Pressure Testing

Objective

Obtain a better understanding of the pressure needed to operate your water filter.

Equipment / Supplies

Your water filter, pressure transducer and data acquisition system, tubing and fittings, pump, stop watch, beakers.

Method

Experiment 1 - System Curve (Note: gravity water treatment devices cannot be tested as described below, see the instructor)

The purpose of this test is to identify the relationship between pressure and flow for your water treatment device. Measure the flow rate and related pressure change (before and after water treatment device). This will allow us to compare water treatment devices (e.g., which has the least pressure change for a given flow rate).

Connect pressure transducer and associated tubing/fittings to water treatment device and water faucet.

Set flow rate to about 10% of manufacturer's claimed flowrate.

Record your data acquisition channel. Start data acquisition system. Record time (Computer clock), flowrate (L/min), and pressure change (psi) through filter in your lab notebook. You will use the time and data acquisition channel to find your results in the data file recorded by the data acquisition system.

Repeat 6 to 9 times for various flowrates and pressures, up to the manufacturer's claimed flowrate or until the systems starts to leak excessively.

Using the data recorded in your lab book, find each "mini-experimen"t in the data acquisition electronic file. Determine the average and standard deviation of the pressure change for each flow rate. Record the number of pressure data points for each flowrate.

Calculate the average Power needed to operate the water treatment device at each flowrate.

Plot Flow rate on the X-axis and Pressure change on the Y-axis. Include error bars (95% confidence intervals) for Pressure change. In another figure, plot Flow rate on the X-axis and average Power on the Y-axis. Include error bars (95% confidence intervals) for Power.

Experiment 2 - Clogging

Identify the relationship between pressure and clogging for your water treatment device. Measure the pressure change (inlet to outlet of filter) as you pump a constant flow of dirty water. This will allow us to compare water treatment device (e.g., which takes the longest to clog).

Connect pressure transducer and associated tubing/fittings to water filter and peristaltic pump.

Using clean water, set flow rate to less than 50% of manufacturer's claimed flowrate. You want it to be low enough that you will be able to run the filter for ~1 hr before it clogs. There's no way to know this ahead of time, so just use your best judgment.

Measure turbidity (NTU) and apparent color (Pt-Co) of untreated water.

Record your data acquisition channel. Start data acquisition system. Starting pumping untreated water through your filter. Regularly record time (computer clock), turbidity (NTU) and apparent color (Pt-Co) of the treated water, flowrate (L/min), and pressure change (psi) through filter in your lab notebook.

Continue pumping dirty water until you treat an amount equal to the manufacture's claimed capacity or the system starts to leak excessively.

Using the data recorded in your lab book, find each mini-experiment in the data acquisition electronic file. Determine the average and standard deviation of the pressure change at each measurement point. Record the number of pressure data points at each measurement point.

Find the cumulative volume of water treated at each measurement point. Do this by assuming flow rates over appropriate periods (easy if your flow rate stayed constant) and multiplying the flow rates by the time change.

Plot Cumulative volume of water treated on the X-axis and Pressure change and Flow rate on the Y-axis. Include error bars (95% confidence intervals) for Pressure change. On a separate graph, plot Cumulative volume of water treated on the X-axis and Turbidity and Apparent Color on the Y-axis.

If your data are unacceptable, you will be expected to repeat experiments outside of normal class time.