Lumber drying

Abstract

Abstract In this invention means are provided for maintaining an accelerated liquid diffusion rate through the cell walls of green lumber, for the formation of small ice crystals at the surfaces, for the direct transformation of the ice crystals into water vapor (sublimation) as rapidly as they are formed, and for the removal of the water vapor, without damage to the wood. The rate of drying is thus extremely high, being in the order of some 30 to 40 times faster than by forced-air drying and without the losses from cracking, checking and warping associated with the forced-air system. The apparatus includes a sealed chamber in which green lumber to be dried is placed. A refrigeration system consisting of the usual compressor, condenser and evaporator elements is contained within the chamber. The condenser coils are mounted on the sidewalls to radiate heat into the central and upper portions of the chamber. The evaporator is located in the bottom of the chamber to reduce the temperature thereof to a value well below that at which water freezes, and to create a region of very low vapor pressure. A vacuum pump is connected to the chamber for reducing the pressure and temperature therein to a value at which moisture in the lumber is diffused through the cell walls and ice crystals form on the surfaces. Heat from the condenser and the heater ''''sticks'''' disposed between layers of lumber sublime the ice crystals as fast as they are formed, the water vapor therefrom gravitating to the lower region of the chamber where it is condensed and formed into ice. This process is performed in such a way that the lumber never freezes and the subliming action is continuous during the drying cycle.

Inventors

• 👤 Philo T Farnsworth

Bibliographic Details