Got the block for testing the heat transfer of the tubing made.
I need to figure out how to transfer the heat from the heater while still having around 1 m of tubing inside it and avoid liquids. The easiest way would be to make a cool form, put the the tubing inside a container, add e.g. water and heat it up.
This adds unwanted fluids and more issues regarding daily use. E.g. evaporation, possibility of shorts etc.
But, let's measure and see what happens