(246f) Computational Evaluation of the Performance of Three Treatment Chamber Designs for Electric-Field-Assisted Microbial Inactivation Process

Radio frequency electric field (RFEF) is widely recognised as a food processing technology. A Multiphysics model was developed predicting the electric field, flow, and temperature distribution in various RFEF treatment chambers, with salt solution having electrical conductivity 0.05 Sm^-1. Electric field simulations revealed high intensity peaks at the insulator-liquid interface in co-linear design, and at edges of electrodes in parallel-plate design, forming electrical hot spots, which were less prominent in a novel Steinmetz design due to its geometric characteristics. On the other hand, in few areas inside treatment zone electric field reduces to almost zero with Steinmetz, while parallel-plate demonstrated the most uniform electric field distribution inside the treatment zone. Due to geometric variances, co-linear chamber required high voltages to achieve equivalent volumetric averaged electric fields within treatment zone compared to other chambers, despite of having similar treatment zone volume. Due to high voltages, demand in power increased, resulting in excessive Joule heating in co-linear chamber, which along with flow stagnation at walls and recirculation-stagnation areas at the outlet of treatment zone, resulted in a higher temperature increase. Steinmetz design experienced flow circulation regimes downstream of treatment zone. These circulation areas posed no hindrance to flow inside the treatment zone due to their positions at top and bottom of the channel, but instigated thermal hot spots because of presence of high electric fields, while parallel-plate design had most uniform flow behaviour and thus no thermal hot spots were foreseen. The model was validated by comparing predicted and experimentally measured temperatures. Inactivation of Escherichia coli population in all treatment chamber designs, with experimental RFEF system operating under modelled process parameters, was 1 log CFUml^-1.