Modelling of the drying process of polyurethane foam

✍ Scribed by A. Sabbahi; J. Bouzon; J.M. Vergnaud

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 315 KB
• Volume: 28
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(92)90194-7

✦ Synopsis

The drying process of a polyurethane (PU) sheet is studied with the help of experiments and a numerical model, by considering not only the evaporation of the liquid water but also the diffusion of the vapour through the foam. Because of this evaporation, the front of the liquid in contact with the vapour is assumed to move through the foam. There is thus a problem with moving boundaries. The rate of evaporation is proportional to the gradient of the vapour concentration at the liquid front and also to the rate of motion of this front. In spite of the fact that a concentration-dependent diffusivity can be accounted for by the model, the diffusivity of the vapour is assumed to be constant throughout the process. The rate of vapour release out of the external surface of the PU sheet is proportional to the difference between the actual concentration of vapour at the PU surface and the concentration required to maintain equilibrium with the surrounding atmosphere, and also to the gradient of concentration of vapour at this surface. The model is able to provide kinetics of drying correlating well with experiments, with a constant rate of drying during a large part of the process.