Vacuum Kiln

[bowlblanksandmore]

Den,

I have a question? If you pull a 30 torr vacuum on a charge of lumber, but do not add any heat will the wood still dry slowly or would the temperature of the lumber have to to be above the water vapor boiling point of 84 degrees F?

Also is there a reason for starting the drying process at a lower vaccum? Is this so that you do not remove to much of the free water to fast?

Am I reading what Serg is saying right? Since he leaves the humidity in the chamber and removes it as condensate at a set rate per cycle the lumber cannot dry to fast because the surface is allways damp from the humidity in the chamber?

Just trying to wrap my mind around all the information I have been reading and trying to pack into my brain.

Craig

[Den Socling]

Craig,

If you pulled to 30 Torr and didn't add heat, water would evaporate and the vapor would carry heat away from the wood. The wood would be cooled by evaporation until the vapor pressure of the water in the wood would be below 30 Torr. Then, evaporation would stop.

I start new loads at low pressure for a number of reasons. Low pressure means low boiling point which results in low wood temperature. Also, the first hours of drying are not the fastest so the pump doesn't need to move the maximum amount of vapor. Vac pump capacity diminishes as you reach the low end of the pump curve.

Sergey's kiln works like a superheated steam vac but without the fans. To get convection he has to have air and/or vapor in the chamber. To create circulation, he has to condense vapor at the top/center of the chamber.

Den

[Tom_Averwater]

Den,
    Any recent updates on this project? I've been lurking  in the shadows till now. My brother-in law is an Electronics Engineer.  I think he could do the electronics for me.   Tom