subject: Wood Drying Kilns For Curing Wood [print this page] In wood drying kilns, a chamber is sealed to retain a negative pressure with respect to the ambient and for storing stacked lumber to be cured and having a concrete floor with embedded heating pipes for circulating heated water to heat the concrete floor to a temperature preventing condensation thereon, and with means for circulating heated air within the chamber and through the stacked lumber to remove moisture therefrom and with the chamber being constantly vented to remove moist air and maintain the negative pressure within the chamber. A tarp is suspended from the ceiling of the chamber above the stacked lumber to enable the tarp to be lowered to cover and seal the top of the stacked lumber so that the heated air flows across the top of the tarp and down into and through an end of the stacked lumber.
In conventional wood drying kilns fans are used to force air through the stacked lumber within a sealed chamber, and baffles are required to ensure that the air is forced through the stacked lumber. In many conventional wood drying kilns such baffling is so insufficient that a considerable amount of the air is forced above the stacked lumber and not through it as is desired. One solution that has been adopted is to increase the amount of forced air flowing in the kiln, which is inefficient as it wastes electrical power and the heat rise caused by the fan blowers may actually result in a sufficient temperature increase within the kiln that it is difficult to maintain the proper temperature control during the wood curing cycle. Venting air to reduce the temperature may result in too dry air in the kiln and damage the wood. Vaporization normally provides natural cooling, but may be insufficient with certain types and thicknesses of wood such as 2 inch thick oak, for example. With such wood the rate of vaporization is too slow to provide adequate cooling to control the temperature of the air in the kiln.
Another problem associated with conventional wood drying kilns is that the use of track-type doors causes sealing problems as the door never returns to the same position from which it started when it is opened and then closed as the seal has molded itself to the previous position the door was in when it was closed. As most conventional wood curing kilns operate with a positive pressure in the kiln it is necessary to have rather tight sealing around the kiln doors.
