Dr. David Israel Posadas Navarro

Universidad Nacional Autónoma de México
México

Abstract Title: On Characterization Hydrodynamic of a Mixed Flow Impeller by Particle Image Velocimetry Technique

Biography:

David Israel Posadas Navarro completed his PhD in 2022 year from the Autonomous National University of Mexico. At the moment, is a student postdoctoral in the same university. He has published papers in Chemical Engineering journals such as Chemical Engineering and Technology, and Chemical Engineering Research and Design. He is an expert in the use of techniques for flow visualization such as Particle Image Velocimetry (PIV), and Planar Laser Induced Fluorescence (PLIF).

Research Interest:

Gas-liquid agitation systems are essential in various biological applications, especially in microorganism cultures. Traditionally, the Rushton turbine impeller is used for gas-liquid mixing, but it has limitations such as dead zones and inadequate pumping capacity. To overcome these issues, a hybrid impeller called an axial-radial impeller (ARI) with four paddles was developed. This impeller combines tilted blades a 45 degrees and straight blades to generate a mixed flow. This impeller demonstrates superior performance to the traditional Rushton turbine because generates a more uniform flow through the tank. In the present work, Particle Image Velocimetry (PIV) was used to assess the impact of the paddles' number on the local hydrodynamics of the original design of the ARI impeller (4, 5, and 6 paddles) in a cylindrical tank filled with water, rotating at 300 rpm, and with an airflow rate of 2 L/min. Results are reported in terms of vertical currents and strain rates. Results indicated that the three ARI impellers produced significant downdrafts and updrafts. However, the four-paddle ARI generated a more uniform flow, which enhanced mixing efficiency and reduced mixing time. On the other hand, as expected, the highest string rates for all sets of impellers tested were generated near the blades. However, the ARI with 6 paddles creates a better distribution of strain rates through the tank. As a consequence of the above, the ARI with 6 paddles will have a better broke of bubbles, which implicates an improved mass transfer capacity. In conclusion, the investigation revealed that increasing paddle count enhances the break of bubbles, and as a consequence of the above increase of mass transfer of original design, although it doesn't necessarily decrease mixing time. The ARI presents a promising alternative for fermentation processes, emphasizing the need for further optimization of its design to maximize hydrodynamic performance.

keywords Hybrid impeller, mixing, PIV, stirred tank, visualization flow