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This lab report contains information about water hammers and how they work.
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LECTURER: Mr V Hashe Date: 17 September 2021
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I MC MBATHA (219007543) hereby declare that this is my original work. All information obtained directly or indirectly from other sources has been fully acknowledged. Furthermore, it represents my own opinions and not necessarily those of the University of Johannesburg.
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E, Modulus of elasticity [GPa] K, Nominal bulk modulus of water [N/m^2 ] A, Area [m^2 ] D, Diameter [m] V, Volume [m^3 ] ฮฝ, Flow velocity [m/s] Q, Flow rate [L/s] C, Velocity of pressure wave [m/s] โฯฐ, Pipe length [m] ะ , Pressure [bar] ฯ, Density [kg/ m^3 ]
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DECLARATION ........................................................................................................................ i ABSTRACT...............................................................................................................................ii NOMENCLATURE ................................................................................................................ iii Table of Contents ...................................................................................................................... iv List of Figures ........................................................................................................................... iv List of Tables ............................................................................................................................ iv OBJECTIVE .............................................................................................................................. 1 INTRODUCTION ..................................................................................................................... 1 APPARATUS ............................................................................................................................ 2 EXPERIMENTAL PROCEDURE ............................................................................................ 2 OBSERVATIONS ..................................................................................................................... 3 ANALYSIS OF RESULTS ....................................................................................................... 3 DISCUSSION ............................................................................................................................ 6 CONCLUSION .......................................................................................................................... 6 RECOMMENDATIONS ........................................................................................................... 6 REFERENCES .......................................................................................................................... 7 LIST OF FIGURES Figure 1: Water hammer (Walsh, 2019). ................................................................................... 1 Figure 2: Pipe surge and water hammer with hydraulic bench. ................................................. 2 Figure 3: Data captured and calculated by the VDAS. .............................................................. 4 Figure 4: Graph 1, analysis of the first volume flow rate value. ............................................... 4 Figure 5: Graph 2. ...................................................................................................................... 5 Figure 6: Graph 3 ....................................................................................................................... 5 LIST OF TABLES Table 1: Data collected. ............................................................................................................. 3 Table 2: Software generated results. .......................................................................................... 3 Table 3: Sample calculations for the data in Graph 1. ............................................................... 3
Figure 2 : Pipe surge and water hammer with hydraulic bench.
Given data: K= 2. 1 ร 109 N/m^2 E= 103 GPa = 103 ร 109 N/m D= 22.2 mm (0.0222m) A= 0.3 87 ร 109 m^2 t= 1. 6 mm (0.0016 m) Table 1 : Data collected. Time delay (s) Distance Travelled (m) Volume flow rate (L/S) 0 1.5 0. 0 1.5 0. 0 1.5 0. Table 2 : Software generated results. Volume flow rate (L/S) Flow velocity, V (m/s) Theoretical pressure rise (bar) Acoustic Velocity (m/s) 0.508 1.312 16. 0.372 0.961 12. 0.352 0.909 11. ANALYSIS OF RESULTS Sample calculations Table 3 : Sample calculations for the data in Graph 1. Parameter Calculations Area ๐ด = ๐๐^2 4 = ๐( 0. 0222 )^2 4 = 0. 387 ร 10 โ^3 ๐^2 Volume flow rate ๐ = ๐ ๐ก =
Figure 5 : Graph 2. Figure 6 : Graph 3
Figures 4, 5, and 6 are graphs that were generated by a Versatile Data Acquisition System to compare the magnitudes of pressure with the theoretical pressure that was also calculated by the VDAS. The table in figure 3 shows the collective data collected by the VDAS. From Graph 1 in Figure 4 it can be seen that the pressure magnitudes are less than 11 bar and the theoretical pressure rise almost reaches 17 bar. The difference between the pressures is more than 6 bar. In figure 5 and 6 the pictures that were taken do not show the exact values of the pressure magnitudes which makes it a bit difficult to analyse the results, but from the observations made in figure 4 it is safe to say that the pressure magnitudes in both the graphs is between 6 to 9 bar. From all the three graphs it can be concluded that the theoretical pressure rise is above the pressure magnitudes. The results that were found may be slightly inaccurate due to some errors that may have occurred during the experiment. Some of the sources of error may be human error which might have occurred when reading the measurements of the volume when measuring the water, or when reading the height on the reservoir. There might have been a calculation error when calculating the volume flow rate which could lead to some minor errors in the results of the experiment. CONCLUSION The water hammer experiment was done successfully. The objectives of the experiment were fully fulfilled, the speed of the pressure surge along the pipe was calculated and the observed magnitudes of pressure were compared to the theoretical results. Even with the minor errors that occurred during the experiment, the speed of the pressure surge was found to be close to the one that was expected to be found when water is at a temperature of 20ยฐC. RECOMMENDATIONS To improve the accuracy and reliability of the results, it is recommended that:
