BrotherBart said:
All I can tell ya is in my 3.5 cf firebox stove I can load it full and take it up to 550-600 and get overnight burns. Or I can load it around 2/3 full and take it up to 500 and get overnight burns.
Not having calorimetry equipment in my family room I can't give you any heating efficiency numbers.
Well, you'll just have to burn it one way next year and the other way the year after. Report back to us in two years and tell us how much wood you burned each way.
Personally, I don't believe a tightly packed stove is as efficient in combustion as a more loosely packed stove.
My reasoning?
If the air could be forced through all those tight spaces at a high enough velocity, you would get a very complete mixing of intake air and wood gases and efficiency would be so high you wouldn't need secondary combustion, but that's not what's really happening inside the stove. All those spaces are causing individual resistances to mass flow, so air velocities would drop well below flame propagation velocities and some of the wood gases would escape the primary burn zone. These gases must be addressed by the addition of air (and high ignition temps) later on along the way. That's what gives you the secondary burn.
By keeping the stove partially filled, you get a much better mix of air/gas in the primary burn zone. The gases are mixed in the spaces around and above the wood. The turbulence created causes a very even mixture of air and gases, and the burn becomes more efficient. Secondary air is not needed nearly as much because most of the gases are burned in the main fire. To me, secondary combustion is just a way to deal with sloppy primary combustion.
I think you will get a longer burn in the tightly packed small stove with the same amount of wood, but that is more obvious why it is so.
