Improvement of an annular thin film UV-C reactor by fluid guiding elements

Abstract

In this paper special elements are inserted into an annular thin film UVC reactor to guide the laminar flow. These “Fluid Guiding Elements” (FGE) divide the flow into three separated laminar currents that are alternatingly directed through a small gap of 0.6 mm facing the UV source by turns. Computational fluid dynamic simulations have been used to visualize the flow dynamics inside the reactor.The residence time distribution and the Bodenstein number show an increase of back mixing in the reactor with the elements. An Iodide/iodate actinometry comparison has shown a better dose distribution throughout the treated volume based on the FGE. The inactivation of E. coli DH5α as an exemplary organism could be improved by more than 4 log levels after 5 passes through the reactor using the FGE independent of the flow rate. The absorbance of a model solution was varied by different dye concentrations and the use of FGE improve the inactivation of Saccharomyces cerevisiae. Industrial relevanceThe stabilization of liquid foods before bottling is a crucial aspect. The consumers often do not accept a chemical additive like sulphites in wine or dimethyl carbonate in juices. A physical alternative is the UV-C Treatment. In contrast to a turbulent flow a laminar flow has a far lower pressure drop. Therefore, a lower amount of energy is needed to pump the liquid. This study shows that with fluid guiding elements a sufficient inactivation can be achieved with laminar flow.