A MODEL FOR THE EFFUSION OF WATER IN CARBON PHENOLIC COMPOSITES

A model is developed for the effusion of water in phenolic composites as the material is heated to moderate temperatures. The model is devel oped from the theory of the flow of gases through a porous media coupl ed with the thermodynamics of the evaporation of water from a condense d, binary mixture. The resulting model accounts for the evaporation of water fr om solid sites in the material to an internal pore network a nd the subsequent flow of water vapor through the pore network. The ma thematical theory is applied by simulating the effusion behavior of wa ter in a thermogravimetric test. The results obtained from the model c ompared favorably with the thermogravimetric measurements. The results also showed a close correlation between the permeability of the mater ial and the rate of evaporation of water from the solid sites. (C) 199 7 Elsevier Science Ltd.