EcoRenovator - View Single Post - Modifying a wood furnace to increase efficiency

benpope · 03-05-12, 10:18 AM

I found a PDF that has a wealth of information on stove design:
Designing Improved Wood Burning Heating Stoves

There are two that look like good candidates for your retrofit.

First, the 33 gallon in 55 gallon heat exchanger on page 21. An insulated interior barrel lets the flue gasses keep their heat. With the right air flow, this becomes a secondary burn chamber. This is basically a retrofit to turn your regular stove into a rocket stove.

A similar setup, the Library Stove on page 36, uses a heavily insulated burn chamber. You could do something similar with your stove using stove brick on the bottom and a mix of clay and perlite on the walls and top. The insulated burn chamber means higher temperatures for a more complete initial burn. The two 55 gallon drums give a large surface area for radiant heating.

There are some high-mass stoves in there as well. I don't think they would be suited for a shop since they have a huge lag from heat created to heat radiated. However, they are well suited to home heating; they are better at extracting heat since they have a very long chimney with a very large mass around it and produce a low, steady heat like a radiant floor. Permies.com has a lot of discussion on the rocket stove mass heater. They claim that exhaust from a well designed stove should have no visible smoke and be about the same temperature as dryer exhaust. I have played around with small rocket stoves with some success, but I don't have the metalworking skills to make one suitable for the house and I don't have enough space for a big cob stove.

03-05-12, 10:18 AM	#34
benpope Helper EcoRenovator Join Date: Jan 2010 Location: Little Rock, AR Posts: 95 Thanks: 16 Thanked 13 Times in 12 Posts	I found a PDF that has a wealth of information on stove design: Designing Improved Wood Burning Heating Stoves There are two that look like good candidates for your retrofit. First, the 33 gallon in 55 gallon heat exchanger on page 21. An insulated interior barrel lets the flue gasses keep their heat. With the right air flow, this becomes a secondary burn chamber. This is basically a retrofit to turn your regular stove into a rocket stove. A similar setup, the Library Stove on page 36, uses a heavily insulated burn chamber. You could do something similar with your stove using stove brick on the bottom and a mix of clay and perlite on the walls and top. The insulated burn chamber means higher temperatures for a more complete initial burn. The two 55 gallon drums give a large surface area for radiant heating. There are some high-mass stoves in there as well. I don't think they would be suited for a shop since they have a huge lag from heat created to heat radiated. However, they are well suited to home heating; they are better at extracting heat since they have a very long chimney with a very large mass around it and produce a low, steady heat like a radiant floor. Permies.com has a lot of discussion on the rocket stove mass heater. They claim that exhaust from a well designed stove should have no visible smoke and be about the same temperature as dryer exhaust. I have played around with small rocket stoves with some success, but I don't have the metalworking skills to make one suitable for the house and I don't have enough space for a big cob stove. Last edited by benpope; 03-05-12 at 10:27 AM..