Final Cladding of Small Boiler

Hopefully this is the final cladding of the small boiler. I say that as it is meant to be a test setup. A way of developing my knowledge and skills. However, at the same time this needed to also fulfill my need for it to look good.

inner layers of the final cladding

The boiler cladding consisted of a number of layers. Working from inside to out they are:

  1. Teflon sheet – a thin baking sheet wrap
  2. Medium weight paper wrap
  3. Polythene – this was a thick clear polythene bag
  4. Medium weight paper wrap
  5. Air gap – created using thin wood veneer strips
  6. Bog oak outer layer

The wood veneer was glued to the outer paper wrap (layer 4) with an aliphatic wood glue. The bog oak strips were then glued to the thin veneer and to each other again using aliphatic wood glue.

Why glue? Well, I used this on the original design and after many runs of the boiler it was well and truly fixed together without it being fixed to the copper boiler.

Firstly I placed one strip of bog oak in place and ensured it was absolutely square. Once this was fixed rigid I then had a great stable point to work from. This first stage is worth spending some time over and leaving to cure fully as this is the foundation.

final boiler test setup

Once the boiler cladding was complete I instrumented it as before and ran some tests.

This setup has the final firebox design and the improved meths burner design. I will discuss the final burner design in more detail in another article.

In this image you can also pick out the three thermocouples.

The heat loss of this final design versus temperature above ambient is compared to other test conditions below.

boiler design heat loss

The operating temperature is 140°C and the operating pressure is 40psi. Therefore, we really only need to care about this data point. At this point the heat losses are:

  • Unclad boiler 35W
  • Final design 26W
  • Full cylinder jacket insulation 19W
  • Fully insulated boiler 12W

This comparison of the final design to a fully insulated jacket shows it works rather well. However, I keep wondering if I should have included an aluminium reflective layer?

The final boiler cladding of small boiler actually works rather well. Both in terms of actual data and based on the fact that at operating pressure I can feel the difference in the outer surface temperature compared to my original design.

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