Yesterday i did a very strange, "exciting" test to know this a bit more accurate.
I wired a Cree 2530/ 5000K/ T4 to a 10W @ 300mA led driver.
I wanted to be shure to use a middle class quality chip and run it under low current efficiency.
My wattmeter showed 10,9W / Vf = 32,4V @ 300mA.
All calculations of temp. change and heat energy you can do here:
https://rechneronline.de/chemie-rechner/heat-capacity.php
I wrapped the chip into a waterfilled "ballon" 0,175L and switched the light on.
After 30 min. the temp. rised from 25,4°C to 40,5°C ---> 6,2W during 1800 seconds.
I estimate the power loss for the led driver ~ 0,5W
So 10,9W(powermeter) - 0,5W(led-driver) - 6,2W(heat energy) leaves 4,2W for the light.
Light efficiency is 38,5%.
Today i repeated the same test, but only 20 min. - I wanted to know more about the heat loss
or heat transfer to the ambient.
After 20 min. the temp. rised from 28,4°C to 38°C --->5,9W during1200 seconds.
Following the water temp. of the ballon cooling down in the room i measured 9 min.
to take the temp. down from 33,7°C to 32,7°C. ---> 1,2W / 9min. = 2,6W / 20min.
This must be more or less my average heat transfer loss to the ambient and is bigger than i thought. You have to add it to the bill.
UUUUOUPS - that`s bad for light efficiency.
New calculation is: 10,9W total - 0,5W led driver - 8,5W heat energy --->
my light efficiency is just 26,6%.
Any coments and critic is welcome - on the pics you see simple things for the measurement,
that you can find in smart lighted household.
I would like to see many results from different chips - with different spectrum and power.
Can anybody help me please !