Predicting moisture profiles in potato and carrot during convective hot air drying using isothermally measured effective diffusivity

摘要

Temperature and moisture profiles were obtained from potato (1.4 and 2.8 cm diameter) and from carrot core (1.4 cm diameter) and cortex (0.7 cm diameter) during convective hot air drying at 70 ℃ and 1.5 m/s air velocity. These samples represent hygroscopic non-porous materials and remain non-porous throughout drying with porosity remaining below 0.2. To analyze moisture transfer during convective drying, a simultaneous heat and moisture transfer model was developed based on Fick's diffusion equation. What was unique about this model from previous models is that the effective diffusivity and its temperature dependence were obtained from true isothermal conditions and then applied to model the moisture profile during a non-isothermal drying condition. The model accurately predicted moisture loss as a function of drying time and position for the potato and carrot samples during convective hot air drying and further demonstrates the importance and improved accuracy of obtaining diffusion coefficients and its temperature dependence under isothermal conditions.