Computational modelling and study of flow properties in resorcinol formaldehyde aerogels

Abstract

Aerogels are highly nanostructured open-porous materials derived from various organic and inorganic sources and have a very low density and thermal conductivity [20] Resorcinol-formaldehyde (RF) aerogels are a class of organic aerogels prepared by combining resorcinol and formaldehyde in different proportions in an aqueous solution [27]. These types of aerogels are characterised by high porosity and surface areas and therefore can be widely used in applications such as thermal insulation, energy storage and filtration. The nanostructured material has pores sizes varying from 2-50nm which makes a detailed experimental study of their flow properties challenging. This has motivated a computational study of the flow properties in such organic aerogels. This thesis focuses on the modelling and flow analysis of RF aerogels. A mathematical model of the porous media is first developed using Gaussian random fields and an optimum model is then obtained by sensitivity analysis of the model parameters. A pore network of this model consisting of pores and the connecting throats is then generated using Image segmentation in PoreSpy [15] and permeabilities for various phases determined using OpenPNM [13] and DuMuX [21]. The generated network is validated for the specific surface area and mesopore volume with the experimental data of RF aerogels. To this end, the flow is analysed in detail. Parameters such as average flow velocity and volume flow rate are determined to characterise the permeability of the porous structure. Absolute permeability and pore size distributions of the pore networks are validated by comparing them with the experimental results.