Modeling microwave drying kinetics of Tectona grandis wood using thin-layer models and a power coupled hybrid model

Abstract Mathematical thin-layer drying models are widely employed to characterize moisture loss kinetics and optimization of efficient wood drying processes. Conventional thin-layer drying models describe moisture ratio primarily as a function of drying time and do not explicitly account for variations in microwave power, limiting their predictive capability under different operating conditions. To address this limitation, a power-coupled hybrid model was developed by incorporating microwave power into the drying equation. Drying kinetic studies were performed on Tectona grandis wood under pulsed microwave drying at power levels of 1.6, 2.0, and 2.4 kW. Experimental data were fitted using thin-layer drying models including Newton, Henderson–Pabis, Page, Logarithmic, Two-term, and Midilli models. Model performance was evaluated using coefficient of determination ( R 2 ), root mean square error (RMSE), and reduced chi-square ( χ 2 ). The proposed model demonstrated good predictive performance ( R 2 = 0.995, RMSE = 0.020, and χ 2 = 4.6 × 10 −4 ) and was further validated using independent datasets from Hevea brasiliensis wood, yielding R 2 values between 0.912 and 0.841 demonstrating its broader applicability. Effective moisture diffusivity estimated using Fick’s second law ranged from 4.56 × 10 −8 to 6.51 × 10 −8 m 2 s −1 , which increased with microwave power. Activation energy was estimated as 20.42 kJ mol −1 .