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 developed from the theory of the flow of gases through a porous media coupled with the thermodynamics of the evaporation of water from a condensed, binary mixture. The resulting model accounts for the evaporation of water fr om solid sites in the material to an internal pore network and the subsequent flow of water vapor through the pore network. The mathematical theory is applied by simulating the effusion behavior of water in a thermogravimetric test. The results obtained from the model compared favorably with the thermogravimetric measurements. The results also showed a close correlation between the permeability of the material and the rate of evaporation of water from the solid sites. (C) 1997 Elsevier Science Ltd.