• Post Reply Bookmark Topic Watch Topic
  • New Topic
permaculture forums growies critters building homesteading energy monies living kitchen purity ungarbage community wilderness fiber arts art permaculture artisans regional education experiences global resources the cider press projects digital market permies.com all forums
this forum made possible by our volunteer staff, including ...
master stewards:
  • Nicole Alderman
  • raven ranson
  • Jocelyn Campbell
  • Julia Winter
stewards:
  • paul wheaton
  • Burra Maluca
  • Devaka Cooray
garden masters:
  • Anne Miller
  • Pearl Sutton
  • Joylynn Hardesty
  • Shawn Klassen-Koop
gardeners:
  • Joseph Lofthouse
  • Bill Crim
  • Mike Jay

Intake Heat Exchange?  RSS feed

 
Posts: 55
Location: Zone 6b, Ontario, Canada
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Hello fellow forum goers.

I was wondering if anyone of you ever played around with heat exchangers, in the conventional sense instead of teh rocket stove thermal mass sense? All houses, no matter their heating methods need some air intake and exhaust out. Some of the more energy efficient ones use heat exchangers to warm up the incoming air. This problem of sucking in cold air is quite large particularly when using a wood burning stove that requires a large flow of fresh air to function.

Now most commercial heat exchangers are complicated and expensive, but I don't think that they have to be. Has anyone seen, or better yet designed and used themselves, any hand made heat exchangers for the warming up of intake air?

Thanks in advance,
   Jonathon
 
Jon Wisnoski
Posts: 55
Location: Zone 6b, Ontario, Canada
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Posting this returned better results than any of my searches.
Reading these related posts now:
https://www.permies.com/t/18906/Air-Supply-order-magnitude-improvement
https://www.permies.com/t/1450/rocket-mass-heater-air
 
pollinator
Posts: 1936
Location: Toronto, Ontario
144
bee forest garden fungi hugelkultur cooking rabbit trees urban wofati
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
The best commercially available woodstoves already route their air intakes in such a way that the waste heat warms the incoming cold air. The one I have used most recently involved an airway passing under the firebox, overtop of the ash drawer, with I think a quarter turn around the chimney.

Realistically, when building my RMH, I will just route the air intake in a channel around the burn tunnel, and probably past the side of the top of the riser. This presupposes that I will have designed it properly, with enough draw that a longer intake will work.

-CK
 
gardener
Posts: 2609
Location: Upstate NY, zone 5
95
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
You don't want to cool the burn tunnel or riser at all, but routing the intake around the top of the feed tube is wholly beneficial. You want to keep that opening cool to reduce flame creep and smokeback, while preheating the secondary air to the P-channel.
IMG_1346.JPG
[Thumbnail for IMG_1346.JPG]
feed tube insert
IMG_1347.JPG
[Thumbnail for IMG_1347.JPG]
side view
IMG_1351.JPG
[Thumbnail for IMG_1351.JPG]
recess with airflow space around insert, feeds p-channel at left
IMG_1352.JPG
[Thumbnail for IMG_1352.JPG]
insert in place
 
gardener
Posts: 1437
Location: latitude 47 N.W. montana zone 6A
127
cat
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Wow Glen, nice,  how long has that been in use ?  I couldn't see any spauling on it. After the second season my P channel was warping ,by the end of last season it was warped and spauled badly.... sadly I haven't had time to cut a new one, so mine has been in use all winter... 4 burning seasons,  Its definitely shot now. 
 
Chris Kott
pollinator
Posts: 1936
Location: Toronto, Ontario
144
bee forest garden fungi hugelkultur cooking rabbit trees urban wofati
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
You're absolutely right, Glenn, that was clumsy of me. I didn't intend to suggest that the burn tunnel or riser be cooled. That would be less than ideal.

-CK
 
Glenn Herbert
gardener
Posts: 2609
Location: Upstate NY, zone 5
95
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
The photo is from the beginning of the first winter. The tab that serves as the P-channel outlet has warped at the bottom, with a ripple/bulge toward the feed tube an inch wide by 1/2" out. It doesn't seem to have noticeably corroded, though, after two winters. I expect in a few years I may need to cut off the tab and bolt on a thinner replaceable tab.
 
Glenn Herbert
gardener
Posts: 2609
Location: Upstate NY, zone 5
95
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
The insert also serves to completely eliminate wear or damage to the mouth of the feed tube, and makes sliding a piece of cement board as a damper smooth and easy.
 
Posts: 36
3
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Retired 2 stage furnaces are a good source of heat exchangers. Contact an independent HVAC installer and see if they can save you a condensing furnace. I got one that had a stainless steel heat exchanger for the secondary condensing stage. It is very sturdy and I am hoping to use it after the first bell on my heater for heating incoming air. I have not decided yet if it will be for all air or just secondary.

One side affect of heating air is you are getting less oxygen per cubic foot of air because of the expansion from heating. The heat is necessary for secondary air to maintain combustion but not necessarily needed for primary air. Heating the primary air may contribute to increased pyrolysis making more demand for secondary air.

I think the idea has potential.
 
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
Boost this thread!