Comparative studies of heat and mass transfer by convective and microwave-convective drying for nonhygroscopic ceramic
Drying is a complex process as it involves a lot of mechanism and material process particular heat and mass transfer that evolves concurrently during the process. In a simple word drying can be defined as removal of water or moisture from any porous substances. Drying may be accomplished by convecti...
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| Main Authors: | , |
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| Format: | Article |
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AENSI Journals (Australian Journal of Basic and Applied Sciences)
2014
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| Subjects: | |
| Online Access: | http://eprints.uthm.edu.my/8272/ http://eprints.uthm.edu.my/8272/1/Comparative_Studies_of_Heat_and_Mass.pdf |
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| Summary: | Drying is a complex process as it involves a lot of mechanism and material process particular heat and mass transfer that evolves concurrently during the process. In a simple word drying can be defined as removal of water or moisture from any porous substances. Drying may be accomplished by convective heat transfer, conduction from heated surfaces, by radiation or by dielectric heating. Different drying technique also will result in the different structure and properties of the dried or sinter body since moisture removal has strong correlation with shrinkage, packing porous structure as well as pore formation. Thus, understanding drying mechanisms under different drying techniques can help to control failure of the dried product. This aim of this paper is to propose a mathematical model and compare the drying mechanism for both convective and microwave-convective drying for nonhygroscopic ceramic materials. This current work used a coupled mathematical model of mass, heat and gas transfer that embedded with finite element method in two-dimensional domain and numerically computed using Skyline solver to capture highly nonlinear transient process. The model variables which provide analysis of time evolution of saturation, temperature and gas pressure are used to obtain better understanding of the mechanism that occur during the process of drying at fundamental level. Validation of the proposed model shows good agreement with the experimental data and other model results gained elsewhere. The computed results showed effectiveness of the drying process improves drastically in convective-microwave drying when compared to convective drying corresponding to mass and heat fluxes coincide in same direction, where from internal of matrix to the surface material. Thus easier removal of moisture is noted with higher temperature, moisture saturation and gas pressure accumulated at the bottom center of the material. However, the combination of those gradients may also lead to increment in potential internal defects on the dried material. Nevertheless, the increase understanding in fundamental mechanism that occurs during both drying modes is acknowledged resulted from the proposed model. |
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