ANC CONTROL

Design 2010

INTRODUCTION

The Spring 2010 ANC Control team inherited the original apparatus used by the Fall 2009 team. The original design of the apparatus was giraffe-like in shape, with two 1" pipes connected at a 45 degree angle. See Figure 1.
Figure 1

SPRING 2010 DESIGN

In order to address the Hypothesis and also to increase the ease with which the lime is fed, the team chose to redesign the apparatus. By adding a vertical column to the top half of the apparatus, the operator now has access to simply pour the lime in. As the lime travels down the vertical column, the particles will settle in the lower part of the apparatus and/or flow into the diagonal piece, but then settle out before leaving in the effluent.
The vertical column addressed the issue of feeding the lime but in order to address the other hypotheses, the team decided to build two apparatuses: one with all 1" tubes, one with 1" vertical columns and 2" diagonal tubing. By doubling the diameter of the tubing, it divided the flow rate through the diagonal portion by four. This allowed for a lower capture velocity, which attempts to address the issue of lime being lost out the effluent. See Figures 2 and 3.
Figure 2

Figure 3

In designing the new apparatuses, the team made the vertical column taller than the diagonal column to ensure that water would flow out the diagonal column. It was determined that the head loss through the fixtures at the end of the diagonal column would be negligible. However, when the team began running experiments a problem was discovered. At the end of the effluent tube, there was a candy-cane shaped piece that the water flowed through - this was in order to have the water pass over the pH probe properly (see Figure 4). However, because this resulted in a dip of the height of the water, and the water filled up the tube, the atmospheric pressure at the top of the water in the tube forced the water in the vertical column to drop to its same height (see Figure 5).
Figure 4

Figure 5

The team attempted to correct this problem by sealing the top of the vertical column with a cap. This would result in a vacuum in the area about the water level and would allow the water in the column to remain at a constant height (see Figure 6). However, it was not possible to fully seal the cap and having an open vertical column to pour lime directly into was part of the design's attractiveness.
Figure 6

The team instead chose to alter the design by opening the very top of the diagonal column to atmospheric pressure. Doing so allowed for open channel flow in the tube and allowed the height of the water in the vertical column to remain constant, matching the height of the water level in the diagonal column. (See Figure 7)
Figure 7