Investigation of mass transfer phenomena affecting emission rate of gaseous compounds from porous solids

The main objective of this study is to investigate the mass transfer phenomena affecting the emission of acetone from a porous solid. In order to simulate this type of emission in a laboratory-scale and in a repeatable way it was decided to set up a system consisting of a dry solid layer with an underlying wet layer. This type of investigation aims to give a scientific basis for the understanding of the factors affecting emission rates when sampling solid area sources with a wind tunnel system. This in turn is important in order to make results obtained with different devices somehow comparable. The study was carried out by following a modellistic and an experimental approach, and then comparing the results. The comparison of experimental and modelled results shows a good agreement, proving that the developed model is able to describe the phenomenon, thereby taking into account the phenomenon intra-solid gas diffusion, as well as capillary rise of the liquid. As a final result, the proposed model is capable to describe properly how the emission rate from a porous solid is affected by the sweeping airflow velocity, which was the final purpose of this study. Although the developed model is valid for the simplified experimental set-up studied (consisting of a dry solid layer with an underlying wet layer and involving the use of pure acetone), the understanding of the phenomena affecting mass transfer in this simplified situation can be transferred to the investigation of diffusion of other compound through more complex solids.