woodburning safety (avoiding the fireplace)

[Christophe]

A small summary table:
http://www.arbao.fr/Docs/ARBAOEquilibreHygroscopiquedubois.pdf

mirror: https://www.econologie.info/share/partag ... ukzJQQ.pdf

Excellent this doc, I put it in image for those who have not yet acrobat or who are too lazy to click on the link:



So very interesting doc I did not know, you see Ahmed he shows that we can easily be under 15% humidity, even at 10 ° C. On the other hand the "after a certain time" is rather vague ... shame because by adding the drying times according to% RH and T °, ​​then the doc would have just been perfect!

Practical example: our wood is stored in our garage at 55% -60% humidity (low because bare ytong walls which "draw" the humidity outwards) and therefore after a "certain time" (or a " certain weather "?) at an average of 15 ° C we can very well have firewood around 10% humidity.

ps: I just made it a subject to more easily find it https://www.econologie.com/forums/sechage-du ... 10065.html

[Did67]

This is why we have much lower rates in materials.
Besides, it is quite impossible to exceed a certain humidity threshold in the materials since at 100% we have more than water !!

Very just.

And at 100% RH in the air, we begin to have fog: the air can no longer contain more water vapor, it condenses into droplets.

Any air that is not at 100% RH will tend to pick up some by evaporation. And all the more so when the air is dry (air at 50% RH will "pump" harder than air at 90% RH). So the water contained in the wood will evaporate to humidify the air ... On the line, the laundry dries, except in foggy weather ...

But on the other hand, in the wood, the water is more and more strongly retained, as it dries.

Hence the fact that an equilibrium is formed between the humidity of the air (RH) and the humidity in the wood, or another hygroscopic product. The same goes for flour - people are always surprised to learn that flour contains about ten% water; for them, it is the very image of a "dry" product!

[Christophe]

Hence the fact that an equilibrium is formed between the humidity of the air (RH) and the humidity in the wood, or another hygroscopic product. The same goes for flour - people are always surprised to learn that flour contains about ten% water; for them, it is the very image of a "dry" product!

Good example.

About dry products, here is a funny little trick.

They say thatit is impossible to swallow more than 3 "petit lu" type dry biscuits in less than a minute... The production of saliva does not follow ...

I have never tried personally but I think it is possible.

To your webcam!

[dedeleco]

In addition to the saliva that does not arrive, by eating ultra dry cakes like the old LU, I catch a beautiful hiccup which only stops if I drink the missing water !!!

By heating the wood well divided or finely split, near a stove or in hot air at 60 ° C, you get very dry wood at 5 to 6% humidity!
With the curves reported by aerialcator, one has to take into account that at 60 ° C, the relative humidity plummets to less than 30%, even starting from 75% to 20 ° C !!
Good stoves should have this efficient pre-drying, because the combustion would be much better and the yield too !!!
The evaporated water will condense in the house on cold spots and heat the house by its heat of condensation, giving a very good overall return !! from 80% to 90 to 95%, even on wood not very dry !!

This physically obvious remark seems very forgotten !!!
Except some boilers of very high-end, very expensive !!

[aerialcastor]

Yes except that to evaporate from the log, the water has gained energy so the balance is zero.

[dodo]

What are and how to reduce (cancel?) The risk of chimney fire?

We can quickly summarize:

a) always burn a quality fuel, that is to say dry and untreated. Do not trust wood deliverers. Re-dry it yourself ... We were fooled once. You can check with a moisture meter to measure the humidity of your wood. The humidity should be between 10 and 15%.

the moisture meter I did not know but it must be practical to check its wood.

[dedeleco]

No chimney fire without soot in the chimney, whatever the burned wood !!!
So sweep as often as necessary (yourself like me) to never have more soot than a few mm and not even a centimeter !!!

coniferous wet burnt: sweep once a week !!
coniferous dry 2 to 3 weeks between sweeps.
Another moist wood like resinous!
Good dry wood 2 to 3 months between sweeps seems safe, but little more !!

We also measure the soot on the deflectors and the stove pipe which are so black that the identical chimney must be swept !!

but if we respect this principle of sweeping so that we never have too much soot, we can burn free conifers (rather dry).

[dedeleco]

aerialcastor realizes:

Yes except that to evaporate from the log, the water has gained energy so the balance is zero.

but this zero heat balance for drying (therefore ideal, since no energy wasted in this drying), comes down to the actual final balance of burning a perfectly dry log at 60 ° C, with 5 to 6% humidity, 2 times less than a 2 year old log dry at 15 to 20 ° C !!
In addition the pollution will be much lower with a very dry log, to add to the balance sheet !!
So the real balance is much better than we think, compared to burning the usual log at 11 to 12% of humidity left at 15 to 20 ° C and 60 to 90% of humidity.
The balance sheet is dramatically better than the not very dry log burnt in the stove as usual because then we heat in the flames to 500 to 600 ° C and more the escaping water vapor, which bothers and cools the combustion a lot. full of soot and pollution, physical reason to burn dry wood !!

[aerialcastor]

Totally agree for the best combustion.

In fact my remark applied:

The evaporated water will condense in the house on cold spots and heat the house by its condensation heat, giving a very good overall yield !! from 80% to 90 to 95%, even on not very dry wood !!

[Christophe]

Yes except that to evaporate from the log, the water has gained energy so the balance is zero.

Not at all agree!

When you dry in the open air you must not provide the latent heat of vaporization which is enormous in the case of water and which will be pumped into the fireplace. It takes more than 500 times more energy to pass 1 g of water from 100 to 101 ° C than from 99 to 100 ° C!

Air drying is not evaporation at 100 ° C very energy-consuming.

So redo drying your wood next to the stove is all good even if it increases the ambient humidity a little which is not a bad thing since heating with wood is known to strongly dry the air.

And I +1 the remark on the improvement of the combustion of course.

The evaporated water will condense in the house on cold spots and heat the house by its condensation heat, giving a very good overall yield !! from 80% to 90 to 95%, even on not very dry wood !!

Strange remark ... if there is condensation (we are talking about the same thing: droplets and apparent humidity on the wall?) Is that the walls are cold, lower than the dew point and therefore that you have thermal bridges and that the condensation energy passes mainly ... in the thermal bridge, i.e. outside ...

And what about the health risk of mold ... and the discomfort provided by a damp wall, and the increase in humidity of its thermal conductivity, therefore of the thermal bridge ... ???

If you notice the phenomenon at home, do something to prevent it, interior insulation is better than damp walls ...