Drying behavior and permeability of Eucalyptus Grandis Lumber

In memoriam of Dr. H. Peter STEINHAGEN Although the increasing economic importance of Eucalyptus lumber to furniture and other value added products manufacturing, its industrial use is still small. One of the main reasons is the difficulty to dry the lumber and related loses of row material. There is a general recommendation in literature to use a low drying rate in initial stages of the process, and changing to a more aggressive drying after removal of liquid water from the lumber. According classical theory about drying of porous material, this point should coincide with the predominance of diffusion phenomena in the moisture movement; which could be determined through the characteristic drying curve of the material. With the objective to get better knowledge about the drying of Eucalyptus grandis lumber, its characteristic drying curve was determined, and the results proved that Eucalyptus grandis lumber is not permeable to liquid flow. Based on its characteristic drying curve, it is possible to suggest the change of drying conditions when lumber moisture content, dry basis, is between 35% and 40%, then starting a more aggressive drying

Drying behavior and permeability of Eucalyptus Grandis Lumber

In memoriam of Dr. H. Peter STEINHAGEN Although the increasing economic importance of Eucalyptus lumber to furniture and other value added products manufacturing, its industrial use is still small. One of the main reasons is the difficulty to dry the lumber and related loses of row material. There is a general recommendation in literature to use a low drying rate in initial stages of the process, and changing to a more aggressive drying after removal of liquid water from the lumber. According classical theory about drying of porous material, this point should coincide with the predominance of diffusion phenomena in the moisture movement; which could be determined through the characteristic drying curve of the material. With the objective to get better knowledge about the drying of Eucalyptus grandis lumber, its characteristic drying curve was determined, and the results proved that Eucalyptus grandis lumber is not permeable to liquid flow. Based on its characteristic drying curve, it is possible to suggest the change of drying conditions when lumber moisture content, dry basis, is between 35% and 40%, then starting a more aggressive drying

Estimativas da umidade de equilíbrio para cidades da Região sul do Brasil.

Tendo em vista que a variação sazonal da umidade de equilíbrio é um fator de suma importância na secagem natural da madeira serrada, o presente trabalho apresenta estimativas do equilíbrio higroscópico para diversas cidades da região sul. As estimativas foram feitas aplicando-se as equações propostas por Simpson, que se baseiam na teoria de sorção de Hailwood e Horrobin, às normais climatológicas fornecidas pelo Instituto Nacional de Meteorologia. Observou-se, para as cidades sob estudo, que a variação anual da umidade de equilíbrio é pequena (inferior a 3,5%), fato que favorecerá a utilização da madeira por acarretar menor movimentação dimensional. Contudo, observou-se também que os valores médios são superiores a 14,4%, condição que prejudicará a secagem natural da madeira nessas localidades.Due to the importance of seasonal variation in the equilibrium moisture content on the air drying of saw wood, this paper shows the estimation for hygroscopic equilibrium in Brazilian southern cities. The values of equilibrium moisture content were calculated according to the method of Simpson based on the sorption theory of Hailwood and Horrobin. In those cities, the annual variation of equilibrium moisture content is small (less than 3,5%), but the mean values are higher than 14,4%. In this condition, the air drying of wood will be slow and unfavorable