**4. Conclusions**

concentration is observed at the entrance, but this diminishes toward the end of the discharge slit for inlet velocity equal to 100 μm/s. Thus the mixing process is completed. For inlet velocity lower than 100 μm/s, the mixing completely occurred instantaneously as the fluids enter the discharge slit. For inlet velocity higher than 100 μm/s, the mixing is not complete as distinct color can be seen from the entrance

In short, complete mixing occurred at low inlet velocity, and the mixing is

As mentioned in previous section, the Danckwerts segregation intensity or the so-called mixing intensity is defined with the mean square deviation of the concentration profile of the component *i* in a cross section of the discharge slit. The segregation intensity can be transformed to a value between 0 (completely segre-

In this work, to determine the mixing quality with respect to discharge slit length, the value of mixing intensity is evaluated at every 100 μm of discharge slit position starting from 300 μm where the fluid starts to mix until 4300 μm which is the end of discharge slit. The mixing intensity value against the discharge slit position for both corrugated and straight microchannels at inlet velocity of 10,000 μm/s is plotted in **Figure 9**. The mixing intensity of corrugated microchannel is higher than the mixing intensity of straight microchannel.

*Comparison of mixing intensity between geometric configuration at inlet velocity of 10,000 μm/s.*

incomplete at higher inlet velocity of 100 μm/s for both configurations of

*Concentration profile of straight microchannel for various inlet velocity.*

until the end of discharge slit.

*Computational Fluid Dynamics Simulations*

**3.4 Mixing intensity evaluation**

gated) and 1 (completely mixed) [22].

microchannel.

**Figure 9.**

**112**

**Figure 8.**

This chapter discussed a study of mixing simulation in microchannel. An analysis is carried out to investigate the effect of the changes of inlet velocity toward mixing intensity over the two different microchannel configurations. The simulation results show the visualization of velocity and concentration profiles along the microchannel. A laminar parabolic flow of velocity profile is observed for two microchannel configurations simulated. The concentration profile gave visualization on the mixing process that occurred in the microchannel. Evaluation of the mixing intensity value represents the mixing performance of the geometry structure. It also gave information on the mixing length requirement to achieve complete mixing. The microchannel needs longer discharge slit to achieve complete mixing if high inlet velocity is used. The result showed that inlet velocity has significant effects on the mixing performance which is represented by the mixing intensity in this study. The higher the inlet velocity, the lower the mixing quality. Careful observation on the mixing intensity profiles among geometry configurations shows different trends of mixing intensity between the corrugated and straight microchannels.
