Basically water flows through a copper tube that's wrapped around (or inside) the exhaust of a rocket stove, getting heated in the process. Since the water tank is indoors, it would be at or slightly below room temperature (not less than 10C/50F). Do you think there would be enough heat in the exhaust to heat the water to 50C/125F?
There is no thermal mass to siphon off the heat up to that point and, if needed, insulation can be placed on the vertical exhaust to reduce heat loss before the copper pipe.
I suppose it would be more efficient to place the copper tube lower on the exhaust, but having it come out up there makes for easy gravity feeding of warm water to where it's needed.
Also, can the exhaust of a rocket stove go out horizontally through the wall like that?
Hello Big Al! Thanks for the welcome and the detailed reply I have a clearer picture now and the dangers involved.
I forgot to mention/draw that the stove would have thermal mass (bricks and cob) around it. Actually a variation of this stove already exists (outdoors) and this is where I got the idea to heat water in an indoor system. The exhaust on it is warm, but not hot so I was "worried" about it not being enough to heat water... but I suppose I should point my worries in the opposite direction for an indoor system
Unfortunately solar water heating won't cut it in the winter, so we'll have to stick to wood or propane. Still, there's about a year to go before we attempt this and we'll be building another RMH in the meantime... so there will be a lot of experimenting and learning in the meantime. Living in the age of infrared thermometers certainly makes this process a little safer
My rocket sauna stove is set up almost exactly as you show in your diagram, so far it works well for me! I briefly experimented with a copper coil on the exhaust for heating water, but without success. I had hoped to have it work as a thermal siphon in bucket on the floor. When my stove is running very hot (heating the room to 200F+), the 6 inch diameter exhaust pipe can be quickly touched without getting burned.
That is a really big piece of pie for such a tiny ad: