Numerical and experimental analysis of heat and moisture transfer of Lavandula x allardii leaves during non-isothermal convective drying

Abstract

In the present work, an experimental and numerical study is performed for describing the unsteady heat and moisture transport occurring in Lavandula x allardii leaves during non-isothermal drying, for time-varying temperature profiles. Drying experiments were conducted in a laboratory-scale convective dryer for an initial temperature level of 40 °C, ramping up to 60 °C at different temperature advancing rates under a constant airflow velocity of 2 m/s. A simultaneous heat and mass transfer model under a nonconjugated approach is proposed for leafy products, considering conduction and liquid diffusion among the inner layers of leaves. A computational algorithm was developed to predict the temporal and spatial changes of temperature and moisture during processing. Numerical results were validated with the experimental dehydration curves. The proposed modeling approach was found adequately fast and accurate for simulating the non-isothermal drying process of herbal leaves and can be further utilized for product-specialized dryer design, control or process optimization. • Non-isothermal drying regimes are applied on Lavandula x allardii leaves. • Effects of linear drying temperature increase on drying kinetics, are evaluated. • A simultaneous heat and mass transfer model is used to study the drying process. • Temporal and spatial changes of leaves' temperature and moisture are predicted. • Numerical results were in a good agreement with experimental dehydration curves.