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It is important to take a look at the effect of Reynolds number on the results as water treatment plant built by AguaClara varies geographically. The flow rate into water treatment plant is different for different location. Reynolds number is changed by changing the inlet velocity boundary condition. The normal flow rate is of Reynolds number of 10,000. From figure 12, it is seen that the pressure coefficient drop changes only a little with big changes in Reynolds number. In other word, the pressure coefficient drop is not sensitive to the Reynolds number of the system. This is a good thing because in the design of flocculator, the flow rate of the geographical location can be neglected. One set of flocculator design can be used for different flow rate.
Figure 13. Clearance Height Effect on Pressure Coefficient Drop and Maximum Velocity
By adjusting clearance height, the effect on the pressure coefficient drop was also analyzed. It can be seen that the pressure coefficient drop is independent of the change in clearance height as long as the clearance height is greater than a certain critical value. Figure 13 shows that after a critical value of 1, the pressure coefficient drop is constant. This phenomena can be explained using figure 5. Figure 5 shows the clearance height of 0.15 m. However, from 0.1 m onward, the flow is mostly stagnant in the flocculator. This mean that 0.1 m is needed for the flow to navigate through the turn and after this point onward, there is not much activity happening. Clearance height of less than 0.1 m gave higher pressure coefficient drop as it created a constriction of flow and the frictional loss was increased. With this result, it is recommended for the design team that the clearance height must be at least the same of bigger than the baffle width to produce predictable pressure coefficient drop.
Figure 14. Comparison of Turbulent Dissipation Rate for Clearance height of 0.1 m and 0.15 m.
To further validate that the result is not sensitive to the change in clearance height, the contours of turbulence dissipation rate of clearance height 0.1 m and 0.15 m was compared. The result showed that the region of active turbulent dissipation was the same, about two times the length of baffle spacing. With this result, it is concluded that the design team has the freedom of choosing clearance height according to their design constraint and not theoretical constraint as long as the clearance height is greater than the baffle spacing.
Figure 14. Effect of Turbulence Model on Pressure Coefficient Drop
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