Effect of orientation of chain-like agglomerated particles on pressure drop in solid-liquid flow systems

The effect of orientation of chain-like agglomerated particles on the pressure drop has been studied experimentally by using the electro-rheological fluid. By means of two types of test sections generating the electric fields perpendicular (= cross flow type) and parallel (= parallel flow type) to the flow, increments of pressure drop by the agglomerations were measured. The obtained pressure drop increment by the cross flow type was almost 3 times higher than that by the parallel type when the concentration of particles, fluid Reynolds number and electric field intensity were the same. In order to explain the main cause of the agglomerations orientation, we proposed a model in which the pressure drop induced by the agglomeration is assumed to be equivalent to the energy consumption by the breakage of the chain-like agglomeration in the unit volume. Based on this model, the ratio of the increment of the pressure drop of the cross flow type to that of the parallel flow can be deduced as the ratio of the numbers of agglomerations. The number of the agglomerations was estimated by the force balance between the adhesive force of the particles and the drag force induced by the flow through the fibrous layer. In the force balance, we took into consideration the effect of the orientation of the force. This model could explain the effect qualitatively. This fact implies that the effect of orientation can be considered as the effect on the drag force of fibrous agglomeration layer and the force direction, depending on the agglomerations orientation.