|Title:||Liquid distribution and structural changes during convective drying of gels|
|Authors :||Kharaghani, Abdolreza|
|Published in :||Colloid process engineering|
|Publisher / Ed. Institution :||Springer|
|License (according to publishing contract) :||Licence according to publishing contract|
|Type of review:||Editorial review|
|Subject (DDC) :||660: Chemical engineering|
|Abstract:||Experimental and three-dimensional numerical simulation studies on convective drying of gels are presented in this chapter. As a physical model of a real gel, highly porous particle aggregates are produced by sintering of glass beads inside a graphite mold. A lab-scale X-ray microtomograph is used to perform a series of drying experiments with loose packings of sintered glass beads (mean diameter 700 μm) initially saturated with water. The reconstructed images (voxel size 16 μm) are analyzed to obtain the time evolution of the solid, liquid, and gas phase distributions during convective drying. A computational tool based on the volume-of-fluid approach is developed to simulate the liquid distribution over time at the microscopic scale in this model particle aggregate, which is subjected to convective drying. The simulated liquid phase distributions are found to be in good qualitative agreement with the experimental results. The major physical effect of capillary flow from large pores into small pores is easily recognized: large pores dry out first while small regions of the void space stay saturated with liquid. In addition to these pore-scale studies, resorcinol-formaldehyde (RF) hydrogels are synthesized by sol-gel polycondensation of resorcinol (R) with formaldehyde in the presence of sodium carbonate as a catalyst (C). The mechanical effects (cracks and shrinkage) in RF gels with three different R/C ratios and three different aging times are studied. The results show that the degree of shrinkage drastically increases with decreasing R/C ratio and also that the degree of shrinkage is slightly reduced by longer aging.|
|Departement:||School of Engineering|
|Organisational Unit:||Institute of Computational Physics (ICP)|
|Publication type:||Book Part|
|Appears in Collections:||Publikationen School of Engineering|
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