Thermal phase change and bacterial inactivation in a superheated steam application using CFD simulations

Superheated steam is a promising technique used in applications to kill bacteria and sanitize dishes. To analyze the different phases of the cleaning process, OpenFOAM simulations were performed in an idealized 3D applications geometry with a nozzle and a plate at a temperature of 180 °C and a pressure of 10 bar. The interThermalPhaseChangeFoam solver [1] was used to calculate the heat and mass transfer between phases. The K-omega-SST turbulence model was used to capture the turbulent flow conditions. Bacterial inactivation was modeled using first-order kinetics in combination with the Arrhenius equation. An unstructured tetrahedral mesh of the dishwasher geometry was created using ICEM CFD v.17.1. Due to the high flow velocity of the steam and the strong steam shocks, which resulted in an increase in temperature, a higher steam condensation rate, and a lower bacterial concentration, the bacteria were initially deactivated at locations near the perimeter of the plate. Most bacteria on the plate surface were deactivated in a short time of about 10 s. This work forms the basis for future development and optimization of next generation superheated steam applications.

[1] M. Nabil, A. S. Rattner. SoftwareX, 5:216-226, 2016.