Finite element modeling of continuous-flow microwave heating of fluid foods and experimental validation

In this study, heating of fluid foods in a specially designed continuous-flow microwave heating unit (915 MHz and 5 kW maximum power) was simulated by finite element method using COMSOL Multiphysics. Experiments were then conducted with different test fluids (distilled water, 0.5% and 1% CMC solutions) at different flow rates (1, 2, 3 L/min) to validate the model. The pilot-scale unit consisted of a PTFE tubing which was helically configured within cylindrical cavity of the unit. Cross-sectional temperature distribution at the exit of the tube was measured by specially designed thermocouple system at thirteen points. Numerical and experimental results showed that heating was more uniform for distilled water in comparison to CMC solutions at all flow rates. A comparison of the results of this study to the literature showed that more uniform heating can be achieved for high-viscosity fluid food products by using helical tube in continuous-flow microwave heating systems.