Winter 2024 Department of Civil and Environmental Engineering CE 362L Experiment 1: Pipe Flowrate Measurement Introduction The purpose of this experiment is to calibrate two types of flow-measuring devices (orifice meter/nozzle meter and Venturi meter). Students will determine the coefficient of discharge (Co) to quantify the viscous effects that contribute to minor head losses as a fluid moves through each device. The performance of these devices will then be compared to explore how their geometry governs the nature of the observed losses. Each student will upload a completed worksheet in Canvas before the deadline. Theory Recall that the Bernoulli Equation describes the energy balance along a streamline for a steady, inviscid, and incompressible flow: P₁ V₁² +Z₁ Y 2g + = 2 P₂ V2 + +Z₂ γ 2g (Equation 1) Where is the specific weight of the fluid. The elevation of the point relative to some constant datum is given by z, P is the pressure, and V is fluid velocity. The Continuity Equation provides further means to compare the fluid flow at two points using mass balance: V₁A₁ = V2A2 Where A is the cross-sectional area of the flow. (Equation 2) These two principles are the foundation upon which orifice, nozzle, and Venturi meters operate. Each device is designed to measure the pressure drop that results across a reduced cross section due to the increase in velocity needed to conserve mass (see Section 8.6 in your book). Substitution of Equation 2 into Equation 1 gives an expression for the flow rate as a function of the measured pressure: 2g 20 Qideal = A2 P₁-P2 + (Z-Z2) γ 1. A₂ A₁ 1/2 (Equation 3) 1 Winter 2024 Department of Civil and Environmental Engineering CE 362L Equation 3 gives the flowrate under ideal conditions (those where viscosity can be assumed negligible). The actual value is somewhat smaller, and the degree to which is a function of the device's geometry and the properties of the flow. An empirical constant, often termed the discharge coefficient (Co) is used to capture this effect: Qactual = CoQ ideal (Equation 4) Co can reach values as low as 0.6 and must be determined by experiment (the purpose of this lab): ე = Q actual Qideal (Equation 5) Once a value of Co is determined the device can then be used to measure the flow rate through a pipe with a high degree of accuracy. Part I: Venturi Meter Procedure 1. Record the cross-sectional area at the inlet and throat of the venturi meter. Ensure that the downstream valve is partially closed. Turn on the pump. 2. Adjust the flow rate using the main valve such that the pressure head at these locations is within the range of the attached manometers. 3. Record the flow rate and manometer measurements at the two locations for a total of five (5) flow rate values. From supply Manifold Hand Pump Venturi 2 Air valve Manometer tubes To measuring tank Winter 2024 Department of Civil and Environmental Engineering 4. Turn off the pump. Figure 1. Venturi meter apparatus 3 CE 362L Winter 2024 Department of Civil and Environmental Engineering CE 362L From supply Inlet pipe Part II: Orifice/Nozzle meter Procedure 1. Record the cross-sectional area of the orifice (or nozzle). Turn on the pump. 2. Adjust the flow rate through the tank using the main valve and wait for the system to reach a steady state. 3. Record the flow rate through the tank and the pressure measurements indicated by the attached manometer. 4. Repeat steps 2 through 4 for a total of five (5) flow rates. Turn off the pump. 5. Share the results of this part of the experiment with your classmates so that each group has data for all orifice/nozzle types. Top plate Manometer To drain Adjustable feat Tank Diffuser Overflow pipe Orifice Pitot assembly To weigh tank Figure 2. Discharge through orifice apparatus Winter 2024 Department of Civil and Environmental Engineering CE 362L Hydraulics Lab 1 Worksheet Name: Please write or type answers to the following questions in the space below or on separate paper. Attach tables and figures as requested. Turn in the completed packet as a single pdf file uploaded to Canvas by the deadline. 1. Attach a table or tables with data from your lab. Include measured data provided, actual flowrate (Qactual) and calculated values of Qideal and Co. 2. Attach one plot with all Co values versus flow rate (distinguish each meter from the others in some way). 3. Which 'meter' had the greatest Co? Explain why. Describe how the differences in the design of each meter contribute to variability of Co. 4. Describe the trend for each meter. Are your results similar to fig. 8.40 in the textbook? Note that the range of Reynolds numbers in fig. 8.40 is probably greater than that for the experiments. L