Pulsed electric field (PEF) treatment is a promising novel technique in the field of food processing industry, biotechnology, and environmental engineering. It is based on applying short, high-intensity electric pulses. One of the main components of a PEF treatment system is a treatment chamber, in which the product is exposed to electric pulses. Numerical modeling provides a unique insight into the distribution of the electric field, fluid flow, and temperature inside the treatment chamber, which cannot be provided experimentally. Existing literature is reporting only on stationary state simulations that do not account for the influence of individual electric pulses, but rather employ a time-averaging of the voltage applied to electrodes.
The purpose of the thesis was to build a time-dependent numerical model of a continuous PEF treatment chamber and to validate the model by experiments. The main focus in building the model was to account for the influence of each individual electric pulse.
In the experiments and simulations, three different treatment chambers (smaller and larger parallel plate chamber and co-linear chamber) and different pulse parameters with different values of the volumetric flow of aqueous NaCl solution were used. In the numerical model, the geometry of treatment chambers was constructed in three dimensions, and the applications of electrical pulses, fluid flow, heating of fluid due to ohmic heating, and heat transfer were described.
The model was validated by comparing the values obtained by numerical simulations with the experimentally measured electric current and changes in temperature of the fluid within the outlet of treatment chambers during pulse application. Using the numerical model, an analysis and comparison of the electric field and temperature profiles was made for each treatment chamber. Finally, the model was used to study the effect of different PEF treatment parameters within ranges that could not be performed due to the limitations of the experimental equipment.
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