BTU question

[blkcloud]

When reading the btu chart I see that values each wood has.. what im wondering is.. if there are two different types of wood with the same value, does that mean they will both last the same length of time in the heater? or can one put out the same amount of heat as the other but not last as long ?

 

[svk]

Most certainly they can have different burn characteristics. For instance take tamarack. It doesn't have a super high rating but will burn hotter than Hades while it lasts. Much different than a similar rated hardwood that will burn slower and release heat more gradually.

 

[Fubar]

basically all wood has about the same amount of stored energy per pound , the denser woods will have more stored energy , lighter woods have less , but all have different burning rates that effects how they release the stored energy , of course dense woods burn the slowest and light woods burn the fastest , i can tell the difference in all of them , no two are alike , some are very similar like oak and hickory both are slow burning but the hickory burns a little hotter , like cedar and pine both have about the same burn rate but the pine burns hotter due to the resin , the same amount of pine by weight has the same amount of stored BTU's as hickory by weight , the pine will release them quicker and the hickory will release them slower , i don't know if this helps answer your question ?










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[cus_deluxe]

what they said

 

[Marshy]

The BTU chart is not exact. I believe it is measured data from a long time ago, and keep in mind the moisture content will alter the BTU's available to the user. Higher moistre content means less BTU's available to the user because some of them are used to convert the moisture to steam so it can be burnt.

I agree with the comment about BTU/lb, most woods are about the same. Its an interesting observation but not very useful. I say that because we are usually limited by volume we can fit into our burners, not weight. Hence it makes sense to list BTU's per unit volume (cord). And since hard woods weigh more per unit volume they have more BTU's per unit volume and that translates into longer burn times at a fairly constant heat output of your burner (BTU/HR).

However, outdoor wood boiler owners think that burning green wood is best because after 20 hours they still have a large bed of hot coals. What they fail to realize is they waisted a lot of time and BTU's drying out green wood so it can be burnt which means they think the burn times with green wood are great but dont realize they give up a lot of efficiency...

 

[zogger]

Tons of differences, multiple tons of variables. Denser and harder and dryer are the best, everything else drops from there.

This whole deal made me think of something else, there are no heaters on the market, as far as I know, specifically designed to burn larger quantities of softwoods. Pretty much everything is designed for this theoretical perfect burning wood, etc, which for most people doesn't exist.

 

[Streblerm]

In my experience even the same species of tree can have different burn characteristics. A tree grown under some stress with tighter growth rings will burn differently than one grown under better conditions. Even parts of the same tree will burn differently. The base and crotches tend to be denser than other parts of the tree and newer limb wood will be less dense.