Okay guys, I'll start with a quick introduction, I've been interested in rocket stoves/ rocket mass heaters for a number of years, and google yields a lot of results from this site, so I figured it's time to join and ask the experts for some input prior to attempting my first heater.
I part time off grid, I've build a wood barrel sauna next to the river, and next I'd like to add a plunge tank. I've got a couple IBC totes I received for free and I'm willing to cut one up to make a plunge tank.
My issues being off grid, is keeping it from freezing.
Design: what I'm thinking is build a self feeding rocket heater housed within a propane tank or similar metal vessel, but really, it will be whatever is cheap and available, so I'm leaning towards that. Of course I'll take all necessary precautions prior to cutting or welding.
I know it's mentioned that metal for the burn chamber is subject to extreme temperature will burn through eventually and isn't ideal, and should properly be insulated by fire brick or clay. Unfortunately I don't think that will be possible inside a propane tank due to its size. So perhaps adding metal plates surrounding the burn chamber might buy it some time? It also won't be running daily, the intentions are only to keep the IBC tote from freezing, so maybe weekly burns, or maybe the odd extended burn to get he water up to hot tub temperature, if it's even possible. Again, primary goal is to keep the water from freezing, and it would be a bonus if I could get it to hit tub temperatures!
I would like to have the burn chamber and riser within the propane tank, and the heat pass around the outside of the riser and exhaust out a chimney from the side of the bottom of the tank.
So up until this point this heater would work above water, what I'm proposing is to have the angled feed tube extend through the side of the IBC tote by means of a gasketed metal flange bolted in place that surrounds the feed tube as well as ash clean out/ air feed. Hopefully the water in contact with the metal "flange" coupled with some distance until the plastic tote would prevent it from ever melting. And of course have the chimney from the unit extend above the water line.
What in hoping this would accomplish by having the top of the heat riser submerged, with a jacket around it before passing exhaust is to extract the maximum amount of heat from the fire while also keeping the burn chamber and heat riser hot (as opposed to the water pulling heat directly from an unjacketed heater such as a commercialy available hot tub snorkel stove).
By means of the gasket and bolts, the entire heater could be removed from a drained tank come time when the burn chamber burns through, or should a weld spring a leak and flood the entire system and require re welding.
This design would also allow the heater to be positioned at the bottom of the IBC tote and housed under a wooden bench, heating cooler water and theoretically allowing for more volume of water above the heater to be warmed up, addressing an issue I've found with my parents snorkel stove hot tub.
What do you all think about this proposed design?
Anything I've overclocked?
Can't wait to hear your valued input,