by the spreading effect of the recirculations, improving the mixing
factor. In addition, for lower diffusion coefficients, these convection
effects are predominant, and therefore, the mixing significantly
increases, as compared to a straight channel. From a practical
standpoint, these Reynolds numbers would correspond to a larger
width of the channel to decrease both velocity and pressure drop.
For Re ) 533, the total pressure drop is 1.5 bar for the zigzag
configuration (0.15 bar for the straight channel). Because the
pressure drop in laminar flow is proportional to (Vh/Dh
2)(¢P µ
(1/Re)(L/Dh)(Vh2/2)), the increase in the width from 100 to 300
ím with conservation of the Reynolds number would lower the
pressure drop by a ratio of 27 (50 mbars for Re ) 533 in the zigzag
configuration still with large depth-to-width ratio). This scaling
effect would also facilitate the recirculation phenomenon by
reducing the damping effect of the walls.