Laser BEAM heat and Heatsink Coloring..

[Benm]

If you want to do a comparison test, you really need to use heatsinks that are identical in size and shape. Radiation is only a small part of total heatsinking capacity, when dropped in free air on the floor like that, convection will be the biggest factor by far.

As far as getting lower readings on the FLIR for surfaces that are less emissive: it doesnt have to be like that. Afaik FLIR actually measures different parts of the IR spectrum and uses the ratios between them to calculate the temperature. As long as the albedo of the heatsinks is flat across the ifrared, its absolute value should have little effect on the temperature detected.

 

[qumefox]

I pretty much said that already.. The part about needing to use similar heatsinks for comparison anyway. And I got jumped on for it. heh.

 

[Cyparagon]

The heatsink on the right has less surface area and slightly more mass than the heatsink in the middle. If anything, it should read higher. Look at them - Is it really plausible that one cooled 50F more than the others in ~5 seconds?

As far as getting lower readings on the FLIR for surfaces that are less emissive: it doesnt have to be like that. Afaik FLIR actually measures different parts of the IR spectrum and uses the ratios between them to calculate the temperature. As long as the albedo of the heatsinks is flat across the ifrared, its absolute value should have little effect on the temperature detected.

If that is true, it is only true to a certain extent. I can tell you from experience, shiny metals always read low or don't read at all, that is to say they reflect the light from other sources, and you just read the temp of whatever the reflection is.

I'll try it again with two different IR thermometers and report back.

edit:
This time without even taking them out of the oven: One read "Hi" and the other read (from left to right) 97 99 83 C

This is the only claim I'm making: Black (in the visible spectrum) doesn't necessarily mean an object radiates more heat.
The flaws in the method do not explain why one consistently reads much lower than the other two.

 

[BShanahan14rulz]

a black body radiator should be efficient at both absorbing and radiating, right?

I believe the results of Cyparagon's tests should be useful if that bit is true.

It was stated that his test only shows which heatsink absorbs heat better. Well, all three are aluminum, and if one absorbs heat better, that is a sign that it absorbs radiation more efficiently. If it absorbs radiation more efficiently, ought it radiate more efficiently as well?



(Also, air pocket shouldn't matter when talking about radiated emission rather than conductive heat transfer. And anodizing increases surface area by A LOT [scientific term]. I realize that was quite a few posts up, but it somehow slipped by me that we are talking about radiative transfer)

As long as we're making claims, I still stand by my assertion that anodized heatsinks are better than plain aluminum heatsinks. For convection cooling, the difference is minimal, but for radiative cooling, the anodized heatsinks are much better.