DIY Passive cooling with PIN Heatsinks SST120 and SST140
- Thread starter robincnn
- Start date
JorgeGonzales
Well-Known Member
They are anodizing for a very good reason, it increases the emissivity of the heat sink, see https://en.wikipedia.org/wiki/Emissivity#Emissivities_of_common_surfaces
Compare aluminum foil to anodized aluminum in that chart. It improves the cooling performance of passive heat sinks, and somebody who isn't me could tell you by how much. Anyway, it's a good thing.
PDX Joe
Well-Known Member
Very interesting, thanks for the link. I found this short summary of anodized finishes. It appears that anodized aluminum has large emissivity benefits for passive cooling. But, with active cooling fans there is only a 4-8% gain in cooling effect by adding an anodized finish.
http://www.aavid.com/product-group/extrusions-na/anodize
Abiqua
Well-Known Member
unfortunately I think the emmissivity increase is very minimal...however interesting...
Somebody {supra? sds? } has a few posts on this in the vault between 24-36 months ago
...The emissivity part is correct and ALL thermal design should strive for as close to a blackbody correlation imho, unless someone wants to expand on that theory.......
JorgeGonzales
Well-Known Member
Like I said, I'm no expert but look at table 3 here: http://www.heatsinkcalculator.com/blog/the-importance-of-radiation-in-heat-sink-design/unfortunately I think the emmissivity increase is very minimal...however interesting...
Somebody {supra? sds? } has a few posts on this in the vault between 24-36 months ago
The emissivity part is correct and ALL thermal design should strive for as close to a blackbody correlation imho, unless someone wants to expand on that theory.......
That shows a ~20% difference in temperature from 141 to 168 degrees between the bare aluminum and anodized heat sinks.
"It is evident that the role of radiation for a heat sink cooled via natural convection is extremely important. Significant decreases in temperature can be achieved by simply modifying the heat sink surface by anodizing or painting to increase the value of the surface emissivity."
Airwalker16
Well-Known Member
robincnn
Well-Known Member
@The Dawg
My 140mm heatsink has thick pins so the extra 10mm height of pins helps a lot. Compared the old 140mm and the new 140mm, new 140mm was 2C cooler than the old 140mm.
Does not increase weight much and there is a good performance gain. The extra pin height helps the new 140mm run better at 2.1 amps.
Those Khatods on the new 140 is a great combo. Following your thread.
My 140mm heatsink has thick pins so the extra 10mm height of pins helps a lot. Compared the old 140mm and the new 140mm, new 140mm was 2C cooler than the old 140mm.
Does not increase weight much and there is a good performance gain. The extra pin height helps the new 140mm run better at 2.1 amps.
Those Khatods on the new 140 is a great combo. Following your thread.
The Dawg
Well-Known Member
Airwalker16
Well-Known Member
I'll need 4.
Airwalker16
Well-Known Member
Can you have 4 sq, clear anodized ones within a month? Or do those only come in black?
Airwalker16
Well-Known Member
Alright.
It's just these PCBs I wanna mount I to pin sinks are 3"x4" or so and would be better on a sq I think. I don't know the diagonal length across them is though. 5" according to pythagoereum theorum. Would they fit on a 120 or 140mm round sink? They'll be 50watts.
I guess it'd be pretty close. Only leaves about a 1/4" on each corner to the edge of the circle.
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robincnn
Well-Known Member
3x4 in will fit on 140mm.
With 120mm , 3.5mm of board will be out in corners. 3x4 is 5 diagonal and 5in is 127mm diameter
So 120 is good enough
With 120mm , 3.5mm of board will be out in corners. 3x4 is 5 diagonal and 5in is 127mm diameter
So 120 is good enough
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Airwalker16
Well-Known Member
The square sinks would be so much better though.
BST
Active Member
Any more of those free sinks?
Airwalker16
Well-Known Member
BST
Active Member
Know anything about these sinks.
alesh
Well-Known Member
It's very dependable on how thick the anodized layer is. A thick layer may perform worse than bare extruded alu when cooled actively.
RuRu.The.Half.Elf
Well-Known Member
Hey @robincnn , I can't find a post about it so sorry if it has been asked.. But..
Which 100mm glass optic that matches the sst120? I found a few different sizes on the 'bay. Is it a 120mm base plate? 108mm? I could wait till they get here and use the digi-calipers but I am itching to spend some cash.
Which 100mm glass optic that matches the sst120? I found a few different sizes on the 'bay. Is it a 120mm base plate? 108mm? I could wait till they get here and use the digi-calipers but I am itching to spend some cash.
robincnn
Well-Known Member
For 120mm heatsink the base plate is 120mm diameter.
112mm is the diagonal distance for mounting points on the 120mm heatsink.
Just updated this on website.
- SST 120 is Pre drilled 100mm Glass lens and LEDiL Angelina Reflectors.
- KB-HB100-80 100mm glass lens is compatible with all holders.
- KB-HB100-120 degree glass lens is not compatible with most COB holders unless a spacer is added.
- Glass Lens from different suppliers may not be same. Verify that the diagonal mounting positions are 112mm before buying the lens.