Hi,
Has anybody tried to improve heat sinks by using hydrochloric acid ?
I tried , and the surface of heat sink became rugged.I have not made any mesurements yet , but i suppose that rugged surface should dissipate heat better than a flat one.
The heat sink i used was not anodised , so it is worth to try
Regards,
Lukas.
Has anybody tried to improve heat sinks by using hydrochloric acid ?
I tried , and the surface of heat sink became rugged.I have not made any mesurements yet , but i suppose that rugged surface should dissipate heat better than a flat one.
The heat sink i used was not anodised , so it is worth to try
Regards,
Lukas.
Interesting. I guess you could argue that the rough surface combined with the air flow produces micro-turbulence that aids in the air accessing the heatsink. You might also say the turbulence hinders the free flow of air? A fine point, I know.
If you have a h/s with a fin arrangement that ensures a good transfer of heat as is, and if the air is approaching saturation from the heatsink's point of view (approaching the same temp as the h/s) then surely its presence is unwanted, and good flow is wanted.
I used to read car magazines and there was a misconception once that if you put a flow restrictor in place of the thermostat, the water will linger longer in the radiator and would get colder. Of course, the best heat transfer is made when the difference in temperature between the water in the radiator and the outside air, is greatest, and that means flow.
I may have gotten carried away here (thanks, it was fun).
If you have a h/s with a fin arrangement that ensures a good transfer of heat as is, and if the air is approaching saturation from the heatsink's point of view (approaching the same temp as the h/s) then surely its presence is unwanted, and good flow is wanted.
I used to read car magazines and there was a misconception once that if you put a flow restrictor in place of the thermostat, the water will linger longer in the radiator and would get colder. Of course, the best heat transfer is made when the difference in temperature between the water in the radiator and the outside air, is greatest, and that means flow.
I may have gotten carried away here (thanks, it was fun).
Hi,
I'm inclined to think your
The added roughness also has the secondary benefit of increasing the air contact surface area. This, I think, promotes increased heat transfer. I realise that conduction is not at play here but I stand by that supposition.
But do not add roughness to the interface with the active devices that need the cooling.
I'm inclined to think your
outweighs all other characteristics.
The added roughness also has the secondary benefit of increasing the air contact surface area. This, I think, promotes increased heat transfer. I realise that conduction is not at play here but I stand by that supposition.
But do not add roughness to the interface with the active devices that need the cooling.
I would bet that improvement is very small if not neglible.
Painting your heatsinks can improve emission coefficient from something like 0.2 of bare aluminium up to 0.9
(effect on temperatures is much smaller because convection cooling is dominating effect in these temperatures. )
BTW: It doesnt matter if they are painted black or white, visible color has very little to do with emission coefficient in far-IR range.
Painting your heatsinks can improve emission coefficient from something like 0.2 of bare aluminium up to 0.9
(effect on temperatures is much smaller because convection cooling is dominating effect in these temperatures. )
BTW: It doesnt matter if they are painted black or white, visible color has very little to do with emission coefficient in far-IR range.
The best thing you can do to increase your heatsink's performance is to improve the thermal junction. If you are losing most of the heat transfer in the junction, a 0.01% increase in dissipation is not going to help much. (edit: be careful the type and thickness of paint... heavy house paint is probably not your friend! )
A thick mica washer is going to kill the heat transfer. Silicon goop grease is better unless you need the electrical insulation. A phase-change material is expensive, retail, but you get some ridiculously good thermal coupling. I am still trying to figure out how to unload (hopefully sell) a few thousand pats of Powerstrate and until I do, I am using it. My PC processors are in cool-city now. two down, four thousand to go. Before that, I used the goopy stuff. If I have to use mica, I always try to shave it a little thinner than I found it... The amp in my car, I shaved some of the washers to 1/3 their original thickness and still had plenty!
Another idea is being worked on by the engineers at Innovative Fluidics, with their fan-replacement technology, coming soon to some BIG electronics name brands near you. The details are top-secret but very cool (pun intended).
A thick mica washer is going to kill the heat transfer. Silicon goop grease is better unless you need the electrical insulation. A phase-change material is expensive, retail, but you get some ridiculously good thermal coupling. I am still trying to figure out how to unload (hopefully sell) a few thousand pats of Powerstrate and until I do, I am using it. My PC processors are in cool-city now. two down, four thousand to go. Before that, I used the goopy stuff. If I have to use mica, I always try to shave it a little thinner than I found it... The amp in my car, I shaved some of the washers to 1/3 their original thickness and still had plenty!
Another idea is being worked on by the engineers at Innovative Fluidics, with their fan-replacement technology, coming soon to some BIG electronics name brands near you. The details are top-secret but very cool (pun intended).
two things which improve heatsink performance -- mount the fins so that they are aligned vertically -- this improves air flow -- second -- you can use a small fan -- purloined from a PC power supply and run at a low voltage -- even a small increase in air flow will have a dramatic impact upon the heat dissipated. A small fan run at 70% of its stated voltage is un-noticeable.
