Experimental study of mass transfer and flow transition in simple cubic packings with the electrochemical technique

Abstract

The electrochemical technique is utilized to test local mass transfer coefficients and flow transition in simple cubic packed beds. The microelectrodes are placed at the tube wall surfaces and inner particle surfaces to study local flow and mass transfer behaviors with particle Reynolds number (Re) ranging from 40 to 1100. The mass transfer coefficients can be obtained based on the limiting current. It is found that, the mass transfer at inner probes is stronger than that of the tube wall probes. Two correlations of mass transfer performance are developed. Mass transfer is enhanced with ordered pore structures in simple cubic packed beds. The effect of tube to particle diameter ratios (N=3, N=4 and N=5) on mass transfer is discussed and no obvious influence is observed. Meanwhile, three different flow regimes in the packed beds, including laminar flow, transition flow and turbulent flow are identified according to the analysis of Fluctuating Rate (FR) of limiting current signals. It is found that the flow transition is largely dependent on the tube to particle diameter ratios. The transition flow regime of SC packed beds covers the range of 260<Re<430 at N=3. The transition flow regime occurs at Reynolds number ranging from 170 to 390 for most electrodes in simple cubic packed beds with N≥4.