EXPANSION OF STARCH DURING THERMAL PRESSURE FORMING
Advancing the chemical engineering fundamentals
Transport Phenomena in Porous/Granular Media (T2-7P)
Keywords: starch, thermal forming, finite element method, mold filling, expansion
The contribution is aimed to the processes of thermal treatment of starch-based materials for biologically degradable packaging products. The combined heating of starch-based suspension (direct ohmic heating and thermal processing of starch based suspensions) was performed in a closed mould. The sample expands significantly (approximately 3 times) during heating and this expansion is accompanied by gradual formation of crust and a porous layer in the core. The time course of the sample expansion was detected by a grid of thermocouples and compared with the recorded pressure inside the mold. The mathematical models of the combined ohmic heating of starch suspension was formulated. The finite element model is based upon the concept of two overlapping 2D meshes: the fixed mesh represents the heating plates and the crust, while the moving (expanding) mesh describes the expanding core (foam). The foam behavior is modeled according to the idea of expanding spherical bubble, filled by a saturated steam and with viscoelastic walls. Besides the finite element model also a simplified model of a homogeneous sample (expanding homogeneous foam) will be presented. Parameters of models are identified by comparing the theoretical predictions with the experimental data.
Presented Monday 17, 13:30 to 15:00, in session Transport Phenomena in Porous/Granular Media (T2-7P).
