Determine effective moisture diffusivity of non-isothermal drying process of shrinkage material

Drying is a dehydration process that can help to prolongate storage time, improve product quality, and reduce transportation cost. Although being applied for food processing for a long time, the drying process still needs to be further investigated for optimizing the dryer design and operations. Among the thermal physical properties of food material, the effective diffusivity of moisture is an essential input parameter for drying process calculation. This parameter is traditionally estimated by fitting the drying curve with the mathematical solution obtained from the isothermal drying process for a non-shrinkage material. Hence, the predicted moisture content and temperature evolutions over time deviate significantly compared to the experimental observation. In this paper, the moisture diffusivity is computed using the inverse method. Firstly, a diffusion drying model, in which the material shrinkage is accounted for, was developed. The effective moisture diffusivity was obtained via an optimization routine where the deviation between the numerical and experimental moisture content profiles is minimized. This methodology has been applied to estimate the diffusivity of carrots during classical and ultrasonic-assisted convective drying. The results indicated that the experimental observation can be accurately predicted by the numerical result.