Mathematical modeling and computer simulation of simultaneous heat and mass transfer during drying of food particles
Cinar, Inci Dogan
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The purpose of this dissertation was to design and simulate a mathematical model for the process of simultaneous heat and mass transfer during fluidized bed and tunnel drying for both thawed and infused rabbiteye blueberries. Two different simulation models, namely the diffusional and Luikov models, were formulated and solved using a finite element method (FEM). Blueberries were considered as homogenous pieces and modeled using spherical geometry.|Moisture and temperature distributions in both blueberries during either tunnel or fluidized bed drying were described by a set of coupled non-linear heat and mass transfer equations. Non-linearities in these models were introduced by the use of moisture or temperature dependent transport parameters and material properties.|The Luikov model considered both liquid water and vapor diffusion whereas the diffusional model assumed only liquid water transfer and surface evaporation.|The finite element formulation was developed using Galerkin’s weighted residual technique. Numerical solution of these models took into account non-linearities. Coupling effects, which improves the predictions, were presented in governing equations and boundary conditions.|Simulation data was verified by the experimental drying data for both thawed and infused berries in tunnel and fluidized bed dryers. Initial moisture content of thawed berries was 578.99 kg water/100kg DM and of infused berries was 127.87 kg water/100kg DM. Tunnel drying was done at 60 o C with air velocity of 4 m/s and 0% relative air humidity. The temperature of the fluidized bed dryer was 170 o C for thawed berries and 150 o C for infused berries with an air velocity of 12 m/s and relative air humidity of 0%.|The Luikov model gave better approximations to the moisture distribution due to its ability to account for the vapor diffusion.