Study on mass transfer in large-aspect-ratio micromixer with continuous dual splitting and recombination, and inclined ridges

Abstract

Micromixers are critical components within microfluidic systems, known for their outstanding mass and heat transfer capabilities. However, during the scale-up, micromixers with large width-to-height aspect ratios (AR) demonstrate minimal variation in specific surface area, which results in a negligible impact on heat transfer efficiency, but a noticeable decline in mass transfer performance. This study introduces a novel micromixer design, the large-aspect-ratio micromixer with continuous dual splitting and recombination, and inclined ridges (CDSARR). To assess the distribution of component mass flow during fluid splitting within channels of varying AR, a new parameter is introduced: component distribution uniformity (CDU). For the CDSARR micromixer, the CDU values at the end of the first-order sub-channels consistently exceeds 0.75 when 0.001 ≤ u ≤ 0.3 m/s and 3 ≤ AR ≤ 4, indicating favorable conditions for further splitting. Conversely, in the large-aspect-ratio micromixer with continuous dual splitting and recombination (CDSAR) under medium and low Reynolds number (Re), CDU values at the end of the first-order sub-channels are consistently below 0.40, leading to suboptimal component distribution and poor mixing efficiency. The integration of inclined ridges within the first-order sub-channels effectively mitigates component distribution issues during subsequent fluid splitting, while their addition in the second-order sub-channels enhances mixing by expanding the contact area post-recombination. Across the Re range of 1 to 200, the CDSARR micromixer exhibits a mixing index that surpasses that of the CDSAR micromixer, maintaining a relatively superior value, especially at low Re, with only a negligible difference in pressure drop between the two micromixers. A evaluation of the comprehensive performance reveals that the CDSARR micromixer offers stable and consistently lower running cost compared to the CDSAR micromixer.