Optimization of the process water distribution for hot water shower sterilization of bags and bottles: A numerical and experimental study

Hot water shower sterilization is crucial for ensuring patient safety in the pharmaceutical production of liquids in bottle- or bag-shaped containers. The same principle of cascading water showers for heat transfer is also used in the food industry for pasteurization. However, there is limited research on validated simulation models to optimize energy use and process time. This study experimentally validates a numerically efficient two-step multiphase Computational Fluid Dynamics (CFD) simulation model for shower heating and cooling on a lab-scale test bench. Flow and film regime analysis, product temperature measurement, and particle image velocimetry (PIV) are conducted to assess the heating and cooling of glass bottles and polypropylene bags. Varied process water flow rates and distribution tray designs were tested. The slowest heating and cooling zones of the bottle were identified at 2% and 98% of the bottle’s filling height, respectively. The temperature deviations between measurements and simulations were mostly within the margin of measurement uncertainty. The novel application of PIV further validated the internal flow characteristics predicted by the simulation model. An optimized water distribution tray design with a reduced hole pitch, tested experimentally and through simulation, significantly reduced the heating and cooling times of the glass bottle at lower volume flow rates. The results of this study, both experimental and numerical, demonstrate that optimized water trays can shorten sterilization or pasteurization cycles even at reduced volume flow rates while also reducing energy consumption.