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Question for all you DIY LPMers

C

cilegray

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By polishing any heatsink, you also reduce it's efficiency by effectively reducing it's surface area for heat exchange with air, as opposed to a slightly rougher piece.

The only part you would want to have really really smooth would be the area directly in contact with your heatsource, for better exchange.
 





lasersbee

lasersbee

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SCOTTIEMANN21 said:
anyways I think I have enough info that for this specific aplication matte black is the way to go... atleast when it comes to less professionally made LPMs.
Click to expand...
Are you saying that companies like Coherent... OPHIR.... Newport.... etc
are not professional... I have at least 10 Heads from these sellers
that are Flat Black....:D ;)


Jerry
 
S

SCOTTIEMANN21

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Sorry Jerry,

deffinitely worded that wrong.

even though I completely agree with you that matte black is the overall best surface to be used for a heatsink in almost every application, I still would like to get my hands on a thermal camera because I think it would be very interesting to see the different effects the surface has when dealing with this type of application and especially when the heat generated and dissipated is coming from a light source, regardless of the fact that we know matte black will have the better outcome.

wouldnt you like to see the effects visually? or do you have thermal cameras built into your eyes:crackup:

anyways I do enjoy your way of directing my thought towards the right answer rather then blatently giving in answer.. it actually helps me realize other factors I didnt realize.

:beer:

-Scott
 
lasersbee

lasersbee

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SCOTTIEMANN21 said:
Sorry Jerry,

deffinitely worded that wrong.

even though I completely agree with you that matte black is the overall best surface to be used for a heatsink in almost every application, I still would like to get my hands on a thermal camera because I think it would be very interesting to see the different effects the surface has when dealing with this type of application and especially when the heat generated and dissipated is coming from a light source, regardless of the fact that we know matte black will have the better outcome.

wouldnt you like to see the effects visually? or do you have thermal cameras built into your eyes:crackup:

anyways I do enjoy your way of directing my thought towards the right answer rather then blatently giving in answer.. it actually helps me realize other factors I didnt realize.

:beer:

-Scott
Click to expand...

Yeah... I've found that when one needs to think about a
solution that it sticks with one longer than when one is
spoon fed...;)

BTW... you may find that a non cooled thermal camera
might not pick up the minute temperatures differentials
of a TEC Thermopile Sensor that can detect the radiated
heat of your hand...

What is the temperature resolution of a Thermal camera
that does not cost $100K....:thinking:
I think I'll Google that....:D


Jerry
 
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S

SCOTTIEMANN21

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I dont even want to know Jerry cuz I cant afford it anyways... Im still waiting for a few extra bucks to pick up a couple of DTRs cheap 445nm diodes so I can put together a couple watt blue labby :evil:
 
Sputnik77

Sputnik77

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A black surface does indeed radiate heat better!!!!


I think the main reason the pros anodize black, is it simply looks more professional, and keeps the parts looking good while they sit on the shelf. While they may claim its to radiate heat better (which it does) to make it sound more "engineered", I think that is simply an "added bonus". It just simply looks more professional, and it does add corrosion and discoloration prevention. If Coherent, Ophir etc. didnt anodize their heads, the time spent on the shelf before they are sold is enough to make bare aluminum look "dingy", and not a very presentable product. Yes, bare aluminum can become discolored, especially if its a dusty environment. It happens all the time with parts at work, and we have resorted to chemical brighteners to make them look "new" again if they have been on the shelf long enough. If its been a LOOOONG time, and depending on the alloy, aluminum oxide can actually start to be visible as a white dusty looking surface. Bottom line, IMHO , I think its more of a manufacturing/sales decision more than an engineered solution to a thermal issue.
 
S

SCOTTIEMANN21

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yea the cheapest handheld ones I can find are about $1000 to $2000 but like you said they probably cant pick up the minute differences in temp that we are dealing with...
 
lasersbee

lasersbee

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Sputnik77 said:
A black surface does indeed radiate heat better!!!!


I think the main reason the pros anodize black, is it simply looks more professional, and keeps the parts looking good while they sit on the shelf. While they may claim its to radiate heat better (which it does) to make it sound more "engineered", I think that is simply an "added bonus". It just simply looks more professional, and it does add corrosion and discoloration prevention. If Coherent, Ophir etc. didnt anodize their heads, the time spent on the shelf before they are sold is enough to make bare aluminum look "dingy", and not a very presentable product. Yes, bare aluminum can become discolored, especially if its a dusty environment. It happens all the time with parts at work, and we have resorted to chemical brighteners to make them look "new" again if they have been on the shelf long enough. If its been a LOOOONG time, and depending on the alloy, aluminum oxide can actually start to be visible as a white dusty looking surface. Bottom line, IMHO , I think its more of a manufacturing/sales decision more than an engineered solution to a thermal issue.
Click to expand...

There have been a lot of different colors of anodizing available
for quite a long time now for corrosion resistance...
Red... Blue... Yellow.. Cadmium... etc.. Yet the only colors that
the Professional Thermopile manufacturers seem to use is Black...

For looks alone a sexy Clear Red or Blue Anodized head would
seem the way to go but that is not the case...
I have a feeling I know why...;) :beer:


Jerry
 
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SCOTTIEMANN21

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I like to anodize my sportbike parts purple but then again i recently painted my bike 2 tone black metallic and gunmetal metalic from a multicolor metallic red
 
Cyparagon

Cyparagon

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Sputnik77 said:
A black surface does indeed radiate heat better!!!!
Click to expand...

Pretty much everything is black in the spectrum it emits anyway. That is to say objects (even objects painted white) will absorb mid-IR light and are therefore "black." Anodizing has the effect of turning the metal "black" as well.

In most heat sinks, convective currents do most of the work. There isn't much to be gained by painting them since paint is an insulating layer. The small increase in radiative cooling will be offset by the decrease in convective cooling. It depends on the situation - that's why some are black/anodized and some aren't. Also, it might not be worth the expense of additional processing. "gud 'nuff."
 
S

SCOTTIEMANN21

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one thing I learned in art class... black is the absence of color and white is the combination of all colors...

anyways anodizing doesnt cost me anything so Ill just anodize it black
 
H

honeyx

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I think there is no need to argue about black bodies absorbing heat faster and radiating heat faster than other colored bodies, because that´s a sientic proven fact.

I also agree with Cyparagon that a paint in general is an isulating layer. But even black paint can improve heat absorbtion and radiation.

Remember an officialy made test with cars in winter. They took a white painted car and a black painted car and measured the temperatures. The black one cooled down faster and also reached a deeper temperature. The difference was about 2 degrees of celsius, so not a very big difference but noticable.

So all Jerry said is true and makes sense.
 
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H

honeyx

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Dude. There is a world beside the Internet. This was shown some years ago on TV so no link aviable. (Maybe there is already a video aviable somwhere on the net, but I don´t remember which channel this was and when this was emitted exactly on TV and am not able to give you a link for everything)

It´s simple. The black car cooled down over night to the exact same temerature like outside. It was -9C if I remember correctly. The white car cooled down to -7C. So it was inside 2C warmer than outside.

No doubt, if they would leave both cars for a longer period than just over night in a dark environment and the outside temperature would be kept constant, both cars would cool down to the same temperature, but they didn´t do that because they wanted to show the results you can expect from different colored cars the next morning under real conditions.
 
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