Titanium vs Aluminum Thermally (IR Images)

[cmacclel]

After looking at these images is quite clear to see how much better Aluminum (6061) is at transferring / dissapating heat over Titanium (6al-4v). Pay no attention to the Temp in the upper left hand corner as that only represents the temperature at the crosshairs.









Thermal Images of Aluminum (Top) and Titanium (Bottom) Lights at Various Drive Levels using an SST-50 LED


Thermal Images at 2500ma Drive Level

Base / 1 Minute / 2 Minutes

3 Minutes / 4 Minutes

Thermal Images at 1000ma Drive Level

Base / 1 Minute / 2 Minutes

3 Minutes / 4 Minutes / 5 Minutes

6 Minutes / 7 Minutes / 8 Minutes

9 Minutes / 10 Minutes / 11 Minutes

12 Minutes

 

[gadget_lover]

What's your interpretation of those results?

Which did better at getting rid of heat?


Daniel

 

[cmacclel]

What's your interpretation of those results?

Which did better at getting rid of heat?


Daniel

The Aluminum transferred the heat to the whole body where as 90% of the heat stayed right where the heatsink is on the Titanium light. Also the aluminum light showed 20f+ cooler throughout the test.

 

[Ajay]

Thank you cmacclel

Excellent work, results clear as day.

 

[65535]

I realize these things are quite accurate. What about the difference emissivity of the surfaces? Obviously it gets the point across aluminum transfers heat far better. Just curious if the different emissivity can cause inconsistencies in the readings on a FLIR camera.

 

[cmacclel]

I realize these things are quite accurate. What about the difference emissivity of the surfaces? Obviously it gets the point across aluminum transfers heat far better. Just curious if the different emissivity can cause inconsistencies in the readings on a FLIR camera.

Both lights where covered with kapton tape so there should be no difference in emissivity.

Mac

 

[dudu84]

At first I thought those images came from CFD simulations, very cool :thumbsup:

This answered heat-related questions about my Ti lights, Thanks a bunch! :goodjob:

 

[easilyled]

These pictures are very conclusive that Al. has far superior thermal conductivity to Ti.

Of course to drive a small light at 2500ma for any sustained length of time is inadvisable, particularly for Ti.

It would be interesting to see for Ti only, the comparison between this small light and a much bigger one (eg. your 1D Mag-sized Ti lights with SST-50),
to see if the greater bulk and volume makes it safer to drive the light at this sort of current level for longer.

 

[hydrou]

Just to add some numbers.

Electrical conductivity of Al: 37.7 * 10^6 A/(V*m)
Electrical conductivity of Ti: 2.5 * 10^6 A/(V*m)

Thermal conductivity of Al: 235 W /(K*m)
Thermal conductivity of Ti: 22 W /(K*m)

So, one can see easily, that there is a factor of more than ten between thermal as well as electrical conductivity between the pure substances. And higher values indicate a way better conduction of heat or current resulting in less hot spots or thermal problems.

And just for comparison pure Fe:
Electrical conductivity of Fe: 1.0 * 10^6 A/(V*m)
Thermal conductivity of Fe: 80 W /(K*m)

In general, alloys might have slight changes to these values, but the order of magnitude will not change.

 

[karlthev]

Thanks Mac--great piece of data here!


Karl

 

[EngrPaul]

Thanks for the post!

This is exactly what I would expect to see. The average outside temperature of both flashlights is the same, but the local temperature of the titanium light is higher near the emitter heat source.

What onlookers should take away: If the temperature is this much higher on the surface near the emitter, imagine how much hotter the emitter is inside. Higher emitter temperature = dimmer LED, both now and over time.

Would it be possible to measure relative output over the same duration as the tests above? I bet the output of the titanium light would sag due to emitter temperature rising more quickly.

 

[tino_ale]

Would it be possible to aim the IR camera directly towards the emitters and read the actual die temperature?

These tests are very interresting and well done. Clearly the heat is better spread throughout the Al body. The Al body tail is hotter than the Ti tail.

Still IMO the only test to get a definite quantitative answer to how good Al and Ti are relative to each other would be to measure actual junction or at least emitter temperature (not just heatsink or body temperature) while both lights sitting on a table and repeat the test with both lights held in your hand. This very last measurement is in fact the only one I am interested in but unfortunately it doesn't seem easy to set up.

I guess a IR camera equipped with a macro lens could measure the phosphor temperature?

 

[KowShak]

I've a few questions....

Aside from the material, are the two lights identical in terms of dimensions / material thickness etc? Assuming that they are, the conclusion here is simple, TI is not as good a material for LED lights as aluminium is.

