so densely as to restrict the ease of airflow over them. I have yet to see an HSF where that occurred, but enter the variable of turbulence and shape of the fins become almost as important an issue as thickness and density. If their pattern upsets the natural airflow pattern of the given fan you are using too much, then airflow decreases also. It is an equation with many variables. I admit that it amazes me that we can achieve the degree of passive cooling with the T-bird and Duron considering the small area relegated on them for passing the heat and the material it is made of.

 

[Phil]

Intel uses heatsinks with wafer thin fins on it's pre-release chips that it show's to the press etc and these don't need a fan becasue of how efficient the fins are at giving off heat