Though I am a newbie to this forum and have not yet built my own RMH (still researching things but building some brick style RMH toys in the back yard first LOL) I do have some thermal dynamic background and experience. I am not only impressed with your system and innovation but also your technical skills. Adding to the statements of others, "WELL DONE"
I had a thought about the insufficient water for your cooling that might allow for a passive continuous (for the most part) water supply cooling system vice an active (pump) style. This would be beneficial for those off the grid that have a technical mindset and enjoy tinkering on things.
If you extended the length of the cooling insert, possibly with a modification to the feed tube using fire brick or just making the length longer while maintaining the proper horizontal access port clearances, a copper pipe water coil could be wrapped around the extruding section of the insert and could be connected to an external tank of cooling fluid. A thermal siphon effect would drive the water and promote flow back to the tank. The extruding feed tube could also have cooling fins attached where the copper tube heat exchange pipe could go through these fins and the overall amount of heat transferred could be modified for optimal performance.
This could actually be designed to allow the water to boil off safely to an outside area through an additional heat exchanger to capture this heat for other purposes (perhaps a hot water tank preheater??) in a safe manner. This would allow the additional latent heat to be removed gaining additional cooling value while the steam condensation through the heat exchanger would provide additional heat input to the hot water pre heating system too. In a power plant this would be similar to creating a combined cycle design which captures the waste heat and gets useful work out of it.
A further enhancement would be in using this very low pressure steam to heat an additional radiator to capture this heat prior to exhausting outside for even more efficiency and comfort. The exhaust steam could even drive a small fan for those with the technical know how but would not be required for the system to work.
Of course proper safety precautions would need to be placed within the system(s) but the external water storage tank could be much larger and I believe that the system would even be safe if the water tank was not refilled and went dry. At the minimum, the impact of having a much longer time frame of your cooling water should allow for a sufficient amount of burn time for most of the RMH's I have seen discussed on this forum. In addition, the additional heat transfer area from the tube modifications along with the impact of additional air flow heat exchange everything above the feed tube will improve the cooling of the feed tube by itself even when the water system might boil dry.
Based on what I have read, copper tubes should be able to handle the temperatures you mentioned even when dry. Subsequent filling of a dry water tank and the copper tubing should be done after the system has cooled off of course.
Most items listed could be obtained at little to no additional cost for the frugal minded (like myself LOL).
I would be interested in your thoughts and those of others who are willing to evaluate and hopefully improve on this idea. I would like to eventually build a prototype with all of this, but for now time constraints make this just an idea to pass along. If anyone picks up on this idea and builds it please let us all know your results.
Hope to hear from others soon
Tom<>
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