| Summary: | 碩士 === 中原大學 === 化學工程研究所 === 93 === Many fluid hydrodynamic problems frequently occur when the fluid flows through the particle bed in solid-liquid separation procedure, and this procedure is widely applied in the biochemistry technology. The deformation behaviors of deformable particles are deeply concerned when the deformable particles under mechanical loading and hydraulic drag in particles bed. It is important to study on the particle deformation behaviors, but, still now, there is not a complete theory to refer to, especially in the hydrodynamic behaviors of fluid flowing though the particle bed composed of deformable particles.
Therefore, this study focuses mainly on the experimental phenomenon observation and concentrates primarily on the hydrodynamic behaviors of fluid flowing through the particle bad composed of deformable particles. The Ca-alginate particle with viscoelastic property is used as a test material. A number of in stiu of different experimental conditions such as the entrance flow rate, the initial height of bed, and the strengths of deformable particles could help surveying the variations of the pressure drop, porosity, flow rate, bed height, and the correlation between these variations and that of time, which are to be discussed to seek the reasonable empirical equation of pressure drop when the fluid flows through the deformable particle bed.
Experimental results show that the deformation dramatically influences the results of deformable particle bed behaviors. When the deformable particle is under the different intensity and loading, the constant proportion of Equilibrium Strain varies with time. And the progress decreases gradually in the particle bed height (porosity) while the stress on the bed is increased, with the particles being deformed into polyhedron on the bottom of bed. The more strength the deformable particles get and the more height the particle bed is, the bigger variation of the pressure drops occurs, and vice versa. The variation comes mainly from the distortion degree of the deformable particle itself. The effect of particle deformation due to cumulative friction drag on the reduction of porosity is studied to examine how this variation leads to increase in test. Results indicate that as the skin layer closing to the filter medium formed by the deformable particles, it exhibits a rapid increase in flow resistance and decrease in porosity due to deformation.
The local hydraulic pressure distribution presents a linear relation in local liquid pressure distribution of rigid particles aspects, because the rigid particle shape remains unchanged. Thus, the bed body structure is nearly unchanged. The local hydraulic pressure is the same at any site. Because the Ca-alginate particle can deform itself, the hydraulic pressure distribution presents a curve tendency. The uneven stress of deformable particle causes its height of the bed to concentrate on the bottom of the bed. Apparently, the resistance becomes the biggest and the partial porosity is the smallest at the bottom of the bed.
When fluid flows through the particle bed, the viscoelastic property of Ca-alginate particle rises with time as the pressure drops slowly. The Ca-alginate particle displays a transient behavior. The particle bed regains slightly of its original spherical shape upon releasing of stress after the flow rate reaching the maximum operating flow rate. The hysteresis behavior of the deformable particle can be verified.
To summarize the above results, we know that the most apparent factors of hydrodynamic behavior to influence the particle bed are the size and source of external force function, the deformation characteristics of the particle itself, and the time effect.
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