The influence of bends on liquid-liquid flow through reduced dimensions

The present study aims to investigate the effects of bends on the hydrodynamics of toluene-water flow in a 2 mm diameter conduit. A comparison with results in a straight tube of the same diameter reveals that the incorporation of bend has a significant influence on flow pattern and pressure drop. They retard the heavier phase (water) to a greater extent, thus promoting the formation of water bridges which favours slug flow and inhibits the annular flow pattern. The bend orientation and angle also influences both flow pattern and pressure drop. Since the 45° bend causes a greater change in momentum as compared to 90° bend, the pressure drop is higher in the former case. The effect of bend has been quantified by the loss co-efficient and amplification factor. Both the parameters vary inversely with mixture Reynolds number and are independent of flow patterns. Since slug flow leads to enhanced transport characteristics while annular flow has the reverse effect, the results suggest that the mere introduction of a bend can effectively serve the purpose of process intensification in reduced dimensions. The best results can be expected when a 90° bend connects a short horizontal to a longer downflow section. Nevertheless, the accompanying increase in pressure drop needs to be considered in evaluating the economy of this technique for process intensification.