Development of a resonator-based measurement system for characterizing the thermo-dielectric behaviour of corn during microwave drying

Precise control of drying parameters is essential for energy conservation and product quality in industrial agriculture. Addressing the limitations of traditional real-time monitoring, this research developed a novel measurement system based on the Cavity Perturbation Technique (CPT) to simultaneously analyse the drying kinetics and temperature-dependent dielectric properties of corn samples. The system integrates a 2.45 GHz microwave resonator, Vector Network Analyser (VNA) and precision load cell, ensuring high accuracy through Teflon-referenced calibration. Experimental investigations revealed significant dielectric changes as the temperature increased from 20 °C to 80 °C. Consequently, the dielectric constant (ε′), representing energy storage, decreased from 60 to 54.5 and the dielectric loss factor (ε″), representing energy dissipation, decreased from 16.8 to 14.5 due to thermal agitation. Kinetics data demonstrated that mass transfer occurred in the ‘falling rate period’, where internal diffusion was the limiting factor. Theoretical validation using five thin-layer models indicated that the Midilli et al. (R2=0.995, χ2=2.22×10−4) and Page (R2=0.994,RMSE=0.014) models provided the best fit. This innovative methodology offers a reliable, high-precision approach for data-driven process control in microwave drying applications.