Cleaning of toothpaste from vessel walls by impinging liquid jets and their falling films: Quantitative modelling of soaking effects

The cleaning of thin toothpaste soiling layers from vertical glass surfaces by horizontal impinging water jets and the falling films created by the draining liquid were studied. The effect of soaking time on the rheological properties of the soil material, the force required to remove it, and the cleaning behaviour were determined. The adhesive removal model reported by Wilson et al. (2014, Chem. Eng. Sci., Vol. 109, 183–195) and Bhagat et al. (2017, Food Bioprod. Proc., Vol. 102, 31–54) gave a good description of the cleaning behaviour, including the shape of the cleaning front generated by jets from static and moving nozzles. This model was also applied to removal by the falling liquid film: when soaking kinetics are taken into consideration, it gives a good description of this process as well. This is the first study considering the effect of soil soaking on cleaning by water jets and falling films.