Modeling the heat and mass transfer and pressure buildup during the microwave drying of food-porous material

ARBALLO J.R; CAMPAÑONE LAURA A.; MASCHERONI R.H

Conferencia; Comsol Conference; 2014

In the recent years the microwaves has been used in the food processing industry as a result of the advantages with respect to conventional treatments: less environmental impact related to the use of clean energy and low energy consumption and short processing time, and saving in location space. In the food industry their uses include: thawing, pasteurization, sterilization, heating, blanching, cooking, baking and drying. The above mentioned advantages are due to the microwaves have the ability to penetrate and heat within the materials. The microwaves are propagated in the form of an electromagnetic field that interact with the polar molecules (mainly water molecules) of the irradiated material and generate initially its heating. When the microwave heating progresses, promotes the water vaporization and the removing inner water is enhanced by increasing water-vapor pressure and forcing the vapor toward the surface. With respect to increasing temperature it is necessary to obtain the absorbed microwave power inside the material due to the interaction between electromagnetic field and food. The Maxwell?s equations describe the electromagnetic distribution inside the microwaves ovens, empty or loaded. Nowadays, two modeling lines have been followed to predict the distribution of electromagnetic energy inside the food: solving the Maxwell?s equations or the use the Lambert?s Law which is an approximate description, which considers an exponential decay of the energy inside the food material. With the purpose to gain a better understanding about those complex phenomena involved in the microwave drying process it is necessary to obtain a complete model and simulate the process under various conditions. To model the changes in temperatures, moisture content and inner pressure during the microwave drying of food material is necessary to solve the mass, energy and momentum balances. Theses balances with their boundary conditions form a system of nonlinear partial differential equations that are highly coupled. Due to the complexity of the equations system it is necessary the implementation of a numerical technique, in the present work it will be used the finite element method (FEM). A complete and complex model was obtained and simulated using the commercial software COMSOL Multiphysics® that implements the numerical methodology.