This master thesis presents a new description of the function for determining the sorption rate in multiphase Fickian model of heat and mass transport in wood. Changes in temperature, vapour pressure and bound water content in wood are considered as coupled heat and mass transfer. As such, they are written by a system of four partial differential equations. This basic system of equations is solved using the finite element method with the help of the Matlab PDE Toolbox. The main purpose of the new function for the sorption rate was to improve the convergence of the numerical model and consequently reduce the calculation time. The new function is defined by five independent parameters and a 3rd degree polynomial function. The optimal value of the considered parameters was determined by parametric studies, in which the results of the new model were compared with the results of the already established model. The results showed that, for the most considered humidity states, the convergence of the new model is better or at least equivalent to the convergence of the established model. The downside of the new model was revealed when dealing with high moisture states, when the amount of bound water in the wood began to approach the equilibrium state. In this case the convergence of the new model was worse than the convergence of the established model.
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