Enhanced micromixer designs for chemical applications – Numerical simulations and analysis

Abstract

Microfluidics plays a vital role in managing microscale chemical processes, particularly in reactions with rapid kinetics and exothermic conditions, where laminar flow can result in inefficient mixing. This study investigates the use of simple, cost-effective geometric modifications to improve micromixer performance. Using numerical simulations with a commercial CFD tool, we analyzed the impact of obstacles in an L-shaped micromixer (aspect ratio 10) and the effects of serpentine and zigzag bends in a T-shaped micromixer on water-water mixing. At Reynolds numbers ranging from 1 to 100, we found that the L-micromixer's mixing index slightly increased from 18.7% to 19.3% due to diffusion alone, but adding four specific obstacles enhanced mixing efficiency to 83.7%, demonstrating the significant effect of passive flow enhancement for micromixer with high aspect ratio. Additionally, the serpentine and zigzag micromixers with a turn angle of α = 120° were examined across four configurations, with 2, 4, and 8 pitches. The results demonstrated that increasing the number of pitches reduces the distance required to achieve 99% mixing efficiency. At a Reynolds number of 10, the 8-pitch serpentine micromixer reached near-complete mixing of 98.2 % at x=20 mm, while the 2-pitch micromixer required x=40 mm to reach 97.15%. The 8-pitch zigzag micromixer reached 99.3% at x=30 mm, while the 2-pitch micromixer required x=40 mm to reach a maximum of 81.9 %. The effect of the zigzag micromixer's turning angle, β, was also explored. Increasing β forces the flow through sharper bends, which enhances mixing efficiency, though at the cost of a higher pressure drop. These results also highlight a superior mixing performance of serpentine geometries, offering an effective, low-cost solution for improving microscale mixing in chemical processes.