Performance Parameter Approach in Determining Optimal Geometry
To determine the optimal geometry, performance parameters, εθ, ε^(1/2)θ, ε^(1/3)θ, K, and Gθ, have calculated for each baffle for flocculation tank heights of .2, .3, .5, and 1. These performance parameters are extracted from the results of the converged solutions for the geometries listed above using the attached UDF.
*Note that eps_1/2 values for H/w of 3,5,10 are normalized by the flow (x100).
Pi Cell Analysis
The region of high energy dissipation behind a baffle can be categorized by estimating by pi cell value (the length of the region in terms of the width in between baffles). Interestingly with larger flocculation tank heights the pi-cell values highlighted in the charts above continue to increase.
From observations of the energy dissipation regions in tall (h/w >5) flocculation tanks, the energy dissipation regions do not interact with the separation region at the subsequent region. Thus, it seems reasonable to conclude that there is a maximum pi-cell value that would be constant with increasing pi-cell values. However, in the formulation of this quantity, the energy dissipation from the entire baffle is summed (including energy dissipation from the walls), and thus the increasing flocculation tank heights results in increasing pi-cell values.
Below is a chart which shows the pi-cell values as a function of the height:
Performance Based Analysis
From the data, observations about the values of the performance parameters can be made:
- The Gθ/m^2 value decreases with increasing flocculation tank height indicating that the most efficient flocculation occurs at a h/w ratio of 2. This type of trend would be exhibited for εθ, ε^(1/2)θ, and ε^(1/3)θ if they were normalized by area.
- Similarly, larger pressured drops, K for both observed and calculated are exhibited for flocculation tank with smaller heights. This reflects how energy dissipation regions intersect with each other.
- Large flocculation tank heights have a more uniform performance over all baffles, and reach a converged baffle solution more quickly than the smaller flocculation tank heights.