Convection heat transfer from the LED strip

In past experiments, i noticed the LED chips temperature on the chipboard compared to the LED chips temperature in air. This temperature was higher! This seemed strange to us, because the thermal conductivity of air is much lower than the thermal conductivity of chipboard. The heat should go into the chipboard better than into the air.

Where did i go wrong? How does the heat from the LED strip dissipate the air?

Data from past experiments:
1. LED strip chip temperature, suspended in the air.
2. LED strip chip temperature, glued to the aluminum profile and suspended in the air.
3. LED strip chip temperature on chipboard.
4. LED strip chip temperature, glued to the aluminum profile on the chipboard.

In many cases, the LED chip temperature has increased on the chipboard, not decreased.

I think the clue is in the movement of air near the LEDs (heat sources), not in the thermal conductivity of the air.
The effect of convection - warm air moves up, and cold air moves down. The air is heated by the LED chip and moves upwards, taking the heat away. In its place comes the cold air, which heats up and goes up.
So the heat from the chips goes into the permanently cold air, effectively taking that heat away.

Measurement description

To confirm this theory, i will modify the test bench from the previous parts of the experiment (learn more) .

I will add a thick layer of extruded polystyrene (XPS).
I will create an obstacle for the rise of warm air from the LEDs in the form of an extended flat surface. I use XPS because this excellent material has a very low thermal conductivity. Therefore, it will not be a heat sink for the LED strip base. I investigate only the air movement.

Test bench and measuring instruments

The measuring instruments and the other things were the same as in the last experiment (learn more).

Measurement results of LED strip chip temperatures on XPS

Thermal images. LED chips on the XPS

‍