Multiphysics modeling to study a microwave applicator for continuous thermal processing of liquid foods

• Grant number: 24/01519-4
• Support Opportunities: Scholarships in Brazil - Master
• Start date: June 01, 2024
• End date: March 31, 2026
• Field of knowledge: Agronomical Sciences - Food Science and Technology - Food Engineering
• Principal Investigator: Jorge Andrey Wilhelms Gut
• Grantee: Giovanna Milena Borges Hipólito
• Host Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The electrification of industrial heating processes, associated with the use of renewable and clean sources of electrical energy, has the potential to reduce emissions and increase energy efficiency. Microwave irradiation is a promising and commercially viable electro-technology for the food industry. In this context, a microwave applicator for continuous flow heating of liquid foods is under development in a USP/IMT partnership with financial support from FAPESP and CNPq. This equipment will be used in the thermal processing of products such as juices, pulps and milk, replacing the heat exchanger. Volumetric, rapid heating without overheated exchange surfaces has already shown potential in retaining the quality of the processed product. For the design and analysis of a microwave applicator, it is necessary to use multiphysics numerical simulation in order to couple the phenomena of electromagnetism, heat transfer and flow. The main challenge is the homogeneity of heating, as this can compromise the safety of the product and the energy efficiency in absorbing power. To address this challenge, this project aims to develop and validate this multiphysics model in COMSOL (numerical finite element method) based on the prototype developed in the collaboration project (hexagonal cavity, helical flow, power of 6 kW, frequency of 2.45 GHz), through experiments with a model food whose dielectric properties were determined (water added with sucrose, sodium chloride and CMC thickener). When heating the model food, the following will be measured: flow (0.5 to 1.0 L/min), temperatures along the line (up to 90 °C), temperature distribution at the heater outlet, and incident and reflected powers (after tuning to minimize reflection in the cavity). The validated model will allow detailed analysis of the phenomena involved in terms of power absorption efficiency and temperature homogeneity, as well as allowing the fine adjustment of cavity parameters such as angle and rotation of the input waveguide and geometry of the helical applicator tube. Results of this research will contribute to the development of this technology that can benefit small and medium-sized producers.