BTU energy output calculations?

[Model94]

Understanding of course that it depends on burning specifics (wood load, dampening etc etc) curious how to estimate energy output of tent stoves .

[Heavy Duty]

in simplest terms, the larger the stove the greater the energy output only because you can put more wood in it. Thermal mass only evens out the highs and lows of the energy output. Dampening and other ways of exchanging the heat (stack robber) its a difficult one considering every variable.

by all means I'm not a stove expert but this is what immediately comes to mind.

[Undersky]

Hey '94, Mind me asking what your end goal is? Maybe knowing what you are hoping to understand will guide the approach to calculating/estimating energy output.

One really broad way of calculating heat production could be to know the BTUs available from your species of wood and know the volume of that wood burned per time. But really, this calculation won't represent the actual practical heat you stove gives you because there are so many unknown values that each use up some of that theoretical heat before any of that heat gets to warm you, like the amounts of heat used to warm the combustion air, heat your supper pots, or heat that warms the pipe outside the tent or the heat the flows out the top of the pipe!

I sure agree with you and HD regarding the difficulties of accurately including all of the variables when we try to calculate/estimate energy output of our wood stoves. So, I wonder if we could abandon the difficult "inputs equation" like the theoretical BTU in a species of wood, and just measure outputs, instead? We might not end up with a measure in thermal units, but we still might be able to compare useful and practical heat outputs of different stoves, wood types, stove settings, etc.

Also, we may be after the practical / useful output of a stove rather than the actual output; ie: I'd be more interested in the amount of heat that radiates from the stove and pipe to the interior of the tent, and I'm not that interested in the heat that escapes from the pipe outside the tent wall as that "lost" heat is not doing me much good (except all the healthy exercise provided in the processing the % of wood that essentially escaped up the pipe!

Perhaps a measure of "practical output" or "useful output" could be found by measuring the average temperature of the radiant area of the surface of the stove and pipe (that part inside the tent) over time? (I guess we'd have to remove the heat-sucking pot of melting snow from the stove top first!)

Or, to go one step further out, measure the area of the tent wall & roof and compare the average interior temperature to the outdoor temperature over time. If we included the wind chill (some countries measure this in watts/m2), then we could calculate the rate of heat loss from the tent to the outdoor environment. I think this "lost heat" through the tent wall would represent the practical heat output of our stove.

Part of my thinking prefers one of these two ways (rather than a typical BTU measurement from inputs) just because they might represent the useful heat our stove is providing.

Just some more ideas! I definitely add my name below HD's name on the list of armchair "non-experts" when it comes to thermodynamics! But, I still find it fascinating in a nerdy kind of way! Ha!

PS: Just for interest, if you would rather consider the "input style" of calculation: https://www.wood-heating-solutions.c...es-btu-values/

[Model94]

Home wood stove manufacturers provide BTU ranges. Id like to estimate energy output needs at various temperatures to consider using LP heaters (which do provide this) in shoulder months. I have one data point - a small 4 Dog Ti stove in a 10x15' snow trekker at 16F can do it but it needs to be kept cranking, so a marginal situation. There is probably a simple correlation with stove volume.