Introduction: TAM 335 Lab 5 Calibration of Flowmeters
By Dilan Acharya
Step 1: Introduction
This experiment is to calibrate flowmeters, also known as bulk-flow measuring devices. The three types of flowmeters used in this lab are: Venturi meters, orifice-plate meters, and a paddlewheel flowmeter. The values obtained from these devices will be compared with ISO published values for similar flowmeters. Examples of the types of flowmeters can be found above in "Figure 3" and "Figure 4".
Step 2: Procedure
Each lab setup consists of a pipe with either a Venturi or orifice-plate flowmeter and a paddlewheel flowmeter. A weighing tank located in the basement will be used to calculate the volumetric flow rate. If necessary, bleed any trapped air from the supply lines and zero the manometer. Calibrate the Validyne differential pressure transducer. After calibration, slowly open the discharge valve until the maximum manometer deflection is reached or until fully open. Record both the paddlewheel voltage and Validyne voltage readings. Repeat the previous procedure for the following manometer deflections: (figure located above)
The flow coefficient will be displayed as a function of flow rate after the 10 data sets are collected. "Figure 1" located above shows how two separate flowmeters are used to measure the same flowrate. "Figure 2" shows the laboratory setup containing all three stations.
Step 3: Results
The graphs associated with lab report questions 1, 2, 5, and 6 are featured above, respectively.
Question 2: The discharge coefficient is mostly constant over the range of Reynolds numbers tested. The numbers vary between 0.454 and 0.589 which means that there is roughly a 6% difference between the largest value and the average value. The theoretical value of C_d is exactly 1, which is true for ideal fluids. In reality fluids are not ideal, which is why the experimental values for C_d are quite far off from the theoretical value. The experimental values of C_d have a percent error of about 45%. In order to obtain more realistic results for C_d, the fluid must not be viewed as “ideal” and a more realistic discharge coefficient must be chosen.
Question 4: The paddlewheel flowmeter seems to be reliable within certain flow rates. The Signet 3-8511-P0 has a stated velocity range of 0.3-20 ft/s. If the velocity is out of the specified range, the reading given will not be accurate. From the lab data, the paddlewheel flowmeter was more accurate at high flow rates. The last four data points had a fluid velocity below the specified range.
Step 4: Conclusion
This lab effectively demonstrates how to calibrate various flowmeter devices. The devices used in the lab consist of Venturi meter, orifice-plate meter, and the paddlewheel flowmeter. As discussed in the “results” section, the discharge coefficient was fairly constant over the range of Reynolds numbers. The values obtained from the experiment mostly align with the given values, although there is some error found throughout the experiment.