CFD modeling of steam thermodynamics, heat transfer and bacteria deactivation in an innovative superheated steam dishwasher using OpenFOAM

Superheated steam is used as a cleaning and sterilization agent in various sectors including hotels and the food industry. In this talk, we consider an idealized three-dimensional dishwasher using superheated steam at 180 °C and 10 bar pressure as a cleaning agent, and discuss the effects of heat transfer, fluid flow, and phase change in the cleaning process. Computational fluid dynamics simulations were performed using the interThermalPhaseChangeFoam solver, a volume-of-fluid solver based on OpenFOAM that accounts for condensation phenomena. First-order Arrhenius kinetics was used to describe the inactivation of the heat-resistant bacterium Geobacillus stearothermophilus. The high-velocity turbulent steam jet reaching the plate increases its surface temperature and thereby kills the bacteria in a short time. A parameter study was also conducted with multiple nozzles and plates to reduce potential areas of low heat transfer and thus low bacterial inactivation. This work provides the basis for further solver development considering the three components of air, steam and water separately, and dishwasher optimization.

L. Abu-Farah and N. Germann. Simulations of thermal phase changes and bacterial inactivation in a superheated steam dishwasher, Physics of Fluids, in press.