Post by hanee on Nov 15, 2018 6:30:46 GMT -8
Hi there, hoping that Matt or someone who knows about his riserless core design could answer this question:
We're trying to design (and/or use existing plans) an appropriate cooking/heating rocket for a 192sqft building. Our heating needs will vary from 48-96kbtu total for the day. (Roughly 2000BTU/hr(0.6kw) - 4000BTU(1.2kw) mean output across a day.)
Our rough estimated cooking portion of that is approximately 3650btu per meal (3x a day), based on our current propane usage.
We're looking at the Tiny Masonry Cook Stove by matthewwalker as well as just designing our own off of peterberg's plans on batchrocket.eu (or possibly a J-tube), but something is not adding up:
Peter's site (http://batchrocket.eu/en/building#size), gives a sizing for a 6" system as generating 0.95kw mean daily output per burn on a full load. He also seems to indicate efficiency will go down if burns exceed twice a day, or if a partial load is burned. All of this information seems to indicate that if you wanted to fire 2-3x a day (due to cooking needs) in our building, you'd want 0.3-0.4 mean daily kw per burn -- which would mean a 4" or smaller system size. And even at 4" you'd probably have to do less efficient partial burns much of the spring/fall to avoid overheating.
Meanwhile, in one of Matt's videos, he seems to be saying he's put a load in every 2.5 hours during a morning, in a 6" system. It's a little unclear how much wood is going into that stove (in the examples he has it is fully loaded though), and perhaps the burn box is smaller than a normal 6" system, but in any event, if he is burning at 80 or 90% efficiency, and loading it 3x, he should have already generated a mean power of 2.85kw in a single morning. Even if his burn box were half-sized, he'd have generated more heat than we need.
In posts on this forum and on his site he describes the difference between the riserless core and a normal batch box being a "longer burn profile", indicating that it would burn the same quantity of wood a little slower at a similar (but maybe slightly lower) efficiency. So less BTU/hr (and I assume combustion temp) during combustion phase. That's the only information I've found as far as understanding the properties of the core. But I'm completely confused as to how the rate at which fuel burns would have any effect on the total fuel burned, given the same (or roughly the same) efficiency as any other well designed rocket core. My understanding would be that his house is either extremely hot or he's putting extremely little fuel into the stove or his efficiency is low, none of which seem to be true based on the videos or his recommendations that the system would suit a 200sqft tiny house.
Can Matt or anyone else shed some light on heat load sizing and the riserless core (or suggest alternate design options)?
We're trying to design (and/or use existing plans) an appropriate cooking/heating rocket for a 192sqft building. Our heating needs will vary from 48-96kbtu total for the day. (Roughly 2000BTU/hr(0.6kw) - 4000BTU(1.2kw) mean output across a day.)
Our rough estimated cooking portion of that is approximately 3650btu per meal (3x a day), based on our current propane usage.
We're looking at the Tiny Masonry Cook Stove by matthewwalker as well as just designing our own off of peterberg's plans on batchrocket.eu (or possibly a J-tube), but something is not adding up:
Peter's site (http://batchrocket.eu/en/building#size), gives a sizing for a 6" system as generating 0.95kw mean daily output per burn on a full load. He also seems to indicate efficiency will go down if burns exceed twice a day, or if a partial load is burned. All of this information seems to indicate that if you wanted to fire 2-3x a day (due to cooking needs) in our building, you'd want 0.3-0.4 mean daily kw per burn -- which would mean a 4" or smaller system size. And even at 4" you'd probably have to do less efficient partial burns much of the spring/fall to avoid overheating.
Meanwhile, in one of Matt's videos, he seems to be saying he's put a load in every 2.5 hours during a morning, in a 6" system. It's a little unclear how much wood is going into that stove (in the examples he has it is fully loaded though), and perhaps the burn box is smaller than a normal 6" system, but in any event, if he is burning at 80 or 90% efficiency, and loading it 3x, he should have already generated a mean power of 2.85kw in a single morning. Even if his burn box were half-sized, he'd have generated more heat than we need.
In posts on this forum and on his site he describes the difference between the riserless core and a normal batch box being a "longer burn profile", indicating that it would burn the same quantity of wood a little slower at a similar (but maybe slightly lower) efficiency. So less BTU/hr (and I assume combustion temp) during combustion phase. That's the only information I've found as far as understanding the properties of the core. But I'm completely confused as to how the rate at which fuel burns would have any effect on the total fuel burned, given the same (or roughly the same) efficiency as any other well designed rocket core. My understanding would be that his house is either extremely hot or he's putting extremely little fuel into the stove or his efficiency is low, none of which seem to be true based on the videos or his recommendations that the system would suit a 200sqft tiny house.
Can Matt or anyone else shed some light on heat load sizing and the riserless core (or suggest alternate design options)?