Current BTU output: dependent on stove temperature, load size of firewood, or both?

[Propane_Poor]

If I have a cat stove burning at a particular temperature, is that what determines the current BTU output at that moment, or does it also depend on how much wood is burning?

 

[1kzwoman]

If I have a cat stove burning at a particular temperature, is that what determines the current BTU output at that moment, or does it also depend on how much wood is burning?

It involves not only ”how much” wood but the type of wood, size of wood, the moisture content of wood, E/W or N/S loading of wood, your skill level engaging the cat, weather, and more. Other member will add more information I am sure. Keep asking questions!

 

[Poindexter]

I prefer to look at longer slices of time than per instant. With a wood stove I would prefer to know how many pounds per hour of wood is getting burned. And I guess the MC of the fuel. From there we can look up the efficiency of the stove and have a pretty good idea how many BTUs per hour are getting released into the home.

 

[bokehman]

BTU output depends on the temperature of the exterior of the stove. And if you increase that temperature a small amount it increases the output a lot. e.g. raising from 750º to 900º will double the output (black body radiation).

But obviously you need sufficient fire inside the stove to maintain the exterior at that temperature.

 

[Woodsplitter67]

BTU output is based on 3 things.. 1 how much wood is in the box. 2 The type of wood.. oak has more btus then poplar.. How much air your letting in the stove.

Its mostly air control.. My stove is a cat stove also. right now I have a half load of oak in it, with the air all the way back and the stove is at 400 degrees with a cat temperature of 875.. If i turned the air all the way up, that same load will run at 700 degrees. If i keep the same load in and turn the air all the way up and open the bypass Ill probably have to replace the warped damper housing because that same load went to 875/900 for to long of a period..

Your air control is pretty much what is determining heat output.. If you had a load of softwoods in it you can still run it on the hotter side with more air, you'll just have to reload more often

 

[stoveliker]

All of the above.

My perspective: yes. The temperature of the stove (i.e. the heat generated inside the stove) determines the output, at that moment. Not the quantity of wood. You can burn a little wood very hot (high number of BTUs coming out) or a lot of wood very low (but be careful of creosote), which is a low number of BTUs coming out.

 

[Gregminct]

BTU output depends on the temperature of the exterior of the stove. And if you increase that temperature a small amount it increases the output a lot. e.g. raising from 750º to 900º will double the output (black body radiation).

But obviously you need sufficient fire inside the stove to maintain the exterior at that temperature.

Bokehman. I modeled black body radiation. Pretty easy, surface area, temperature kelvin to the 4th power. Anyone know if a full model? Convection, conduction, black body? When they do any epa efficiency test, someone must have figured this out? I believe there should be a stovetop temp to BTU output curve. Wood, fuel, pounds, flue temp, all driving BTUs but the stove surface temperatures should be uniquely correlated with BTU output. Any variables that are involved with producing that temperature are not important if we just want to know how many BTUs are coming from those surfaces?