Do you think the difference would be as marked if the wall thicknesses were thicker / thinner?

 

[cmacclel]

Would it be possible to aim the IR camera directly towards the emitters and read the actual die temperature?

These tests are very interresting and well done. Clearly the heat is better spread throughout the Al body. The Al body tail is hotter than the Ti tail.

Still IMO the only test to get a definite quantitative answer to how good Al and Ti are relative to each other would be to measure actual junction or at least emitter temperature (not just heatsink or body temperature) while both lights sitting on a table and repeat the test with both lights held in your hand. This very last measurement is in fact the only one I am interested in but unfortunately it doesn't seem easy to set up.

I guess a IR camera equipped with a macro lens could measure the phosphor temperature?

Tino your exactly right. The problem is when a light is assembled it is difficult to measure to measure the heatsink temp. as close as possible to the die unless you drill holes into the light This was a quick and dirty simple test. I hope to set another test up tonight with a thermal coupling into the heatsink as close as possible to the LED. I will then re-run the same test with the same heatsink / LED in both bodies.

 

[cmacclel]

I've a few questions....

Aside from the material, are the two lights identical in terms of dimensions / material thickness etc? Assuming that they are, the conclusion here is simple, TI is not as good a material for LED lights as aluminium is.

Do you think the difference would be as marked if the wall thicknesses were thicker / thinner?

The lights are exactly the same just different body material.

Mac

 

[cmacclel]

These pictures are very conclusive that Al. has far superior thermal conductivity to Ti.

Of course to drive a small light at 2500ma for any sustained length of time is inadvisable, particularly for Ti.

It would be interesting to see for Ti only, the comparison between this small light and a much bigger one (eg. your 1D Mag-sized Ti lights with SST-50),
to see if the greater bulk and volume makes it safer to drive the light at this sort of current level for longer.

Daniel I doubt it matters much the thickness or the size of the Titanium. The fact is it does not have good thermal properties so the heat stays in one general area.

Though like you said it would be ridiculous to expect a light of this size to sustain 10 watts to the emitter. The 2500ma level is basically a burst mode and should not be used for more than a couple minutes.

Mac




Mac

 

[hydrou]

@tino_ale:

I am afraid it will be not that easy... On the one hand, the lenses used for theses types of cameras ususally do not work with normal glass. You will need special lenses built with special optics. And on the other hand, you need to know the so called emissivity of the object. This will vary between 0 for an ideal white body and 1 for an ideal black body. Therefore, it is not possible to calculate exact temperature values for surfaces with unknown composition or radiation properties.

 

[Fulgeo]

Daniel I doubt it matters much the thickness or the size of the Titanium. The fact is it does not have good thermal properties so the heat stays in one general area.

Great stuff Mac. I found these images very informative and interesting. One thought thou which you probably already thought of, it seems that some of the short comings of the thermal properties of Titanium could be resolved with finning. Your images really do point to where the problem is. Maybe a few cooling fins cut into the head right where the heat is could make a difference? Also because the Titanium is so much stronger than Aluminum maybe you could make circular long horizontal thin fins. I know that thermal mass is important but maybe with Titanium less is better where there is heat? Anyway you have the tools to play and I am envious. Thanks for sharing.

 

[MrGman]

The differences in emissivity aren't going to be that great and in this comparison really doesn't mean much because the Titanium body showing the lack of transfer from head to tail across itself is the real issue. The Titanium body doesn't change in emissivity across itself and its not transfering the heat as well as it could plus we see the thermal transfer numbers published. This series of thermal graph points out something that should be stated to make it very obvious. Titanium body high power flashlights are a contradiction of purposes. They cost more money for the exotic materials but they are 10 times less effective in transferring the heat away from the LED/heatsink in the head which is what you don't want to do. So people pay more money for the exotic metal because its "cool" and may not scratch as easily yet its far less effective in thermal management for the high power flashlight they are buying then the Aluminum that is much cheaper in cost. If these were incandescent lights we wouldn't care but for an LED, especially the higher power ones, running more than 10 watts of power, Titanium alloy hosts are the wrong way to go if you want the best possible thermal transfer to keep the LED from overheating. Truth is Truth. Thanks to cmacclel it is now abundantly clear we shouldn't be wasting money on the expensive Titaniun flashlights in the high power units such as an SST-50 or 90 because it hurts thermal transfer and the LED may not last as long with continued use. ouch

 

[cmacclel]

MrGman I agree with you

But

"It Don't Mean a Thing If It Ain't Got That BLING"

But seriously Titanium lights are completely usable at lower drive levels. As for the SST-50 even driven at 150ma as in this particular light on level one it produces plenty of light. The burst mode must be used with common sense




Mac