Drying firewood; hygroscopic balance

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Christophe
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Drying firewood; hygroscopic balance




by Christophe » 20/10/10, 10:26

How does the wood dry according to the humidity of the ambient air? Here is an interesting table that answers the question:

Image

.pdf Version: https://www.econologie.com/fichiers/par ... ukzJQQ.pdf
(Thanks AerialCastor :) )

Read also: https://www.econologie.com/sechage-bois ... idite-air/

Practical example: your garage is at 65% humidity and 15 ° C on average, the wood stored inside will stabilize at 12% humidity. Which is very good humidity for firewood (which must be as dry as possible). The profession indeed considers wood ready to be burned at 20% humidity.

Only still unknown: what is the order of magnitude of this "certain" time?

Table drawn from this topic on the security of wood heating and wood quality.

You can check the humidity of your firewood with an electronic moisture meter.
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dedeleco
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by dedeleco » 20/10/10, 14:25

By heating well-divided or finely divided wood, near a stove or in hot air at 60 ° C, very dry wood is obtained at 5 6% moisture !!!
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 (double combustion, gasifier type, burning gas from very hot wood) should have this efficient 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 !!

So drying the wood warm near the stove or above or below can be very effective.
This physically obvious remark seems very forgotten !!!
Except some boilers of very high-end, very expensive !!
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dedeleco
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by dedeleco » 20/10/10, 14:36

The only one still unknown: what is the order of magnitude of this "certain" time?

Can be very fast if the wood is very finely divided, sawdust pellets (minutes) and if the air very dry hot circulates quickly around the wood well ventilated and a few days on pads or ultra-split.
It is the same as for drying thick or thin linen, time for tee-shirt wet in the sun !!
In the sun the logs (10cm) in the sun at 20 ° C and more during the day dry in less than a summer, if they are kept above 20 ° C at night away from night condensation, often enormous, which destroys almost all the drying of the day by wetting the logs !!! (see aerialcastor curves between day and night, ie 30 ° C with sun on day 50% wet and at night 10 at 15 ° C and 100% humidity which condenses liquid water on the log) !!!!
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aerialcastor
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by aerialcastor » 20/10/10, 20:36

The only one still unknown: what is the order of magnitude of this "certain" time?


Answers here:
http://passion.bois.free.fr/le%20materiau%20bois/sechage%20des%20bois/sechage%20du%20bois%20.htm
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by dedeleco » 21/10/10, 00:02

very informative :
Well-conducted drying should allow the wood to dry quickly enough without deforming or altering it.

It is wood for carpentry and furniture and drying on a different scale from that of burning wood, where deformations and alterations are of no importance !!
It can go brutally, instead of controlling with great care the temperature and humidity over time!
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sspid14
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by sspid14 » 06/12/10, 19:03

During a training, I was visited a house where a passionate about solar panels and renewable energies lives.

He has put a few square meters of thermal panels which give him "too much" hot water in summer so he heats up his wood chips. He can thus buy his wet pads and therefore less expensive and dry them as he wishes.
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