Etude de l'encrassement lors du traitement thermique du lait entier par effet Joule Direct

Development of alternative technology like direct Joule effect in order to pasteurize and sterilize food products is of great scientific and industrial interests. This paper investigates the links betweenthermal, hydraulic and electric phenomena in relation with fouling mechanism in a Direct Joule Effect heater. The ohmic heater ( , P=15kW)) is composed of 5 flat rectangular cells, 3 cells ensure heating and two (at the extremities) the electrical insulation. In a first step, the wall overheating was investigated with two model fluids (without fouling) in order to analyze and model the temperature difference between wall (electrode) and fluid versus operating conditions. In a second step, the impact of fouling phenomena was studied through experiments based on whole milksterilisation. A heat dissipation coefficient, RhCO was defined and validated to monitor fouling propensity through global electrical and thermal parameters. Finally, a numerical simulation was developed in order to analyze thermal profiles (wall, deposit, fluid) and enabled to explain and demonstrate the "Snow ball effect" of fouling mechanism