Experimental study of flow transitions in structured packed beds of spheres with electrochemical technique

In the past years, structured packed beds have been attracting more attention due to their special performances and potential applications. In this paper, the flow transitions are experimentally tested with electrochemical techniques in three different structured packed beds, including simple cubic (SC), body center cubic (BCC) and face center cubic (FCC) packing forms, which would be investigated for the first time and some interesting results are obtained. The microelectrodes are placed at the tube wall and inner particle surfaces to test the local flow fluctuations at the pore level, with particle Reynolds number (Re) ranging from 20 to 1100. According to the analysis of fluctuating rate (FR), three different flow regimes in the packed beds, including laminar, transition and turbulent flow regimes are identified. It is found that, the flow transition in SC packed bed is later and that in FCC packed bed is earlier, considering both the end of laminar flow and onset of turbulent flow when compared with those obtained in random packed beds. For SC packed bed, the transition flow regime occurs at Reynolds number ranging from 260 to 430 for most electrodes. For BCC packed bed, the end of laminar flow occurs at about Re ≈ 130, the onset of turbulent flow of inner probes occurs at about Re ≈ 350 and that of tube wall probes at about Re ≈ 580. For FCC packed bed, the transition regime covers a range of 70 < Re < 250 for most electrodes.