Mixers serpentine

Mixer 27 [M 27] Y-type Micro Mixer with Extended Serpentine Path... 

Mixer type 3-D L-shaped serpentine micro Long and short axis of L-element 700 pm, 400 pm... 

This chapter focuses on fluid flow, leaving the combination of fluid flow, heat transfer, and diffusion to Chapter 11. Examples of fluid flow include entry flow into a pipe, flow in a microfluidic T-sensor, turbulent flow in a pipe, time-dependent start-up of pipe flow, flow in an orifice, and flow in a serpentine mixer. The examples demonstrate many of the techniques that are useful in the program FEMLAB. 

Figure 10.25. Mesh used to model the serpentine mixer.

The chapter begins by listing the equations and the boundary conditions available in FEMLAB. The hrst example is simple heat conduction in a two-dimensional region, followed by applications to microfluidic devices, viscous dissipation in orihce flow, and diffusion in the serpentine mixer. 

To illustrate what is possible in 3D, consider the serpentine mixer that was modeled in Chapter 10. The idea is that at the inlet there are two streams entering, and one of them contains a different chemical. The objective is to mix the chemicals in as short a distance as possible. Because mixing by diffusion is slow, chimneys and turns are inserted to enhance the mixing and make it occur in a shorter distance. This was solved by Zachery Tyree when he was a senior chemical engineering student at the University of Washington (Neils et al., 2004). 

This chapter illustrated the use of FEMLAB for problems of heat conduction, heat conduction and convection, and mass diffusion and convection. Problems included heat conduction in a 2D plane, several microfluidic devices (T-sensor and serpentine mixer), and heat effects in orifice flow. Specific methods demonstrated in FEMLAB include ... 

Figure 7.6 Serpentine mixer used for the generation of eluent gradients with LC EOF pumps. (A) Inlet of serpentine mixer displaying two distinct fluid flows (B) non-uniform fluorescent intensity profile along the channel cross-section (C) outlet of serpentine mixer displaying the fully mixed flows (D) equalized fluorescent intensity profile along the channel cross-section.

Fig. 7.8 Moving droplet mixer. Two aqueous solutions were injected into immiscible oil in a serpentine channel 28 pm wide and 45 pm deep. Flow is from left to right [104. ...

A serpentine mixer (Fig. 8.18) can be used to mix two chemicals in a shorter length than happens in a straight channel. Figure 8.19 shows a typical solution for a Reynolds number of 1.0 and Peclet number of 1000. Comparing these data with those for a T-sensor (Fig. 8.17) shows that the total length/width necessary has been reduced from 250 to 19.6 when the variance is 2.6 X 10". ... 

Table 8.4 Variance at different points in a serpentine mixer.

Another aspect of the serpentine mixer is to define how much mixing occurs for a given pressure drop. The flow solution gives the pressure drop and the variance gives the mixing. Table 8.4 shows results at different velocities for the serpentine mixer. 

Fig. 13 Micromixer combining SAR and chaotic advection approaches (a) Serpentine laminating micromixer (SLM) and (b) concentration contours along the mixers channels, (Reproduced from [131] by permission of The Royal Society of Chemistry), (c) Staggered overlapping crisscross micromixer (SOC p-mixer) and (d) corresponding cross-section view showing concentration profiles after flowing through two junctions (Adapted from [132] with permission. Copyright lOP Publishing)...

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