Approche déterministe du séchage des avivés de résineux de fortes épaisseurs pour proposer des conduites industrielles adaptées

Les secheurs connaissent des difficultes pour secher les avives d'epicea de fortes epaisseurs avec les sechoirs industriels classiques. Notre etude a pour ambition d'ameliorer les connaissances sur le sechage des avives de resineux de fortes epaisseurs par une approche deterministe. Le code numerique TransPore, developpe par Patrick Perre, de part sa capacite a simuler les transferts couples de chaleur et de masse dans une planche de bois, est place au cœur de notre approche. Notre demarche scientifique a necessite la mise en place de deux outils : - un dispositif experimental a ete mis en place pour obtenir des informations descriptives sur les transferts de masse s'effectuant dans la planche au cours de son sechage, et sur les contraintes mecaniques engendrees par le sechage. Ce dispositif mesure en continu l'epaisseur des avives, les fentes de surface, et le champ de teneur en eau dans la planche par attenuation de rayons X ; - une unite de calcul des contraintes de sechage a ete developpee et greffee a TransPore (version 1D) pour aborder l'aspect qualitatif du sechage. La formulation mecanique adoptee est monodimensionnelle, et elle prend en compte la courbure eventuelle de la planche pour, par exemple, simuler un sechage dissymetrique. Les resultats experimentaux ont ensuite ete confrontes aux resultats theoriques pour confirmer et valider les resultats predits par la simulation numerique. La comparaison s'est averee souvent tres probante, tant au niveau des transferts couples de chaleur et de masse qu'au niveau de l'evaluation des contraintes de sechage. Ce travail se termine par l'utilisation du code TransPore comme outil d'aide a la comprehension des mecanismes couples qui rendent le sechage des fortes epaisseurs particulierement difficile. Cet outil a montre egalement sa capacite a guider ses utilisateurs dans le developpement de nouvelles conduites de sechage. Cette derniere application ouvre une voie prometteuse vers l'optimisation des tables de sechage.

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