churchhaze
Well-Known Member
I've been thinking about this for a while and I'm starting to lean toward the 3.945" at 4" length (almost perfect square) to make heat sinks for a single cxa3070.
It's not as wide of a profile, but look how freaking tall it is, including the base! 2.875 inches tall!, 2.5 inches of that being fin height. That's beastly.
Each 3.945"x4" square sink would have 10 fins, which is 200in^2 area. The area of the base is around 15in^2.
That gives a total of about 215in^2 for one cob.
The 24 inch bar at 4.85 profile for 4 cobs had an area of =967.201934 in^2 (6240 cm^2) as you calculated. Divided by 4, that's ~242in^2
I think the narrower, but taller, profile would actually be a huge advantage, and just might go this beastly route. They'd be 13 dollars a sink, but that sounds like a real bargain.
It's not as wide of a profile, but look how freaking tall it is, including the base! 2.875 inches tall!, 2.5 inches of that being fin height. That's beastly.
Each 3.945"x4" square sink would have 10 fins, which is 200in^2 area. The area of the base is around 15in^2.
That gives a total of about 215in^2 for one cob.
The 24 inch bar at 4.85 profile for 4 cobs had an area of =967.201934 in^2 (6240 cm^2) as you calculated. Divided by 4, that's ~242in^2
I think the narrower, but taller, profile would actually be a huge advantage, and just might go this beastly route. They'd be 13 dollars a sink, but that sounds like a real bargain.
Those are the 5.88" X 24" long. It gives 6240cm² each so that is about 30cm²/dissipation W. So in your case you would need 4560cm² which is about 23" of the 4.85" profile.
One thing to consider though, the 4.85" profile has a base plate that is only half as thick as the 5.88" profile, so that is why I decided against those for COB purposes. The thick base plate helps spread the heat along the length of the heatsink to all the fins faster which is important since the COBs are spaced relatively far apart and each is like a hot spot. So the thick plate decreases the temperature gradient which is exactly what we are after. The 4.85" might be a good option for vegging though because smaller LEDs are normally used and the heat doesnt need to be moved as far.
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