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vertical chimney 2.5x powerful/effective than heat riser -- innovators event podcast #2 response  RSS feed

 
Posts: 17
Location: Detroit, Michigan
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while listening (enjoying) the 2nd 'innovators event' podcast, i heard all agree to Paul's statement that a vertical chimney is about 2.5 times more effective than the heat riser, in terms of pump-power.
reading through this post (http://www.permies.com/t/27052/rocket-stoves/external-chimney-RMH), i can also refer you to Peter's quote of: "Make the chimney taller. Double hight of the heat riser (and barrel) gives approx. double pumping power."
also from the same post, also from the same Peter: "As long as the temperature inside the heat riser is much higher than in the space between the insulation and the inner surface of the barrel, the pump should work. So the exhaust gases can be cooled down to any temperature without affecting the function of the RMH."

i will be piping my 8" RMH into an existing, 35ft chimney. if the above is true, and an 8" system gives me 50' run of horizontal ducting (incl. 5ft per elbow) through the mass... do i then have at least (a theoretical) 100' of additional run to play with? or is this outrageously simplified?
provided my exhaust is above the condensation-point of 122 degrees f, and the chimney flue is warmer than the outdoor ambient temp, can i add another 'run'? though, what i have in mind is not more horizontal ducting.

what i do have in mind is if i can seal-off the fireplace and make 2nd bell in there? or, preferably, a plunger-tube within the sealed fireplace?
i would like to keep that hot air (above 130f) in-house as long as possible, in contact with mass for as long as possible.

 
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Hello Greg, glad to see you posting another idea. I'm a newbie as well, still ironing out details for my first build also. I just wanted to say I love your story and effort in an off grid "revitalization" in Detroit. Im excited to see how your efforts pan out.

Being new, I'm not the guy to give you advice on your attempt at innovative ground breaking, especially since your comfort ( and survival ) depends on getting this right !


I did want to suggest tho, you post a sketchup pic or even a drawing on a napkin of what you're contemplating. I THINK I'm following your idea, but a picture is worth a thousand words after all.

Side point, I've listened to those discussions on the Podcasts at least a dozen times. That batch box is getting even the veterans excited about new designs and breakthroughs !
 
pollinator
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Greg C. : That is 50' minus 5 feet for every elbow, Because with Bells the hot air stratifies at the top of the bell, an increase in pumping power
does not pump the heat out of the house !

My strong recommendation for you is to build conservatively your 1st rocket system, you may be able to install a bypass damper, that will allow
you to warm up your 50' 8'' system and then switch over to a system using more of the chimneys mass for additional thermal mass storage, but
you will need the simplicity of a basic system as a fail-safe to fall back on. For the good of the Craft ! Big AL

 
See where your hand is? Not there. It's next to this tiny ad:
What makes you excited about rocket ovens?
https://permies.com/t/90100/excited-rocket-ovens
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