An adaptive/conjugate finite element approach to drying of porous single/multiparticle systems
Abstract
An adaptive finite element methodology for the analysis of coupled transport problems was successfully developed and implemented. The methodology was based on the use of an estimator to evaluate the magnitude the finite element solution error. An error norm, based on the definition of the energy norm for transport equations, was used in the error estimation procedure. The information obtained from this procedure was then used to calculate the size of the elements in the adapted mesh. The error estimator took into account the effect of convective-type boundary conditions on the solution error. Applications included the study of simultaneous heat and mass transfer during drying of a wood board and a brick. Results from the adaptive analysis were compared to results from conventional finite element analysis available in the literature. A finite element methodology for the analysis of conjugate heat and mass transfer in the convective drying of hygroscopic porous media was also developed in this study. In this methodology, the interface between porous medium and external convective flow is treated as an internal boundary within a two-phase system rather than a geometrical limit. The problems of solid drying and convection boundary layer are connected by expressing the continuity of the state variables and their respective fluxes through the interface. The performance of the proposed methodology was evaluated by applying it to drying of wood boards and single/multi-body systems. The analysis of the drying of porous media as a conjugate problem allowed the assessment of the effect of the heat and mass transfer within the solid on the transfer in the adjacent fluid, providing a good insight of the complexity of the transfer mechanisms. Results showed that there was significant variation of both heat and mass fluxes along the surfaces of the drying media studied here. Significant variation of the heat and mass fluxes with time was also observed. Interesting phenomena were observed regarding the effects of interactions of closely spaced particles on the heat and mass transfer rates of multiparticle systems. The downstream kernel of a two-soybean kernel arrangement achieved higher average temperature than the lead kernel at twenty minutes of drying.
Degree
Ph.D.
Advisors
Haghighi, Purdue University.
Subject Area
Agricultural engineering|Mechanical engineering|Food science|Wood|Technology
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