Modelling and simulation of drying process for ceramic membrane fabrication
For ages, ceramic properties and structure is known for its brittleness and its failure such as cracking and warping. This weakness also relates to the high sensitivity of ceramic to any thermal gradient effects. Therefore, processing steps of green body of ceramic is crucial especially in membra...
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Main Author: | |
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Format: | Thesis |
Language: | English English English |
Published: |
2015
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Subjects: | |
Online Access: | http://eprints.uthm.edu.my/1613/1/24p%20ONG%20TZE%20CHING.pdf http://eprints.uthm.edu.my/1613/2/ONG%20TZE%20CHING%20COPYRIGHT%20DECLARATION.pdf http://eprints.uthm.edu.my/1613/3/ONG%20TZE%20CHING%20WATERMARK.pdf |
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Summary: | For ages, ceramic properties and structure is known for its brittleness and its failure
such as cracking and warping. This weakness also relates to the high sensitivity of
ceramic to any thermal gradient effects. Therefore, processing steps of green body of
ceramic is crucial especially in membrane fabrication that has a multilayer structure to
ensure the efficiency of its applications. Thus, every step of ceramic membrane
preparation and fabrication needs careful control and monitoring to fulfil these aims.
Drying is one of the main problems that is always associated with the cracks and
leakages of the ceramic membrane. In fact, the drying process is one of the longest
steps corresponding to various evolutions of parameters during the evaporation
process. Due to the limitation in experimental or empirical ability to determine the
changes of dynamic critical variables during drying, modelling and simulation seems
to be the right option to determine and investigate these nonlinear and dynamic
variables and will be the focus of this study. This two-dimensional mathematical
modelling approach is able to predict the changes of variables in heat and mass transfer
during the drying process. The governing system of fully coupled non-linear partial
differential equations of the model was derived from a mechanistic approach where
the mass and energy conservation laws are defined for a particular phase into which
Darcy’s law and Fick’s law are substituted. A fully implicit algorithm has been
employed for numerical solution using the finite element method in which the Galerkin
weighted residual method is used in the spatial discretization and a backward finite
difference time-stepping scheme is employed for time integration. The ability of this
improved model is not restricted to a single homogenous layer of hygroscopic and nonhygroscopic
material, but on the novelty to incorporate multilayer heterogeneous
material properties as a membrane structure. A good agreement obtained by respective
validation works suggested that the model development and implementation are
satisfactory. Subsequently, case studies involving single layer and multilayer have
produced reasonable accuracy at all times. The application of the model at various
case studies involves a convective and enhanced intermittent drying mode which
demonstrates the robustness and trustworthiness in predicting and optimising the
drying process. |
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