3 ms·

> Mostly I’m surprised it’s that easy; I would have thought anything that can radiate heat slowly and consistently would by necessity also absorb heat slowly an

> Mostly I’m surprised it’s that easy; I would have thought anything that can radiate heat slowly and consistently would by necessity also absorb heat slowly and consistently, making it difficult to capture most of the heat from a fast-burning stove. My understanding is that this is the motivating principle for the "bell" part of a rocket stove masonry heater. The hot exhaust from the combustion chamber is piped into a massively larger enclosed airspace, which has an exhaust port at the very bottom. Since hot air rises and cool air falls, most of the heat in the exhaust will be absorbed by the bell enclosure before finally being vented through the exhaust port. By enclosing the bell in masonry, it meets the design restrictions you mention. I think it's also possible to build a masonry heater without using rocket stove principles, just a fireplace with a huge mass of masonry surrounding it. In that case, you'd want cladding with somewhat high thermal conductivity to capture the exhaust heat, but it's thick enough that the solution to the Fourier heat equation [0] is low enough to meet the design restrictions. [0] https://en.wikipedia.org/wiki/Heat_equation#Heat_flow_in_a_uniform_rod https://en.wikipedia.org/wiki/Heat_equation#Heat_flow_in_a_u...

tharkun__ 4y ago
Funny how we have a post here from some company selling these and it feels like the thought is "this is new". In fact it's how people have heated for a very very long time. Lots of these in European houses from days past. And in fact I know a guy in Germany that heats his living room, dining room and kitchen with one that's built into the wall between these three rooms. Not as fancy as what you see there or on Wikipedia. Just tiled wall basically. Old house and instead of ripping it out when he bought it, he cleaned it up and uses it to heat. A kachelofen uses a maze-like passage created out of firebrick to release gases and smoke from the wood fire slowly, allowing the firebrick to retain as much heat as possible from the gases and smoke. The ceramic tile surrounding the stove also acts as insulation to retain heat. Such stoves were carefully designed so that the minimum amount of heat would escape, only as much as needed to warm the flue to maintain a proper air draught. The firebrick used in the construction holds 80% more heat than ferrous metals such as cast iron, while its heat conductivity is 1/45 that of iron or steel: A kachelofen is efficient enough to warm a house for up to 6 to 12 hours after the fire has stopped burning https://en.m.wikipedia.org/wiki/Masonry_heater https://en.m.wikipedia.org/wiki/Masonry_heater
- vram22 4y ago
  >Funny how we have a post here from some company selling these and it feels like the thought is "this is new". Yes. Related: Russian stove: https://en.m.wikipedia.org/wiki/Russian_stove https://en.m.wikipedia.org/wiki/Russian_stove And this article show that many of these variants are related, and that the basic principle is very old, even prehistoric: https://en.m.wikipedia.org/wiki/Masonry_heater https://en.m.wikipedia.org/wiki/Masonry_heater
- jacquesm 4y ago
  You can find these all over Poland and many other Eastern European countries in older houses.
- orthoxerox 4y ago
  I think the whole novelty is not the masonry heater part, but the rocket stove part, which helps you burn as much carbon in your firewood as possible.
- Xylakant 4y ago
  The novelty is indeed the bell combined with the rocket stove. A classic old Kachelofen restricts the airflow since the channels that the fire fades are routed through are long and often small. This construction achieves the same effect of capturing almost all of the heat from the fire, but does not restrict airflow. Better airflow leads to a better combustion. It’s a pretty ingenious modification of a known concept. As far as I can tell, this is indeed new.

tharkun__ 4y ago

Funny how we have a post here from some company selling these and it feels like the thought is "this is new". In fact it's how people have heated for a very very long time. Lots of these in European houses from days past. And in fact I know a guy in Germany that heats his living room, dining room and kitchen with one that's built into the wall between these three rooms. Not as fancy as what you see there or on Wikipedia. Just tiled wall basically. Old house and instead of ripping it out when he bought it, he cleaned it up and uses it to heat. A kachelofen uses a maze-like passage created out of firebrick to release gases and smoke from the wood fire slowly, allowing the firebrick to retain as much heat as possible from the gases and smoke. The ceramic tile surrounding the stove also acts as insulation to retain heat. Such stoves were carefully designed so that the minimum amount of heat would escape, only as much as needed to warm the flue to maintain a proper air draught. The firebrick used in the construction holds 80% more heat than ferrous metals such as cast iron, while its heat conductivity is 1/45 that of iron or steel: A kachelofen is efficient enough to warm a house for up to 6 to 12 hours after the fire has stopped burning https://en.m.wikipedia.org/wiki/Masonry_heater https://en.m.wikipedia.org/wiki/Masonry_heater

vram22 4y ago
>Funny how we have a post here from some company selling these and it feels like the thought is "this is new". Yes. Related: Russian stove: https://en.m.wikipedia.org/wiki/Russian_stove https://en.m.wikipedia.org/wiki/Russian_stove And this article show that many of these variants are related, and that the basic principle is very old, even prehistoric: https://en.m.wikipedia.org/wiki/Masonry_heater https://en.m.wikipedia.org/wiki/Masonry_heater
jacquesm 4y ago
You can find these all over Poland and many other Eastern European countries in older houses.
orthoxerox 4y ago
I think the whole novelty is not the masonry heater part, but the rocket stove part, which helps you burn as much carbon in your firewood as possible.
Xylakant 4y ago
The novelty is indeed the bell combined with the rocket stove. A classic old Kachelofen restricts the airflow since the channels that the fire fades are routed through are long and often small. This construction achieves the same effect of capturing almost all of the heat from the fire, but does not restrict airflow. Better airflow leads to a better combustion. It’s a pretty ingenious modification of a known concept. As far as I can tell, this is indeed new.