Numerical modeling of the medium-density fiberboard hot pressing process, Part 1: Coupled heat and mass transfer model

A mathematical model describing heat and moisture transfer during hot pressing of mediumdensity fiberboard mats is presented. The model is based on conservation of energy, air mass, and water vapor mass, resulting in a three-dimensional unsteady-state problem in which mat properties and state variables vary in time and space. The conservation equations are expressed as functions of the three state variables: temperature, air pressure, and vapor pressure. The model includes conductive and convective heat transfer, phase change of water, and convective and diffusive mass transfer. Resin curing kinetics and latent heat associated with phase change of water are also taken into account. The closing of the batch press and development of the density profile are taken into account by imposing a predefined time- and space-dependent density profile. Calculations are carried out on reference geometry, and mathematical details relevant to the transfer from actual to reference geometry are presented. The system is discretized in space by the finite element method and in time by the Euler implicit scheme. The results exhibit good agreement with experimental measurements and provide information on variables of interest such as total gas pressure, temperature, moisture content, RH, and resin cure.