Three-Dimensional Finite Element Analysis of Moisture Absorption in Expanding Alfalfa Cubes

A three-dimensional finite element analysis for a set of non-linear coupled heat and mass transfer equations is presented. Changes in dimensions of the elements during the heat and mass transport processes were incorporated in the finite element model. The model was used to simulate the transient temperature and moisture distribution in alfalfa cubes during moisture absorption. The models consider temperature and moisture-dependent material properties. Moisture absorption tests were conducted in an environmental chamber for different combinations of air relative humidity (70 to 90%) and temperature (10 to 40·C). Simulated temperature and moisture results were compared with experimental data, and related to stability of cubes during storage and transport. Results indicate that there was significant improvement in temperature predictions (by about 2·5·C) but only a minor improvement in moisture predictions (by 0·5%) when volume change was incorporated into the heat and mass transfer analysis. The alfalfa cubes reached the equilibrium temperature within 30 min of exposure to the humid air. The rate of moisture absorption was dependent upon the relative humidity and temperature of the surrounding air.