For my 2x120W bridged LM4780 amp I arranged 2 heatsinks as a wind tunnel and drove the chamber with a 5" fan -- I isolated/insulated the heatsinks instead of the chips to save eliminate the 0.4 C/W thermal impedance which a mica washer would present to the device. The heatsinks are kept away from prying fingers by their enclosure in a steel chassis. The whole schmegege makes a lot less noise than the hard drive in the TIVO !!!
For my 2x120W bridged LM4780 amp I arranged 2 heatsinks as a wind tunnel and drove the chamber with a 5" fan -- I isolated/insulated the heatsinks instead of the chips to save eliminate the 0.4 C/W thermal impedance which a mica washer would present to the device. The heatsinks are kept away from prying fingers by their enclosure in a steel chassis. The whole schmegege makes a lot less noise than the hard drive in the TIVO !!!
They are hard to find though. I bought some of these spacers:Tweeker said:BeO is a breathtakinglyeffective washer material. Its more thermally conductive than the aluminum.
http://cgi.ebay.com/THERMOCONDUCTIV...goryZ4660QQcmdZViewItem?hash=item200053076077
I'm pretty sure they are BeO. The bad thing is is, he's asking quite a lot at 40 cents each, compared to mica, and they are a good deal thicker.
These are best drilled underwater, which not just cools the bit, but prevents the toxic dust from becoming airborne and breathed in.
If anyone knows any other source of thinner BeO insulators, please post it.
I'm a little late here, but I just saw the idea about chemically etching the heatsink to roughen the surface. You'll get a rougher surface, but will it increase dissipation or decrease it?
Golf balls are dimpled because the rougher surface (compared to a smooth ball) traps and holds a boundary layer of air against the surface of the ball. That boundary layer of air slides through the air more easily than a plastic ball slides through air, so dimpled balls fly farther.
The roughened heatsink may trap a boundary layer of air better than a smooth one. Will the heat transfer improve or will the boundary layer heat up and trap heat in the heatsink? It seems like convective air flow will increase in speed, suggesting that more air will pass over the fins in a given amount of time, suggesting better cooling. OTOH, the velocity of air over the surface of a golf ball is much greater than the convective velocity of air over a heat sink, so maybe the whole concept doesn't apply unless you're using a fan to move the air at high velocity.
The only way to tell is try it and make some measurements, unless you have access to some good thermal simulation software...
I_F
Golf balls are dimpled because the rougher surface (compared to a smooth ball) traps and holds a boundary layer of air against the surface of the ball. That boundary layer of air slides through the air more easily than a plastic ball slides through air, so dimpled balls fly farther.
The roughened heatsink may trap a boundary layer of air better than a smooth one. Will the heat transfer improve or will the boundary layer heat up and trap heat in the heatsink? It seems like convective air flow will increase in speed, suggesting that more air will pass over the fins in a given amount of time, suggesting better cooling. OTOH, the velocity of air over the surface of a golf ball is much greater than the convective velocity of air over a heat sink, so maybe the whole concept doesn't apply unless you're using a fan to move the air at high velocity.
The only way to tell is try it and make some measurements, unless you have access to some good thermal simulation software...
I_F
Trapped air does nothing to help improve the performance of a heatsink -- you have to get the warmed air out quickly. I believe that turbulence is one of the reasons that pinned heatsinks, given the same surface area, perform less well than flat surface heatsinks.
This being said, if you think of moving a viscuous fluid, the grooving on the fins will cause all the ducks to point their noses in the same direction and quickly exit.
Why hasn't anyone mentioned anodization? -- black radiates better.
This being said, if you think of moving a viscuous fluid, the grooving on the fins will cause all the ducks to point their noses in the same direction and quickly exit.
Why hasn't anyone mentioned anodization? -- black radiates better.
Also, what would be the effect of putting a flat plat over the fins with a relatively narrow opening at the bottom? The chimney effect would increase the velocity of the airflow, and presumably the cooling effect if turbulence didn't increase too much.
OTOH, if this (cheap) fix works, it's not clear why manufacturers aren't using it to cut down on the size of expensive heatsinks.
Aengus
OTOH, if this (cheap) fix works, it's not clear why manufacturers aren't using it to cut down on the size of expensive heatsinks.
Aengus
Hi,
my view is that the micro roughness will hold onto a thicker boundary layer. This will insulate the hot surface from the cooling airstream and thus reduce the effectiveness.
Blackness seems to vary.
I have seen tables for various blackened surfaces and was surprised at the winners in emissivity. And how well some non black surfaces did in the competition.
my view is that the micro roughness will hold onto a thicker boundary layer. This will insulate the hot surface from the cooling airstream and thus reduce the effectiveness.
Blackness seems to vary.
I have seen tables for various blackened surfaces and was surprised at the winners in emissivity. And how well some non black surfaces did in the competition.
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