Analysis and Design of Direct Steam Injection for Tomato Concentrate Sterilization

Direct steam injection is a sterilization technique which is often used for high-viscosity fluid food, when the preservation of the quality characteristics and energy efficiency are the priority. In this work, an apparatus for the sterilization of tomato concentrate has been analyzed by means of a 3D computational fluid dynamics (CFD) model, in order to optimize the exchanger performance in terms of temperature distribution inside the product. A multidimensional two-phase model of steam injection inside a non-Newtonian pseudoplastic fluid was adopted to evaluate the thermal history of the product and the condensation rate of the steam injected in the heat exchanger during the thermal process. Subsequently, the CFD analysis has been extended to examine the effects of the different process parameters (sterilization temperature, steam flow rate, radial and axial temperature profiles and nozzle geometry) on the resulting product. Results obtained allowed to understand the effects of process parameters on the behavior of the condensing steam and obtain better performance of the exchanger in terms of temperature distribution of the treated product.