I agree that you want more surface area (fins) near the heat source as this will increase heat transfer through radiation. This slows down and hopefully limits the max temperature of the flashlight.
To sum it up, lots of mass around the heat source helps transfer the heat through conduction (from LED into the metal), then lots of surface area around the heat source helps transfer that heat through radiation (from metal to surrounding air).
Please don’t use an analogy of liquid spreading in zero gravity. This is way off. Liquids, like water, in zero G don’t really spread, the surface tension keeps it together as I’m sure we’ve all seen videos of astronauts playing with water. It’s a bad analogy and may confuse others. It certainly confuses me, at least.
In order to really understand what we are seeing here, we need a cross section view. (I could flip flop the thermal images from these same exterior designs just by manipulating the internal shapes)
Also, where these images taken after the same time frame? I assume so, but want to make sure.
I think one thing to take into consideration is that the above does not solely compare thermal properties of fins between led and reflector vs fins between led and batteries. The two lights are of a slightly different design as well. For example, the fins on the cooler running light are deeper.
I think you’re misunderstanding the picture. The “cooler running” of the light on the left is a BAD thing! For the best performance, the heat should be pouring out of the light, like the one on the right.
This actually depends on the cross section views and how much time has elapsed in these images.
If these shots are after 30 seconds and the light on the left has more mass around the heat source, then it is clearly the better thermal design.
If these shots are after 15 minutes and both lights have the same thermal mass, then the light on the right has the better thermal design.
Thermal imaging shots like this are not the best way to judge a design. They are helpful, but not the best. The LED temperature is the crucial factor and that is not shown here. Whichever light has the cooler running LED of these two images is the better thermal design.
Yes, good summary, ideally a large, high powered light has both, a lot of mass around the heat source and also a lot of surface area.
The analogy is good enough to illustrate where and how fast the heat will flow in the host. I think you might have misunderstood me. You are right that it does not make sense to talk about the distribution of a constant amount of water. But if you place your water source right under the MCPCB and fill up the host (where there would be usually aluminium) then the way the water spreads is similar to the way the heat spreads.
The shelf temperature would be enough (which was also quite a bit lower for the better design). Not without restricting the self thickness or some other awkward design changes. The point of this comparison was to see the performance of two designs with different fin location and the same internal designs. Yes, since it is one thermal analysis. The image displays the equilibrium state of the heat distribution.
The slight changes in design are not relevant for the point, which is that cooling fins right around the shelf improve thermal performance.
No, it is a good thing. The left design is better since the fins are located where there is the biggest amount of heat. That means the temperature at the fins is as high as possible which allows for an as good as possible heat exchange between air and host. The higher the temperature difference between host and air the better the heat exchange works.
I am sorry I caused quite some confusion with the picture. Long story short, there should be fins around the shelf for an optimal thermal performance.
I’ll see if I have a comparison with the two shelf temperatures somewhere floating around, then it should be more clear.
That is something which i have learned different, it is all about area, so more fins (leaving in the middle if they have to be thick or thin) create a larger surface area, so the device can get rid (dissipate) the heat faster.
Left is BAD fin location, right is GOOD fin location:
Left is overall hotter and has a 5 degrees higher shelf temperature:
Same settings and loads and coefficients and time and same everything (well apart from fin location).
Also this comparison only considers the location of the fins.
This would be true if the area very close to the led would be of very high temperature (white in colour); then you would have poor heat sinking, as with a thin screw-on led board.
I was really interested until I realised that this is basically an over driven S70S with a pretty body and a bigger board.
If that’s it then I don’t see why it is worth it.
It looks like it’d just going to get silly hot, have a temperature drop down after 3 minutes which even Thorfire fixed and then its the case of crappy replies.
If I was asking questions to a seller and they started getting shirty with me I’d move along and buy something else. The pre-sale is the chance to show off how amazing you are, how much you care about your customers, how much you know about your product and the time to get to really sell it. If you’re just skipping over questions and saying “wait” whats the point in posting it to begin with.
