PREDICTING MOISTURE-CONTENT FLUCTUATIONS OF WOOD ACCOMPANYING THE WEATHER AND SEASONAL-CHANGES OF ATMOSPHERE

To predict moisture fluctuations of wood accompanying the weather and seasonal changes of the atmosphere, changes in moisture content of woo d of various thickness were simulated by the numerical method based on finite differences. The suitable surface emission coefficient and the hygroscopic isotherms considering the hysteresis effect were reported in the previous paper. Moisture content changes of wooden plates of f our species with different thicknesses also were measured. Moisture co ntent changes predicted for a year were analyzed. The results are summ arized as follows: 1) Because the calculated moisture content fluctuat ions agreed fairly well with measured ones, the moisture content fluct uations for a year could be predicted. 2) From an analysis of the dail y maximum and minimum moisture contents of wooden plates of different thicknesses, the daily width of moisture content fluctuations of wood accompanying the weather and seasonal changes of the atmosphere were a ffected by the thicknesses of the plates. 3) The mean moisture content fluctuation range within a certain period was calculated for plates o f various assumed specific gravities and thicknesses. The mean moistur e content fluctuation range increased with increases of the period of atmospheric change, and the relationship was affected remarkably by th e thickness of the wood. 4) The moisture content fluctuation within a wooden plate also was calculated. The moisture content changes within thick plates were limited only near the surfaces for daily atmospheric changes, and the range of moisture content changes spread to the inne r layers with increasing periods of atmospheric changes. For thin plat es, however, the moisture content changed so throughly and widely with atmospheric conditions within the plates.