Laboratory #1 - Supplemental Guide (1)

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4312

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Mechanical Engineering

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Apr 3, 2024

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ME 4312 - Thermal and Fluids Laboratory | Page 1 of 4 The University of Texas at San Antonio (UTSA) Klesse College of Engineering and Integrated Design Department of Mechanical Engineering ME 4312 - Thermal and Fluids Laboratory Laboratory Assignment # 1 : Analysis of Pumps in Series and Parallel Configurations Supplemental Guide Experimental Procedures: The descriptions presented below are supplemental of the descriptions presented in the condensed manual. The switch in Figure 1 is the mains isolator switch. There are two of these switches. The one on the left of the apparatus powers pump 1, as well as the pressure sensors and readouts. This switch should be on for the duration of the lab. The switch on the right of the apparatus powers pump 2 and should only be on when testing series and parallel pump configurations. Figure 1. Mains isolator switch. Before starting any pump, make sure to zero out the pressure transducers (Figure 2). There is also a button to zero out the torque input on both motors. These should also be pressed before starting the motors attached to the pumps. To start the motor, press the green button (at left), and stop it with the red button (at right) shown in Figure 3. The black knob controls motor rotational speed in RPM and is very sensitive. For all tests, you need to run the motors at 3,000 RPM (or as close as 3,000 RPM as possible). If you get within +/- 10 rpm you can record your results as long as you note your exact measurement of rotational speed in RPM. Figure 2. Zero out pressure transducers. Figure 3. Motor controls. Before actually running each experiment, you will need to turn the speed controls on the motors you are using for the current test to max RPM. You will look at the pressures in the system to determine if the system is properly bled. On the two motor control panels, you can find the expected pressure readings for each pump configuration (see Figure 4). The actual pressures should match these values (see Figure 5); if they don’t, let your TA know so they can prop erly bleed the system.

ME 4312 - Thermal and Fluids Laboratory | Page 2 of 4 Figure 4. Expected pressure readings. Figure 5. Actual pressure readings. The outlet valve in Figure 6 should be handled slowly and with both hands. It is PVC on PVC and does have a tendency to bind because of this. For the single, series, and parallel tests this valve should be closed in 0.1 bar increments (read as pressure P4). This should be done up to 1.5 bar (again, read as pressure P4). DO NOT EXCEED 1.5 BAR WITH THE OUTLET VALVE! Figure 6. Outlet valve. Due to inappropriate handling of equipment by students in the past, part of the inlet valve for pump 2 broke off. This part was responsible for limiting how far the valve can be opened. To avoid further damage to the valve, stop opening the valve when the threads on the shaft are flush with the end of the pipe, as shown in Figure 7. Do not do as in Figure 8. The inlet valves require many turns to fully open or close. Figure 7. Good way to open valve. Figure 8. Bad way to open valve.

ME 4312 - Thermal and Fluids Laboratory | Page 3 of 4 Theoretical Data: Theoretical formulations and information can be found in: (1) the lab manual, and (2) your notes from Measurements & Instrumentation, Fluid Mechanics, and Thermodynamics I (review the course schedule for information on textbook chapters). An additional source of information is presented below: https://www.youtube.com/watch?v=iDRoSxZKKz8 Summary of Findings: The following is a checklist of what should appear in the “data analysis” section of your report. None of this information is new or different from what was asked in the manual. It is simply included here in a list with some clarification based on common questions. Your “data analysis” section should be written in report form, not as responses to the checklist. The checklist should be used only to guide your discussion. Steps: 1. Table similar to Table 2 on page 39 (last page on PDF file) of the lab manual for each of the following: a. Single pump b. Parallel pumps c. Series pumps a. Data for ΔP 1 , P 2 , P 3 , P 4 are provided for you. b. Data for pump mechanical power input, W, (and for the second pump where applicable) are provided for you. For two pumps, you must calculate the total power input as the sum of the individual power inputs. Make sure to avoid mixing nomenclature (W 2 is the hydraulic power of the pump). c. Data for pump rotational speed (N) is provided. Note that although the speed was set to 3,000 RPM (revolutions per min), small deviations were recorded. d. All other values should be calculated using equations on pages 25 – 28 of the lab manual. e. As stated in the video, make sure to take a look at Venturi dimensions on page 15 of the lab manual (page 13 on the PDF file) when determining flow rates. f. PAY CLOSE ATTENTION TO UNITS! 2. Summary tables for each of the tables created in Step 1 that will help you see the relationships and compare/contrast the different pump configurations. a. In the summary tables, include flow rate, efficiency, total head, and total input power for 3 flow rates (columns should appear in this order) b. The 3 flow rates should be the following: i. minimum flow rate. ii. flow rate at max efficiency (if the max efficiency is at an endpoint, use an approximate midpoint for the 2 nd flow rate.) iii. maximum flow rate. 3. For each pump configuration, construct a single plot of efficiency, total power input, and total head against flow rate. a. Flow rate will be on the x-axis. b. Axes should appear as shown in the example plot below. c. Plot labels should match your table labels. d. For more information on how to create secondary axis on Excel plots, see the following link: https://support.microsoft.com/en-us/topic/add-or-remove-a-secondary-axis-in-a-chart-in-excel-91da1e2f-5db1- 41e9-8908-e1a2e14dd5a9

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ME 4312 - Thermal and Fluids Laboratory | Page 4 of 4 4. Discuss tables and plots by answering the following questions in your discussion: a. For the single pump test, describe the relationship between efficiency, head, and flow rate. b. What is the best efficiency for the single pump? c. Compare the results for the series and parallel pump tests against the single pump test at the same pump rotational speed. d. Use your summary tables to compare the different tests. For example, compare the flow rates at which the maximum efficiency occurs. e. What can you observe about flow rate, total head, and efficiency among the different tests? The efficiency of large industrial pumps is normally about 75%. Why is the efficiency of the pumps in this experiment different from that of a large industrial pump? Discuss specific reasons.