Computational modelling of the transport phenomena occurring during convective drying of prunes

摘要

A mathematical model was developed to describe the coupled heat, mass and momentum transfer pro-cesses occurring in convective drying of prunes. In this model, the fruit is represented as a composite ellipsoidal body comprising of two materials (flesh and stone) having different properties. The model accounts for the variation of both air and food properties expressed as a function of temperature and moisture content. The resulting systems of transient non-linear partial differential equations (PDEs) in the space-time domain together with the set of initial and boundary conditions were numerically solved by utilising the finite element method (FEM) coupled to the Arbitrary Lagrange-Eulerian (ALE) procedure to account for the shrinkage phenomenon using a commercial package (COMSOL Multi-physics~(tm), Comsol AB, Stockholm, Sweden). A series of laboratory drying experiments were undertaken using a computer-controlled dehydration system developed to obtain drying kinetics data under varying operating conditions for validation of the predicted results from the proposed model. Comparison of the model predictions against the exper-imental results has shown a very good agreement, implying that the proposed numerical model can be used with confidence as a tool in optimising the design and operation of the prune drying system. A para-metric study performed using the modelling tool has demonstrated the impact of key operational param-eters on the drying kinetics. It is expected that the model can be applied for other food products and processes involving similar phenomena.