how do I estimate the efficiency improvement due to burning dry wood?

[begreen]

I hear the cartalk guys commenting - 'Has to be a couple engineers asking this.' This IS their summer enjoyment.

 

[Swedishchef]

[QUOTE=" One way to measure the actual amount of energy required to dry wood from 30%MC to 20%MC would be to place a given amount of 30%MC wood- 10# would be convenient- in an oven and measure the amount of energy consumed while cooking out the extra 1# of water. Our wood-burning experiences indicate that this number will be much higher than the 1120 BTU's indicated in the original example.[/QUOTE]

Yup...that is called bomb calorimetry.

Here's a link to an article where calorimetry was used to calculate "The Effect of Moisture on Heating Value"

http://cta.ornl.gov/bedb/appendix_a/The_Effect_of_Moisture_on_Heating_Values.pdf

And here is another great scientific journal article that explains the composition of wood and it's effect on moisture content equilibrium
(broken link removed to http://download.springer.com/static/pdf/703/art%253A10.1007%252Fs00226-009-0298-6.pdf?originUrl=http%3A%2F%2Flink.springer.com%2Farticle%2F10.1007%2Fs00226-009-0298-6&token2=exp=1469921484~acl=%2Fstatic%2Fpdf%2F703%2Fart%25253A10.1007%25252Fs00226-009-0298-6.pdf%3ForiginUrl%3Dhttp%253A%252F%252Flink.springer.com%252Farticle%252F10.1007%252Fs00226-009-0298-6*~hmac=d15cbc4717e4fc28b5ac389c031f4411b909b923a76e7a353e8479ece9735cc2)

This article explains something that nobody has mentioned and we should take into consideration: one of the byproducts of the combustion of any hydrocarbon IS water. And in order to help evaporate this water, it takes energy: http://mb-soft.com/juca/print/311.html

 

[twd000]

Agreed. That's why it is referred as moisture content. Technical details were provided here ^.

The paper was interesting, but I don't think bomb calorimetry is a valid model for woodstove heating. The calorimeter is by definition a completely sealed system; no smoke or unburned combustion products can escape. By contrast, in a woodstove with inadequate secondary burn, a large portion of the potential heating value is being lost up the chimney as unburned combustion products.

 

[yooper08]

Here's one I found. I skipped towards the end, see page 51.
http://nepis.epa.gov/Exe/ZyPDF.cgi/20008YOS.PDF?Dockey=20008YOS.PDF

 

[Swedishchef]

The paper was interesting, but I don't think bomb calorimetry is a valid model for woodstove heating. The calorimeter is by definition a completely sealed system; no smoke or unburned combustion products can escape. By contrast, in a woodstove with inadequate secondary burn, a large portion of the potential heating value is being lost up the chimney as unburned combustion products.

DOn't forget though: not everything can burn

 

[cptoneleg]

I trust me, I WANT it to help by more than 2%. Otherwise the 10 cords in my side yard are quite a waste of space [emoji23]
I don't believe in voodoo either, I'm an engineer and a BTU is a BTU, regardless of how the fire "behaves". So what am I missing in my analysis?

Dirty ugly glass, and hard to start fires, a clean chimney, and 50 years of wood heating knowledge that dry wood keeps my family warm and sfe from chimney fires.

 

[CheapBassTurd]

Going on the roof to take a look down the pipe for the first time tomorrow.
We started in Feb and ran almost continuous till the end of April, plus night burns
for another 4-5 weeks. Wasn't worried about buildup on a new system, but there were
quite a few "wets" that went in during an established burn, or atop the drys. They
were bubbling/ hissing at the ends before ignition. There was energy being used to
burn off water before energy could be extracted from the splits. We weren't ready nor
as informed last season. Mom grew up on wood and cautioned about "going green",
and to only use it if necessary. I know it's not nearly as efficient but we did what we
had to do, and were careful about it. The box took seemingly forever to take off the
chill. If there's even 1/4" of creo, I'm running the brush down it.

Ready with a WHOLE white oak standing dead now split for the upcoming season.
The stack is now at 70ft long at 5ft high. Rotator surgery in a week so I'm bezerking on
roadside scrounge too to pad the mega-cord further down the property line. In fact it's
a whole house frenzy of mini repairs that take two hands. (Live-in remodel project.)
Coupla soft soffit boards with loose gutter, clean the chimney maybe, spreading gravel, etc.

Chimney report on the potbelly smoke dragon to follow very soon.

CheapMark

 

[bholler]

If there's even 1/4" of creo, I'm running the brush down it.

1/4" of creosote is quite a bit. The recommendation is to clean at 1/8" of buildup anywhere in the system.

 

[CheapBassTurd]

Thank you for the heads up!

'Twas quite sooty but no buildup other than a few shiny spots towards the top.
Not measurably thick anywhere I could see. I'll probably run it thru anyway
even with good drys for the season ahead.

Next Q: Wire or ball ends on the brush? The Country Store has both plus all the extensions.
I had planned to use those ball shaped rocky ends for some real scrubbing.

 

[twd000]

Here's one I found. I skipped towards the end, see page 51.
http://nepis.epa.gov/Exe/ZyPDF.cgi/20008YOS.PDF?Dockey=20008YOS.PDF

Interested paper there. The graph on Page 49 seems to agree with my <10% calculation, but it seems they were considering the "smoke dragon"-era of stove technology. There were several disparaging comments about catalysts, and secondary combustion being "unrealistic" to achieve