My original boiler heat loss test object was a round disc of mild steel and copper. However, this doesn’t relate that well to the actual boiler. This is so that I can test different types of boiler insulation and multi-layer insulation.
My original idea for measuring the thermal insulation for the boiler was to make a heating disc / puck. A bit like a metal ice hockey puck. Different materials could be applied as a disc to the copper surface. I could then measure the cooling rate of the puck.
Effectively I was going to measure the thermal conductivity of different insulation materials. However, this is not a simple process.
Also, look at the puck and you immediately see that the working circular surface is smaller than the rest of the surface area of the puck. This means the insulation of the side and back of the puck will have to be phenomenal.
Working area = 31% of the total area.
Hmmm, I think we have a problem.
The short video gives a great overview of the different thermal conductivity measurement techniques. Also, it gives the pros and cons of each.
After some measurements of the puck surrounded with insulation I abandoned this approach.
This puck took quite some time to make, including silver soldering the copper to the mild steel.
Here you see the parts with flux applied and pieces of easy-flo 55 silver solder just before it was put into the kiln. The kiln being pre-heated to 720°C for the easy-flo 55 to melt and flow through the joint.
Improved Test Object
Now I have moved to something more representative. A 50mm long piece of copper that has been soft soldered to a piece of mild steel bar.
Working area = 58% of the total area.
This is a much better boiler heat loss test object.