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large heatsink will be available by april or sooner

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tms0425 said:

This is from the Conrad site regarding their powder coating:

"Coating Material
Textured black polyester powder coating has been chosen as the standard finish on all coated Conrad heatsinks and provides:

* a quality, durable and attractive finish capable of withstanding elevated temperatures,
* increased thermal dissipation in the order of 5% to 8% (depending on the heatsink) under natural convection."


Wow! I actually thought power coating would run hotter than if it were bare or anodized. That's interesting.
 
labjr said:


How about powder coating? Does this change the thermal properties? I have friends who work in metal production and can easily have stuff powder coated. Anodizing is not so easy to have done, because it's not as popular as it used to be.


I believe Conrad does this, but I have no knowledge of its thermal properties. A black color is used to promote radiant heating, but that is not the primary mode of heat exchange, which is convection (after conduction from the transistor through the heat sink). So it is important for any coating to not inhibit convection cooling.

Fins that are very deep or very long can inhibit air movement through the fins, because the resistance to air movement will increase, and the air will move around and outside of the fins and not draw out the heat. Therefore, if fins are made deeper and longer, the spacing between adjacent fins must increase. It is all a balancing act, like everything else. You just don't make the fins deeper or longer in the expectation that it will be better, especially from a standpoint of economy of materials; at least not without determining the cost/benefit of doing so as opposed to other changes that may be of better benefit.
 
tms0425 said:

This is from the Conrad site regarding their powder coating:

* increased thermal dissipation in the order of 5% to 8% (depending on the heatsink) under natural convection."


I would be interested to know more about this. This statement is unclear what is being compared to what. As this range is in the range of radient improvement for a black color vs. a low emissivity natural color, I'm wondering if the improvement is only to just the radiant cooling (without speaking to any possible reduction of convection cooling), or to the total amount of radiant and convective heat exchange.
 
pooge said:



I would be interested to know more about this. This statement is unclear what is being compared to what. As this range is in the range of radient improvement for a black color vs. a low emissivity natural color, I'm wondering if the improvement is only to just the radiant cooling (without speaking to any possible reduction of convection cooling), or to the total amount of radiant and convective heat exchange.
No idea, just copied the quote from their site. I know it is very durable and does seem to stay black over time unlike most anodized ones.

The surface finish for mounting the transistors is also very flat and clean, so I doubt any added machining is necessary in most cases.
 
pooge said:



I would be interested to know more about this. This statement is unclear what is being compared to what. As this range is in the range of radient improvement for a black color vs. a low emissivity natural color, I'm wondering if the improvement is only to just the radiant cooling (without speaking to any possible reduction of convection cooling), or to the total amount of radiant and convective heat exchange.

Heatsink design seems pretty complicated to me. However, I would have thought powder coating insulates the aluminum inhibiting some of the convection of the heatsink.
 
One would not want to coat the mounting surface with anything, Mounting surfaces should always be bare aluminum or copper.

Aluminum oxidizes over time and eventually corrodes. Notice how some bare aluminum shows evidence of pitting covered by a white colored film?

The oxidation and any corrosion does impact thermal efficiency.

-David
 
hifimaker said:
One would not want to coat the mounting surface with anything, Mounting surfaces should always be bare aluminum or copper.

Aluminum oxidizes over time and eventually corrodes. Notice how some bare aluminum shows evidence of pitting covered by a white colored film?

The oxidation and any corrosion does impact thermal efficiency.

-David
Obviously true. I should have noted that the transistor mounting surface on the Conrads is definitely NOT coated.
 
the applied coating type is only part of the question.
That determines the emissivity and the thermal conductivity.
In addition one must ask how thick the coating is and what surface texture it has.
All these will affect the overall dissipation ability.
I suspect Conrad are comparing a bare untreated aluminium heatsink to their black powder coated version.

Be careful with most powder coating shops. The coatings are often very thick and become very effective (plastic) insulators.
A very fine mist spray of black lacquer is usually better but never looks as good.
 
hifimaker said:
One would not want to coat the mounting surface with anything, Mounting surfaces should always be bare aluminum or copper.

The oxidation and any corrosion does impact thermal efficiency.

-David


tms0425 said:
Obviously true. I should have noted that the transistor mounting surface on the Conrads is definitely NOT coated.

Don't know about oxidation imparing THERMAL efficiency, but it does ELECTRICALLY insulate. Alumimum oxide spacers are some of the best among thermal spacer options between the transistor and heat sink.
 
jtsaudio said:
Yes.
Please offer heatsinks 10-12"wide, with height of 5"-6", with fins running vertically.

You will sell many to the members here!

-Joe

Agreed!

Russell, you are pretty much the only standard supplier of heatsinks on EBay and a lot of us have had very good experiences with you. Your sinks are very good and you have been dependable over the years.

We find ourselves wanting the following features-

- vertical fins
- powder coating /anodizing
- tapped and threaded holes!! (Standard TO-3 or your own known spacing so we can design PCBs or brackets to comply).
- Here is a BIGGIE- "BLANKS" for the front panel, back panel, and bottom/ vented top, with elbows or tapped aluminum corner pieces. Everything tapped/threaded to fit.

With some "blanks" you would go from a heat sink vendor to a heat sink & chassis vendor, and there is a very large need for chassis here. Think about whether you could do this. There is no reliable source of heat sunk chassis with everything the same color. We buy heat sinks and cobble together a front/back panel, top/bottom from other places.

Get a couple of standard sizes, 1U, 2U, 14" deep, 16" deep whatever.

Anyway, you asked and that is my opinion.
 
Member
Joined 2005
Paid Member
Maybe you could work with DIYEnclosures again to get a setup with the large heatsinks. I know he was using your heat sinks on a previous chassis and could probably sell more of his nice chassis' if they were close to the First Watt specs for heatsinking and layout.
 
tms0425 said:
...Textured black polyester powder coating..."[/i]
Not just powder coating :whazzat: Textured ;)
Texturing, beading or sandblasting to increase surface area will make a significant difference.
Personally, I like 3" fins, 1/2" between fins and 1/2" base. 6" wide is good, you can use 2 per side. But, 8" high. :)
Thx
 
flg said:

Not just powder coating :whazzat: Textured ;)
Texturing, beading or sandblasting to increase surface area will make a significant difference.
Personally, I like 3" fins, 1/2" between fins and 1/2" base. 6" wide is good, you can use 2 per side. But, 8" high. :)
Thx

Would a one piece heatsink be better? I ask because on cvillers F5 boards the outputs are spaced only 3.25 inches apart.
 
2 heatsinks would basically be the same as 1 large 1, equal to the size of 2. 2 does allow for electrical isolation without the use of isolators under the transistors. that would give you reduced thermal resistance. 6" wide heatsinks also allows for more universal use as you are not confined to the 1 larger size :D
 
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