These days I built a wall-wart powered worklight using a 10W LED and a Hammond aluminum enclosure.
At first I left the enclosure blank, and when I did a temperature test, the light began to heat up until after 20 minutes, it reached 55 °C, temperature still rising, and then I pulled the plug.
Today I painted the enclosure black, using matte acrylic paint. The case temperature after 20 minutes was 49 °C, and after 30 minutes it wouldn't go above 52 °C.
It seems that a matte black surface helps a lot in dissipating heat. I reckon that anodising helps even more than just regular black paint.
It radiates heat, air has nothing to do with it, heat is lost by conduction, convection or radiation, when your in front of a fire your feeling radiation (or the sun’s rays), warm air or something warm to the touch is conduction (physical contact), these are the two main flashlight heat shedding mechanisms.
bare metals are poor radiators of heat, anodization is an excellent radiator
This also goes to show that, for a light, heat loss by radiation is more important than heat loss by natural convection at ordinary temperatures - at least provided the light has no provisions (like fins) to enhance heat dissipation by radiation. As far as anodization, Imwould figure that this would improve heat dissipation even more than paint. With paint, heat must be transferred through both the interface between the paint and aluminum and the paint itself. And the thermal resistance of both of these factors would be improved by anodizing rather than painting. Of course, anodizing would improve heat loss by convection for the same reason. On the other hand, a bare aluminum surface would certainly dissipate heat better by forced convection.
Not necessarily… radiation rate determined by the emissivity of the surface… which is determined by things like the material and its surface treatment. Shiny, smooth, and reflective things don’t radiate well. Coarse black things do. You can have a rather smooth, shiny, reflective anodized surface that does not radiate well. A textured black anodized surface generally does.
Here are some pictures of the abomination I built.
I drilled holes in the top and bottom, so air can travel through it like in a chimney. But still the emitter produces a lot of heat... The black paint really helped. I kind of suspect that three XM-Ls would produce more light with less heat, but I had that LED flying around and didn't really know what to do with it.
I know it's as ugly as it can be, but it works :bigsmile:
