Hello and welcome to our company new hire! There are a few things that you must know how to do and one of them will be covered in this instructable, that being how to calibrate flowmeters. It is crucial that you know how to do this as in order to reliably use bulk-flow measuring devices that rely on the measurement of pressure change, an appropriate amount of calibration must be done. This is possible by determining the flow coefficients as functions of the flow rate in terms of the Reynolds number. However, it is crucial to know that these coefficients are experimentally obtained and then compared with ISO-published values for similar devices. In addition, a paddlewheel flowmeter will also be calibrated.

Supplies

In order to conduct the experiments the apparatus must be obtained, each apparatus consists of a pipe with two different flowmeters(a hydraulic flowmeter and a paddlewheel flowmeter. ) plus a massive weight tank. The hydraulic flowmeter and the paddlewheel flowmeter can be seen in Fig.1. Also, a plan view of the flowmeter locations is shown in Fig.2. It is also important that the LabVIEW software controls the experiment.

-Paddlewheel flowmeter is a Signet 3-8511-P0

Step 1: Procedure

To start the experiment, you must check that the discharge valve is closed. Then, check the levels of mercury in the mercury-water manometer for the hydraulic flowmeter. Make sure that the levels are equal and if not, slowly open and close the two manometer drain valves. If necessary, adjust the central scale between the two sides of the manometer until the reading is zero or no flow.

Now, to calibrate the output voltage from the Validyne differential pressure transducer. First, zero the transducer output on the VFn interface box. When the discharge valve is closed, open the manometer bleed valve labeled "CAL VALVE". This artificially reduces the pressure in one of the manometer lines, and simultaneously takes the reading of the transducer output and manometer levels. (All recorded using the LabVIEW software.) Record five data points, from zero pressure differential to the maximum pressure differential with the bleed valve fully open. Make sure the voltage does not exceed 10V. (If it does ask your instructor for help.)

Step 2: Data Acquisition

Now to the data acquisition. To obtain the data using the hydraulic flowmeter and the Signet paddlewheel flowmeter, first, check the Gain Adjust control of the paddle flowmeter is set to 6.25 turns for P1 and P4, and is set to 3 turns for P3 (shown in Fig.2) Then use the Zero Adjust control to zero the paddlewheel flowmeter output.

Next, open the discharge valve slowly until the valve is fully open, or the allowable manometer deflection is reached. Observe carefully both the Validyne differential pressure voltage and the Signet paddlewheel voltage. Make sure to record both readings when the Signet paddle voltage reading takes on a significant nonzero value.

Once the maximum flow rate is reached, record the manometer, paddlewheel, and flowmeter readings. Make sure to take a weight-time measurement using the LabVIEW software, along with the time-averaged pressure-transducer voltages.

Now, all you have to do is repeat the steps above with successively slower flow rates. The manometer deflections are approximately (0.9)^2delta-h_max,(0.8)^2delta-h_max,(0.7)^2delta-h_max...,(0.1)^2delta-h_max. Record Validyne differential pressure voltage readings and the Signet paddlewheel voltage when the voltage drops suddenly to zero. Also, make sure the mercury in the manometer has become reasonably steady before data acquisition. Repeat this step for 10 data sets.

Step 3: Lab Report

L1:Calibration curve graph

The flow rate and the manometer deflection have been graphed on a linear scale.

L2:Calibration curve on logarithmic scale

The flow rate and the manometer deflection have been graphed on a logarithmic scale.

The data somewhat appears to fall along a straight line which indicates that a power-law relation of the type might apply.

Step 4:

L5:C_d as a function of Reynolds

This graph shows the discharge coefficient Cd plotted with respect to the Reynolds number. It is also plotted using a linear-log scale.

L6: Using the Lab VIEW data obtained for the paddlewheel output voltage it is now possible to plot a calibration curve. (Shown in the calibration curve paddlewheel flowmeter graph). The flow rates are a max of 0.01753 and a min of 0.00088. Converting this to the velocity of the water. We can see that the maximum we achieved in this experiment was 8.24 volts.

Q2: Through experimentation, it is found that the Reynolds number is proportional to velocity and velocity is proportional to flow rate. Therefore, the velocity increases with the discharge coefficient. Thus, the coefficient is not constant with the Reynolds number.

Q4: With the experiment details it was found that the paddlewheel flowmeter was unreliable for extreme values however, generally the paddlewheel flowmeter is reliable because it takes out any uncertainty for human error. Also, it was found that low flow rates would cause the friction to cancel the movement. Therefore it would be more accurate at higher flow rates to a certain maximum. (But no significant inconsistency was found at higher or lower flow rates.)