Logging near public places.

[SwampDonkey]

There might be some wicking on the ends of the logs near the surface, but when it's freezing water is bound to the wood and won't migrate out to the drier areas of the log ends. I've not seen checked winter cut logs. I have seen it on wood that was cut in the fall and not hauled 'til later.

[beenthere]

Freeze drying happens....that was a once-upon-a-time method proposed for slow drying walnut gunstock blanks.. problem was they dried too fast. 

 

[SwampDonkey]

Heat of wetting is where energy is given up when wood takes on moister. I think the Freeze drying process is a bit different than a stick of wood in a pile under the snow at -10 F under normal atmospheric pressure (26-30 in Hg or there abouts) and RH of 40-50 %, which is normal for my area in dry winter days. If your going to liberate water from deep inside a stick in cold temperature I think there is some pressure involved in the process to reduce the energy needed to liberate the water.

Maybe I'm just confused. 

edit: had my units mixed up.

[Gary_C]

Freeze drying occurs as a result of the process of sublimation which is a phase change from liquid directly to a vapor at temperatures below the Triple Point and it is driven in this case by the energy in sunlight. This sublimation occurs all the time during the winter, and you can see the results when the snow starts to get that porous or coarse grained look. And it happens even when the air temperature never gets above freezing.

From Wikipedia  Triple Point of Water:

The single combination of pressure and temperature at which pure water, pure ice, and pure water vapour can coexist in a stable equilibrium occurs at exactly 273.16 K (0.01 °C) and a pressure of 611.73 pascals (ca. 6.1173 millibars, 0.0060373057 atm). At that point, it is possible to change all of the substance to ice, water, or vapor by making arbitrarily small changes in pressure and temperature.

What this all means is the frozen water in the logs will make a phase change directly to water vapor even while sitting on the landing in below freezing weather. I have no idea how much moisture they can lose, but I have seen all species of logs that were cut in the coldest temperatures end up with cracks in the ends of the logs, and that includes ones that have been end sealed.

[SwampDonkey]

Yeah, but your hovering very close to the melting point. Even -0.0001 C is freezing. A slight change in pressure in the right direction and your in business. Now as the days become longer in February and onward, the sun is real warm on an exposed wood pile in the southern aspect, snow even melts even though the shaded air temperature can be 24 F. Dirt on the wood yard even melts the yard each day. The water ain't going to move when she's -10 F out.

And yes the energy comes from the sun, or the wood pile wouldn't season.


When splitting firewood, it's a lot easier when wood is frozen and green. You'll know if it's dry, it ain't so easy.



My understanding of sublimation involves a vacuum chamber to control pressure and cold air flow is used to wick moisture from the wood. It's done at around 30 F and -16 mm Hg. Done for hardwoods. Lower vaccum does not produce faster results and costs more.

For softwoods a dehydration unit at colder temperatures is used at  -2 to -100 F typically and takes more energy for cooling than the ealier method. By adjusting the atmospheric pressure within the dehydration unit moisture can be removed from the cells with minimum structural damage to the cells. The wood is dried in a chamber. The cold, dry air is circulated through the chamber, where it picks up moisture from the wood. The wet air is then removed from the chamber, heated, dried and cooled for recirculation into the chamber. The cool dry air is blown in under positive pressure to wick away the moisture.

Taken from: Patent Storm Website