Balance of Energy in a Kiln of Drying Wood

Abstract

The equations of energy balance were determined in a kiln of drying wood and the energy consumption was calculated for three values of initial moisture: 62, 72 and 82 % base dry. The dimensions of the drying chamber are: 5,81 X 1,66 X 2,23 m (Length X Height X Width), the wooden volume, white cedar, is of V=10,93 m3. The biggest energy consumption was obtained in the stage 1 where it is required to increase the kiln and lumber temperature from its initial values to the dry-bulb set-point temperature. This energy diminishes in the measure that the initial humidity falls and it should be used to calculate the heating device. The biggest sources of consumption of heat are: (1) the heat required to transform water into vapor and to break the bonds between wood fiber and absorbed water; (2) The heat required to warm up the fresh air fed from outside to the kiln, which is used to replace the moist air that flow inside the chamber to the wet-bulb set-point temperature. Seven suggestions to reduce the energy consumption were discussed.