Renewable Energy Questions/Discussion > Solar (heating or electric)

Passive solar air heater - for home

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eidolon:
Older than that. Pioneer chimneys were massive so they could heat up all day and radiate through the night as the fire waned without maintenance through the night.

DJ:

--- Quote from: eidolon on May 27, 2017, 08:22:59 am ---Older than that. Pioneer chimneys were massive so they could heat up all day and radiate through the night as the fire waned without maintenance through the night.

--- End quote ---

The russian Fireplaces being a prime example.
A ton or more of thermal mass designed to extract a lot of heat from the fire and store it.  A long criss crossing path for the exhaust gasses to traverse and give up a lot of the heat normally discharged and wasted to atmosphere.

I don't know if the emissions were room temp but they were certainly a lot cooler than in conventional designs and massively more efficient that's for sure. .

DJ:

--- Quote from: MadScientist267 on May 27, 2017, 04:17:54 am --- but if you are talking about bringing superheated steam in exhaust gases thru a long pipe where it reaches room temp before it leaves the pipe,

--- End quote ---

No, not thinking of cooling it that much and I suspect it would be actually quite difficult to do that through a conventional flue due to the boundary layer of the gasses and other thermodynamics. I also think that would take an impractically long amount of ducting.
That said, there would certainly be a LOT of heat that could be extracted before the gasses cooled enough to generate the condensation problems.

As mentioned, commercial heaters MUST have a flue temp of 40o or below to gain the max efficiency ratings so it must be possible to get this sort of efficiency without major problems.
When I get a chance, I'll try and look this up to see what I can find. always intersting to find the facts on this sort of thing because rarely is it what you would think.

MadScientist267:
Thing is, you're talking about taking it down to 40C... and condensation happens *during* cooling.

All comes down to the amount of water produced... which for wood, again, I can't say exactly what the dynamics are, but with propane, it's non trivial. However they're dealing with it, the only thing certain in my mind is that they *are* dealing with it hehe

lighthunter:
The heat exchanging isnt as difficult as building a combustion process (at least for wood) that burns very hot and clean. Clean burn is important otherwise heat xchanger will plug.  If i remember correct a company called "garn" uses a refractory ceramic tube to finish the hydrocarbon/oxygen reaction before water immersed flue in their owb. Probably the simpest design ive seen. I dont have so i cant verify. Many others use downdraft to get the combustion temps to 2500F, some of those can b a headache.

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