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Oreo57, let’s take a closer look at the info you posted.
Firstly, - “Matte-black surfaces will radiate much more efficiently than shiny bare metal.”
Why?
You then quoted, - “A shiny metal surface has low effective emissivity”. But areo57, you cut that quoted sentence short.
The full sentence states, - “A shiny metal surface has low effective emissivity due to its low surface area.”
Yes, a flat black surface is just that because it rough, it has greater surface area & absorbs more light. Whereas a shiny surface is shiny and reflects a lot of light because it’s smoother – less surface area. The greater the surface area the greater the radiative cooling (i.e. fins).
Also think of it this way, -how shiny is that metal surface in pitch blackness? An object has no color in the dark. In the dark how could color possibly have any effect on its radiative ability? Surface area does affect radiative ability, in light or darkness.
Your next quote states, - “Unless the component is facing a hotter surface nearby, it is imperative to
have the heat sink surfaces painted or anodized to enhance radiation.”
The author neither states why or how “painting” or “anodizing” enhances radiation, or the color the paint or anodizing should be. Black is not mentioned.
Which brings us to your last quote. – “Heat sinks cooled by natural convection may benefit from an anodized finish”
But, further along in the article it is stated, & I quote “The color of the anodized finish makes little impact on emissivity since most radiational heat loss occurs at wavelengths higher than visible light."
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