blrman07 wrote:franco b wrote: A stove with better air handling and fire pot design will produce more net BTU regardless of grate to heat exchange ratio than one lacking those features.
This thread started when someone asked a question about extending the barrel on their stove to get more heat radiating surface. Regardless of the fire pot design, type of grate, manufacturer, or fuel type, once you get outside the 27-1 ratio your effective radiation of heat will suffer.
When that ratio was discovered it was during the golden age of stoves starting in the late 1800's to early 1900's. Those designs that were closest to the 27-1 ratio survived. Those that didn't ended up as scrap and melted down.
This is a very simple concept. Did you read the engineering reports cited in this thread?
The ratio of 27 to 1 is a rough guide, a rule but not a golden one since there are other factors than can have a broad influence on it. Paul, in this post explored that.
The Definitive Cylinder Stove Barrel Height Info Thread.
I have no problem with the 27 to 1 ratio but do have a problem with its being emphasized to the exclusion of other equally important things such as the fire where it all begins. To give that force I made a statement (which you quoted) in the form of a rule which I believe to be a golden one. One as true as the sun rising every day. That raised hackles so the fault is mine for not making things clear enough about something you understand as well as I and maybe better.
So to re-state the rule; in a stove whose fire pot and air handling parts provide for more even air distribution and retention of heat within the pot, less combustion air will be needed and less CO gas will be generated and more initial gasses will be burnt. Because less air is needed there is less excess air carrying heat up the flue. Volume and velocity being lower any heat exchange is more effective than in a stove not having these efficient burning attributes.
Heat exchange is also not just a question of area. How closely the flue gas passes the area has a major effect. In efficient exchange the gas is broken up to pass closely to the exchange area. A stove with more efficiently designed heat exchange might very well have a lower stack temp. than one with a larger area. Measuring the center temp. of a smoke pipe as opposed to the side illustrates this very well.
Lastly I did read one report and even provided a link to it. I don't think rebuke was deserved and I think I have shown that things are not as simple as they seem at first glance.