The Influence of the Geometric Properties on the Gas Holdup and Phase Surface Area for Single-Orifice Gas Distributors in a Bubble Column

The introduction of a gas phase into a liquid is used in a variety of technical applications. Based on the purpose of the application, different flow behaviors of the gas phase and specific gas phase parameters are preferred. In this study, the influence of the diameter and shape of a single-hole orifice sparger on the gas phase behavior was investigated. For this purpose, an experimental setup of a bubble column was built, and different orifice sizes and types were installed. The two different designs that were tested were direct flat orifices and single needle-type nozzles. The flat nozzle diameter was varied from 0.5 mm to 3 mm, whereas two different needle-type nozzles with diameters of 0.5 mm and 1 mm were also tested. Through high-speed imaging and digital image processing, a contour analysis of the bubbles was performed using a special technique for image segmentation and the identification of phase inhomogeneities. The gas holdup and surface area of the gas phase were calculated at different column heights and different flow rates. The results show that smaller nozzle diameters led to a higher gas holdup and a higher phase surface than larger-diameter orifices at the middle and upper sections of the column, implying a better mass and heat transfer performance.