Numerical estimation of the effective moisture diffusivity during microwave heating of food

摘要

The objective of this work is to develop a numerical model that allows the estimation of the effectivemoisture diffusivity and the mass transfer coefficient at the surface of food products exposed to microwaveradiations. The model does not require the resolution of Maxwell’s equations and closed-form expressionsare used to compute the microwave energy dissipated inside the food due to dielectric heating. An inversemethod is used for the parameters estimation and a numerical procedure is fully developed. The mass transferequation for moisture and the closed-form expressions for the microwaves are coupled to the heat transferequation via a finite elements scheme. The methodology is first tested with fictitious experimental dataobtained from numerical results to which random noise is added. Based on the numerical results, thedistribution of moisture content within the sample is also discussed. Numerical results show that the moisturecontent gradient at the end of the process is mainly influenced by the value of the moisture diffusivity.Experiments of microwave heating are finally carried out on a sample inside a waveguide. The evolution oftemperatures during the heating is first used to determine more accurately the power absorbed by the sample.The final moisture distribution is then used to estimate the effective moisture diffusivity and the mass transfercoefficient. The study constitutes a preliminary step in the development of a more accurate model. It showsthe relevance and the limits of the inverse methodology applied to the determination of diffusionmechanisms.