Rocket stove mass heater; mass storage

Don't think it will work because the flue gasses have already passed through the heat exchanger so the flue gas temp. leaving the gasser is generally below 400 degrees. Extract any more heat from it and you would likely run into condensation problems imo.

If you look at the numbers that the rocket stove people brag about (IE 100F or lower exhaust temps from the mass) you ARE condensing, no question. I think the original method of using cobb mitigates this in that when the stovepipe rots out, the condensate is absorbed by the cob and neutralized there depending on the soil/ cob composition. what I've never seen from anyone on the rocket stove forums is how many pounds of wood you can run thru the stove per hour or day. I think they're really oversold by their proponents.

they can be a solution for some applications (chicken coop?) but I'm skeptical.

karl

My only experience with gasification is with my EKO 25 which upon close examination has the J tube that the people building the rocket stoves declare as an essential element , the difference being that the EKO uses a fan to enhance the combustion as opposed to a natural draft. As far as condensation is concerned I believe that an insulated chimney and or keeping it inside the envelope as long as possible is key. In his book , Ianto Evans suggest the exhaust exit the side of the building angled slightly down before returning vertical for only a few feet with an 180* bend at top also has a creosote trap were it exits the building. It seems to me if there is any condensation issues it would be in the rocket stove mass and not with the boiler itself. I'm looking forward to barnartist 's further experiments since I too have thought about the prospects of scavenging more energy out an all ready pretty efficient system.

If I'm understanding you correctly you are experiencing condensation upon exiting the building as it hits the cold air, I would believe that to be the norm with the lower exhaust temps. that's why Ianto Evans slants it slightly down at that point with a small hole in the bottom of the 90* angle going vertical. I got to believe that there is a certain amount of condensation in any type of mass heater including masonry heaters that try to extract the max. amount of heat from the exhaust.

I find this an interesting case of getting more heat out of an ordinary wood stove http://www.geopathfinder.com/Masonry-Stove.html

I believe in this scenario it allows you to establish a good fire and warm the chimney before engaging in "heat the mass mode" which should help the chimney to draw.

I'm not following your thought process here, if you're looking for thermal mass and you have a boiler why not store the heat it in water? Cob comes in a poor second when you compare it's heat retention properties to water. I think rocket stoves are a great idea if someone's starting from scratch and they have no money to do anything better but if you've invested in a gasifier you've already moved to a higher plane. To rob any more heat from the flue gas is going to have a negative effect on your boiler operation.