The synergy angle can be employed t

The synergy angle can be employed to analyze local characteristics of mass transfer in micromixers. However, the vector magnitudes (|U|,|∇u| and |∇C|) are different in the various geometric structures. In order to compare the performance of different micromixers further,the vector dot products in Eqs. (10) and (12) are calculated. Fig. 10(a) shows the relation between U*∇u and Re. As Re increases, the flow resistance increases. The pressure drop of micromixer G-B-G is the highest, which can be verified directly by Figs. 7(b) and 8.Fig. 10(b) indicates the relation between U*∇C and Re. It can be seen that the synergy between U and ∇C in micromixer G-B-G is the best, which is in agreement with Figs.7(a) and 9. According to the field synergy principle, a good synergy between the velocity vector and concentration gradient is beneficial to improve the mass transfer in the micromixers. Therefore, the novel micromixer is effective for mass transfer enhancement.