FLOW PATTERNS OF GAS-LIQUID COCURRENT DOWNWARD FLOW THROUGH AN ORIFICE PLATE

摘要

The hydrodynamic behavior of gas-liquid concurrent downward flow through an orifice plate is essential to comprehend the hydraulics of a stacked sieve-plate packing tower. Particularly, estimating whether there is semi-dispersed flow is significant for the heat and mass transfer performance of the tower. This work aims at identifying the flow patterns downstream of the orifice and the most relative factors influencing the flow patterns. Experiments were conducted by means of observation with the gas and liquid superficial mass flux of 6.02-41.16 kg/m2 /s and 31.85-307.29 kg/m2 /s, respectively. Three orifice plates with an equivalent diameter ratio between 0.031 and 0.073, relative thickness between 0.07 and 0.17 were used. Experimental results show that there are three flow patterns, namely, trickling flow, continuous flow, and semi-dispersed flow at different operating conditions. At low gas flow rate, the flow regime occurs to transform from trickling flow to continuous flow with the increasing of liquid flow rate. At a fixed liquid flow rate, the flow regime occurs to transform from continuous/trickling flow to semi-dispersed flow with the increasing of gas flow rate. What’s more, the gas flow rate with which to form semi-dispersed flow decreases with the increasing of liquid flow rate. Besides, with the increasing of the hole-diameter, the semi-dispersed flow becomes easier to obtain. On the contrary, with the increasing of the kinetic viscosity of the liquid phase, the semi-dispersed flow becomes more difficult to obtain. Then, the flow pattern maps which is a plot of gas superficial mass flux vs. liquid superficial mass flux were plotted. Finally, a correlation was presented to estimate the gas superficial mass flux required to form semi-dispersed flow, showing a satisfactory agreement with experimental data. Therefore, the proposed correlation can provide useful guidelines for the analysis and operation of stacked sieve-plate packing tower.