Experimental Study On Flow Characteristics Of Venturi-Annular Microchannel

In recent years,Venturi jet is often used in the process where mass transfer at gas-liquid interface is the rate controlling step.Annular microchannels can greatly improve the macro-efficiency of mass transfer and reaction,and the enhancement of the process is undoubted.Many studies have been done on Venturi and microchannel respectively,but no study on their combination has been found.In this paper,the flow characteristics of Venturi-Annular microchannel were studied systematically.The Venturi jet and annular microchannel used in the experiment are both made of organic glass.The Venturi jet is divided into I,II and III according to the size of throat,which are connected with annular microchannel of the same size to form I,II and III Venturi-Annular microchannel.With water as continuous phase and air as dispersed phase,the flow characteristics of Venturi jet and Venturi-Annular microchannel were investigated and compared.The cavitation phenomenon was observed from the experiments of the single liquid phase of the venturi jet.The pressure drop gradually increased with the decrease of the venturi jet throat size at the same inlet volume.The gas-liquid mixing was found to be poor in the experiments of the gas-liquid two-phase,and the flow state was more consistent with the Rayleigh jet fragmentation doctrine.The suction volume of the venturi jet increased with the increase of the liquid flow rate,and the suction volume of the smaller size venturi was larger at the same inlet volume.The suction volume of the outlet condition under the submerged condition was significantly better than that under the unflooded condition.In the experimental part of Venturi-Annular microchannel,it is found that the gas-liquid mixing is better when the gas-liquid ratio is low.The results show that the total pressure drop in Venturi-Annular microchannels is dominated by the annular microchannel first,then by the combined action of the microchannel and the Venturi,and finally by the Venturi.From the gas-liquid two-phase experiment,we know that the pressure drop is positively related to the liquid flow rate,and has little relationship with the gas flow rate.The characteristic parameters of bubbles in Venturi jet and Venturi-Annular microchannel were measured by conductance probe.The experimental results show that the larger the throat size is,the more the average number of effective bubbles is.The bubble velocity increases with the increase of liquid volume and tends to be stable gradually.The bubble size of Venturi-Annular microchannel decreases with the increase of liquid flow rate,and has little change with gas flow rate.The diameter of the bubbles produced is obviously smaller than that of the Venturi jet.The bubble velocity decreases with the distance from the measurement point to the exit of the gas-liquid jet.the bubble diameter increases.