Cleaning is a regular and important process in the food, bioprocessing and pharmaceutical sectors, and is essential to remove fouling deposits and avoid contamination or product crossover. Industrial cleaning is often performed in place, by circulating liquids through the processing equipment in order to remove any residual product. These operations incur penalties in terms of lost productivity and energy consumption.
Professor Ian Wilson, from the Department of Chemical Engineering and Biotechnology, has been studying how to optimise these cleaning operations. Fouling and cleaning are rarely uniform, as manufacturing lines feature devices with complex geometry and non-uniform flow patterns, resulting in spatially variable cleaning rates. Professor Wilson uses a combination of laboratory experiments and quantitative modelling to investigate the cleaning of soluble soil layers in these conditions.
In some cases, a cleaning front may develop between the clean and soiled regions in the flow. As the soil is progressively dissolved, this front gradually recedes. Hence, any model of the front dynamics – a Stefan problem – should be coupled with a model of the non-linear rate of transfer of mass from the soil layer to the solvent layer – a Graetz problem.
During the seminar, professor Wilson presented recent experimental and numerical work on this topic. He and his team have been studying the flow which develops in a long, rectangular duct, as well as that in a radial flow cell. These flows are known to generate striations and recirculation zones, leading to regions with noticeable changes in cleaning behaviour.
Professor Wilson’s work on surface cleaning is ongoing, and you can read more about it here.