The heat output of the meths burner, to be more correct methylated spirits burner, has been quite low. Just 50W of heat into the boiler with the optimised firebox design.
Adding a steam raising blower increased the heat output of the methylated spirit burner dramatically.
You can see the rate of change in bulk temperature within the boiler is increased significantly when the blower is switched on. This increase is the same for both types of blower: 1. electric fan 2. compressed air jet.
This probably means that both blowers are able to draw more than the required amount of air into the firebox. Hence reaching 100% of the burner capacity.
I updated the cooling curve for the final design of the boiler. As discussed previously the cooling curve for an object is key to understanding the amount of heat that it loses versus it’s temperature above ambient.
This then allowed me to update my simple model of the boiler and so predict the heat input into the boiler. This is shown below for the two blower designs.
For both blower types they were switched on, then off and then on again before finally being switched off. The fan blower was switched off for a longer time than the compressed air blower. In both cases though the heat input to the boiler drops to ~50W when they are off.
The maximum heat input with the blowers on is around 350W and both perform very similarly. However, I now have a number of questions that I need to solve/work through:
- How do I achieve a more controllable heat input to the boiler? Currently I can achieve 50W or 350W.
- What is the efficiency of the methylated spirit burner?
- What is the power requirement of each blower type? Here it would be good establish which is more portable.
Quite a bit more experimentation and modelling is required to optimise the heat output of the meths burner. However, I feel that I have solved the issue of getting heat into the boiler.