Shear induced diffusion (SID) based flow segregation is a technique that can be used for concentration and fractionation purposes, and it has the potential to become an economical and sustainable alternative for e.g., membrane separation. When compared to conventional microfiltration, problems related to fouling and cleaning are expected to be minimal. To make the best use of the opportunities that this technique holds, detailed insights in flow and particle behavior are needed. Modelling this process allows for us to chart particle segregation in flow, as well as the effect of suspension removal through a pore and the restoration of the flow profile after the pore. As a starting point, we take the computation fluid dynamics (CFD) model that is presented in a previous study. A difference in channel height to particle diameter ratio influences the entrance length of the SID profile as well as its fully developed profile. When extracting liquid through one pore, particles are systematically transmitted at a lower concentration (59-78%) than is present in the bulk. The recovery lengths of the SID profile after the pore were short, and thus pores can be placed at realistic distances, which forms a good foundation for further design of this novel separation technology that will ultimately be applied for fractionation of particles taking relatively small differences in diffusive behavior as a starting point.
Experimentally it has been shown that the pores used in the filtration part can be much larger than the particles present in the suspension because the segregation is established earlier while flowing through the closed channel, and only the layer near the membrane needs to be removed [15,17]. To really understand the complexity of shear induced diffusion and use it as a basis for process design, also numerical studies are needed in combination with experimental validation, and quite some information is available. Vollebregt et al. [14,20] and Miller et al. [21] e.g. focused on modelling of concentration profiles of monodisperse and/or bidisperse suspensions in a closed channel, while Lyon and Leal [22,23] and Semwogerere and coworkers [18] focused on experimental verification of this phenomena. Van Dinther and coworkers [15-17] have taken this one step further and applied the principle of shear induced diffusion in a filtration setup similar to the one described in Figure 1.3 for bidisperse suspensions. All these studies have contributed to improved understanding of shear induced diffusion, but especially for the filtration system still a lot of parameters that are essential for process design are unknown. For example pore dimensions and placement, and the effect of polydispersity, still need to be investigated, and are all in the core of the work presented here.
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