Week of March 1st- Pressure sensors not working.
March 09, 2010
Monroe suggested using a needle valve after the first attenuator to reduce fluctuations in the pressure readings. Set the valve so that it doesn't cause too much build up of water in the first attenuator. Open the valve all the way so that water is actually going backwards into the first attenuator. Then close the valve until water level in the first attenuator is just rising. The first attenuator should be closed and the second (after the rotameter) should be open to the air. A lot of air bubbles were getting into the system when the second bottle was closed.
1. Full Flow Experiment #1: 8mL/min - 380mL/min, 1 hr. Process Controller Method: (N://AguaClara/CDC/Spring 2010/Rotameter/RampedFlow).
Result: The data fit an equation for orifice flow through a 0.09in orifice with a 2cm offset for the pressure.
March 10, 2010
1. Preliminary Low Flow Experiment: 8mL/min - 40mL/min, 1hr.
Same setup and process controller method (N://AguaClara/CDC/Spring 2010/Rotameter/RampedLowFlow ) as with the Full Flow Experiments except used a different range for flow rates).
Result: The data not consistent. There were too many fluctuations in the pressure and can't determine any relationship between flow rate and head loss. Monroe suggested re-doing the experiment using a smaller tube for the peristaltic pump.
March 11, 2010
Pressure sensors not working again. Monroe determined the cause was the ANC group's pH probes. The probes were sending high voltages to the system. He grounded the water so there would be zero voltage water going through the pH probe. He also switched the voltages on module 0 and module 1 so that now the low voltage is on module 0 and the high voltage is on module 1. The system reads from module 0 first, then module 1 and then circles back. This way, at least module 0 will be read. The pressure sensors use low voltages while the pH probes use high voltages.
1. Full Flow Experiment #2: 8mL/min - 380mL/min, 1 hr. (Same Process Controller Method as before.
Result:
(The first experiment was run on 3/9/10.) The data seems good, but didn't fit the 0.09in orifice line as well as the first experiment. This run also showed a linear increase in head loss with flow rate at the lower flow rates. Not sure what the cause of that is.
2. Low Flow Experiment #1: 8mL/min - 40mL/min, 1hr.
New Process Controller Method (N://AguaClara/CDC/Spring2010/Rotameter/RampedLowFlow).
Same set up as before EXCEPT now using tubing size =16 to reduce the fluctuations in pressure I n the Preliminary Low Flow Experiment (3/10/10).
Result:
The data suggests that there is a linear relationship at the lower flow rates. However, it seems like the linear portion ends at a lower flow rate than with the full flow experiments. We will redo the experiment to verify this.