Uprading to 3 xhp50 7000lumen

Hi guys
I`m planing to upgrade my 3xml canister dive light to a 3x xhp50 light
The problem is the heat dissipation, because as I built the head it was meant for 3x xml, and dissipation of the heat generated by 3 xml.....

But then I came across the data sheet of both LEDs, and I found that:

cree xml has a termal resistance of 2,5ºC/w
cree xhp50 has a termal resintace of 1,2ºC/w

So If I´m correct the 3x xhp50 should generate less heat than the 3xml?

3 xml (30w) x 2,5ºC = 75ºC (3000lumen)
3 xhp50 (57w) x 1,2ºC = 68,4ºC (7000+lumen):devil:

Can anyone please tell me If I`m correct,
and if I can use the same head for the 3 xhp50 still getting the necessary cooling for the LEDs

Thank you for your replies!!:thumbsup:
M

The thermal resistance of the LED is only a part of the picture as far as temperature.

The thermal resistance of the LED tells you what the difference in temperature will be between the LED die and the back surface of the LED body, per watt of heat generated in the LED.

In addition to that, there are several more interfaces that have thermal resistance: the interface between the LED and the star, the star itself, the interface between the star and the heatsink, and the heatsink itself. All of these interfaces are effectively in series because the same heat has to pass through each one to get from the LED to the water.

The thermal resistance of the LEDs however, is in parallel, since the heat generated by LED A does not go through LED B or LED C. So the thermal resistance of all three is only 1/3 that of a single LED. Also, for every watt of electrical power you put into an LED, you do not generate a watt of heat. A substantial portion of the power comes out as light. With these LEDs, driven moderately to fairly hard, you're probably looking at 30-40% of the power coming out as light. The remainder is converted to heat. For argument's sake, let's say it's 1/3. Then your calculations should look like this:

3 xml - 30W * 2/3 x 2.5/3 C/W = 16.7C difference between die and back of LED
3 XHP - 57W * 2/3 x 1.2/3 C/W = 15.2C difference between die and back of LED

As expected, you would get the same results if you only used one LED:

1 xml - 10W * 2/3 x 2.5 C/W = 16.7C difference between die and back of LED
1 XHP - 19W * 2/3 x 1.2 C/W = 15.2C difference between die and back of LED

Thank you very much!!
You have been very helpfull

So, I`m moving forward with my project!
Regards

Can you keep us updated? Sounds like an awesome project. I might build something similar if it works out