Hi All. I’ve been thinking pretty hard about how to get the next level of cooling for people who really push the lumens and thus, heat like Dale.
Heat pipes are outstanding at carrying heat from where we don’t want it to somewhere else. I just need to figure out an elegant implementation that doesn’t adversely change light dimensions too much.
Your thoughts? Dimensions are L=3.15, D=.158” (80mmx4mm)
Here is a render of a 1 inch pill with a cavity for a 17mm driver. You can see that even at 3.15” long the length of the heat pipes is problematic. They have to be connected to a metal mass (preferably soldered). They can be carefully bent, but I am unsure what kind of radius would be ok.
Small lights are really tough to do anything with. Everything that can be done to aid heat sinking or cooling makes them bigger. Then they are no longer small enough to be called EDC.
I will look for a very small fan though and see what I can come up with.
What if you can have several heat pipes wrapped around themselves to form the battery tube, I think it might be even better, maybe someone with a metal 3D printer could do it.
Something like this but the tubes welded together or 3D printed together to be waterproof.
I have had similar musings on this concept. I think that the heat pipes will work. The problem is where does the heat go. If the pipes are housed in the body of the light then you just cook the battery. If you run the pipes to the outside of the light body then the blood circulating through your hand can pull the heat away. I fear that the heat will be too hot too handle. Only one way to find out.
If I recall right, you need to “size” the heat-pipe to the expected hot temperature side, and expected cold temperature side, for them to be efficient.
Too hot, and all the carrier-fluid just boils off and stays a vapor, and too cool, and nothing happens. Ie, you need the carrier fluid to have the “correct” boiling-point so that it’ll start boiling off when the hot side gets “too hot”, and condense on the cool(-enough) side to dump the heat.
I’ve been thinking about it as well.
I think that the best use would be to make a custom vapor chamber to replace the shelf. Very thin yet very potent….
Not sure how feasible is that though.
If that works, a higher-end choice would be a 2-layer head with a chamber extending all the way from the shelf to near-bezel.
As to making a tube from a folded pipe…you make the vapor path very long this way. Multiple parallel pipes would work way better.
Wrap it around the outside, like the hand protection “bail” used on swords.
That way it will protect the battery from heat and still serve as a hand-warmer.
The problem is that a small light would have to be significantly bigger to fit heatpipes on the inside of the body tube.
It would increase the diameter of the light by 5-10mm.
A large flashlight that would fit them easily and benefit more from the extra cooling would also be pumping out a lot of heat, and that would be uncomfortable to hold.
I think it would only be good to use in a flashlight that has a handle where you’re not actually holding the body tube and it would be ok for that to get hot.
Batteries also perform better at hotter temperatures so as long as the body tube isn’t getting to like 60+ degrees it would be ok.
Guiding heat away with heat pipes, to be transferred to the air elsewhere in the flashlight could make different designs possible but it will never win from a short thick heat path made of aluminium or copper to fins close to the led in the flashlight head.
We keep using the bottom half of the host, from LED down. What about from LED up? Thick reflectors with mass on mass interface to the pill. Those heat pipes instead of down go up. Interface to the reflector and even better interface to the fins that often are so high there more decoration than function.
You have me envisioning a handheld super-bright light with lots of emitters, with water cooling via rubber pipe to a giant heatsink and fan setup rigged with backpack straps. Sorta like those things from Ghostbusters… :person_facepalming:
most flashlights don’t use from LED up because the fins would add diameter to an already large diameter head. It is much nicer to have the fins on the lower part of the head where the fin diameter can make up for the body diameter.
2) making reflectors thicker would overcomplicate things. Most of the pill is already covered by the LED MCPCB anyway, and the top of that is covered in an insulating layer, it is not bare copper.
You can simply make the metal of the head thicker to conduct the heat upwards, as seen here:
3) the distance between the LED shelf and the top of the head is too short. You need a large area on either end of the heatpipe first, one for hot and one for cold, then you have the distance between them where they effectively transfer the heat.
This means that the heatpipe needs to be at least several inches long, and if you want a significantly higher heat transfer than just using solid copper it should be quite long with enough area on either end, so maybe 6-12 inches.
This is why it could be useful to transfer the heat to the body tube, but it would be basically useless to move the heat a couple inches to the top of the head.
Oddly enough, I have considered casting an aluminum body (yes, I built a foundry) that could accept heat pipes through cavities. I think the ideal solution would be to sink the heat to the tail cap and body at that end.
There are a few problems with this:
Molds are expensive to make
Time consuming to do revisions
Bulkier than a round battery tube
Aside from being able to run heat pipes, there is one very obvious upside. I could shape it however I wanted.
I am looking into this as well. I was thinking of bringing the heat pipe outside of the body and bending it back around to nest in the fins of the head. As far as reflectors transferring heat. I think that is a reality in some lights already. There is a limit as to how much can be conducted though, since most reflectors have thin walls somewhere along the way.
