Dynamic Characteristics of a Single- and a Two-Phase Flow Through Multistage Orifices

Drag reduction plays an essential role in the nuclear industry and has been an area of interest for many researchers. Accordingly, in the present study, an experimental investigation has been carried out on the effect of a drag reducing polymer (DRP) on the flow characteristics through a serial arrangement of flow restricting orifices with different diameter ratios and spacing. Experiments were performed on both single and double orifice arrangements in a 0.0254 m diameter, horizontal acrylic pipe. These experiments were done both with and without a DRP and used a particle image velocimetry (PIV) technique. A water-soluble DRP was used as an example of a synthetic high molecular weight polyacrylamide. The flow using the DRP was characterized by a comparatively smaller circulation zone downstream of the orifice, as well as lower local velocity values. It was found that the pressure drop through the orifice was reduced by approximately 8-22% when a DRP was used. In addition, the percentage reduction in the pressure drop was found to be considerable in lower Reynolds number flows than for higher Reynolds number flows. As well, the reduction in the pressure drop was found to be independent of the tested polymer concentration between 51 and 125 ppm. Moreover, the two-phase pressure drop was greater than the single-phase pressure drop at the corresponding liquid superficial Reynolds number. However, the percentage of drag reduction while using a DRP in two-phase flows was found to be much smaller than for cases with a single-phase flow.