Lab 6 Partial Report

This Instructable provides a guide to calibrating and evaluating hydraulic and paddlewheel flowmeters. The purpose is to help a new engineer understand how to use experimental data to develop calibration curves, determine discharge coefficients, and evaluate the accuracy of the flowmeter.

1. Orifice-plate flowmeter
2. Signet 3-8511-P0 paddlewheel flowmeter
3. Mercury-water differential manometer
4. Validyne differential pressure transducer
5. Water supply and piping system
6. Weighing tank and scale
7. Stopwatch
8. LabVIEW
9. Microsoft Excel
10. Lab 6 Manual

This shows the linear plot of volumetric flow rate vs. manometer deflection.

This data does appear to follow a log-log scale relationship.

The rising and falling cutoff velocities were not recorded in this lab, but the maximum velocity was 14.33m/s and the minimum measured velocity was 10.90m/s.

Using the discharge coefficient versus Reynolds number graph from Step 3, we can evaluate whether the discharge coefficient remains constant over the measured range. The experimental coefficients ranged from 3.06-3.19, indicating relatively little variation with the Reynolds number. However, these values are significantly higher than the theoretical value of 1, which are considered normal for an orifice-plate flowmeter. This shift from idealism can be attributed to friction in the flow stream, or flow separation and contraction of the flow stream.

Using the paddlewheel calibration curve from step 4, we can evaluate how accurately the voltage output represents the measured volumetric flow rate. The data shows a strong, positive, linear relationship between the voltage and flow rate. This is demonstrated with an r-squared value of 0.993. This shows consistency throughout the measured range. Thus, the measurements to not show a clear difference in accuracy between high and low flow rates. But in reality, and significantly low flow rates, the paddlewheel may become unreliable due to not enough fluid moving to maintain rotation.