[HN Gopher] Masonry Heaters: 18-24 hours of heat output from a s... ___________________________________________________________________ Masonry Heaters: 18-24 hours of heat output from a single wood fire Author : gjsman-1000 Score : 26 points Date : 2023-02-25 18:57 UTC (4 hours ago) (HTM) web link (www.mha-net.org) (TXT) w3m dump (www.mha-net.org) | macmac wrote: | Malwarebytes flags this site as having a Trojan. | gjsman-1000 wrote: | Well, then it's wrong. | | https://www.virustotal.com/gui/url/3d43fe6f2a5b96525b5b76817... | sp332 wrote: | It's also blocked by Plume routers, but it's not categorized as | anything specific. | devwastaken wrote: | 3rd party AV is useless in modern computing. Ublock origin and | knowing your file extensions is a significantly better | solution. | skybrian wrote: | The electric version of this is called "electric thermal storage" | where the electric heater is used off-peak to heat up ceramic | bricks. It seems unlikely to beat a heat pump, though. Could they | be combined? | world2vec wrote: | My parents have a fire stove like those ones in their house, | built almost 30 years ago. Not a common design in the country | they live but apparently it is in Switzerland where they worked | for many years before. Very efficient indeed. | Dma54rhs wrote: | This is also common and very old tech in all the colder | countries in Eastern Europe but obviously electricity has taken | over. I'm even a bit surprised because I'm having a hard time | thinking how else would you hear your house but probably it's | enough in milder climates to not store the energy like that. | thriftwy wrote: | Did they just invent a Russian stove? | | https://en.m.wikipedia.org/wiki/Russian_stove | | Now when the end game is known, perhaps it is better to just | adopt the existing designs instead of trying to perfect the | current product. | twawaaay wrote: | I built one with my father when I was a kid. | | It was dual purpose cooking range and a huge mass of bricks for | heat capacity. It was built at the spot where multiple walls met | in the centre of the house to increase mass of bricks in contact | and to heat multiple adjacent rooms. The walls in those rooms | would typically be too hot to touch. | | One weakness of our setup was that it would suck the air out of | the house through the night. Another was that complex internal | tunnels made the maintenance difficult. | | If I built one today I would make sure to fix it and create a | sort of heat exchanger for coming air. | ghaff wrote: | It's an interesting idea although I assume it has to be somewhat | baked into new house/addition construction. | | A big downside of conventional wood stoves I find is that, if I'm | not going to be hanging out at home--mostly around where the fire | is--for the day it's not really worth it a lot of the time. I | fire up my wood stove mostly when it's especially cold and I'm | not primarily working in my office. | pjkundert wrote: | If you want a lot of background on designing and building an | effective "rocket stove" (the core of a masonry heater), you'll | enjoy this: | | https://batchrocket.eu/en/building | mmastrac wrote: | I vaguely recall seeing a YouTube video about some folks living | in Siberia and using these to keep their homes warm. | fwlr wrote: | You have to follow a few links to get to a definition of what | masonry heaters actually are, but it ends up at https://www.mha- | net.org/docs/def-mha.htm | | Specifically the important parts: "a mass of at least 800 kg. | (1760 lbs.)", "an overall average wall thickness not exceeding | 250 mm (10 in.)", "external surface of the masonry heater ... | does not exceed 110 C. (230 F.)", "at least one 180 degree change | in flow direction" of the released gas. | | Essentially, it's a rocket stove and a large thermal mass of | masonry, and the masonry has a few design restrictions to meet | certain performance characteristics (i.e. it should absorb most | of the heat released by the stove and it shouldn't release that | heat too quickly from any particular point on the mass). 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. | a9h74j wrote: | > I would have thought anything that can radiate heat slowly | and consistently would by necessity also absorb heat slowly and | consistently | | Something like a ratio of flame-side heat absorption at flame | temperatures, to room-side emissivity at room-side | temperatures(wavelengths)?? This could fall out from material | properties without appearing as an explicit design detail (e.g. | a surface treatment). | bcbrown wrote: | > 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 the stove. 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. | | https://en.wikipedia.org/wiki/Heat_equation#Heat_flow_in_a_u... | Tcepsa wrote: | TL;DR different modes of thermal transfer can transfer heat at | different rates. | | There are a couple factors at play that help it absorb heat | faster: 1) Convection rather than radiation. As the hot gasses | travel through they stove they are in contact with the mass and | can transfer heat more directly to it, which then spreads | through the mass via conduction. This is aided by... 2) | Newton's Law of Heating and Cooling, which basically says "the | greater the temperature difference, the faster the heat | transfer". Since the gasses from the combustion are around 1000 | degrees or higher (at least initially) they transfer heat much | faster to the mass (several hundred degrees delta) than the | mass transfers it to the room temperature air (one or two | hundred degrees delta). | | Similarly, much of the radiation of the hot inner mass is | absorbed by other parts of the hot inner mass; only the parts | near the outside actually radiate heat away from the mass. ___________________________________________________________________ (page generated 2023-02-25 23:00 UTC)