Model of convective drying of Resorcinol-Formaldehyde gels to xerogels

Kurzfassung

Drying of a wet gel with an inherent fractal solid nanostructure and pores of mesoscale sizes is a complicated process of evaporation of the pore liquid, a visco-elastic and visco-plastic response the solid network, gas transport at the gel surface and transport through the pores. In this paper an analytical model is derived that takes into account convective–diffusive transport in a drying cabinet and permeation through the pore space. The analytical model neglects any deformation of the solid network. It only calculates the gas transport. The model is compared with experimental results obtained by drying of resorcinol-formaldehyde gels in a drying cabinet having a fan. The agreement between experiments and model is good in light of the simplifications made and thus allows to calculate drying time for various sample geometries and flow characteristics expressed by Reynolds number.