Reference no: EM133148375
ENGIN1002 Engineering Physics - Fluid laboratories
Laboratory experiment - Pipe Friction
Aim
• To examine the difference between major and minor head losses.
• To examine and compare friction factors for the straight pipe using various flow rates.
• To determine the friction factor from lab results and compare with the literature values.
• Determine the minor loss factor of a component in the pipe network.
• Obtain hands-on experience; appreciation of the use of instruments; data analysis; and comparison of experimental results with theory
Requirements
Construct your own Moody chart and compare it with the Moody chart provided in the lecture slides/textbook. Include the answers to these questions in your report:
• Do your Moody chart and the provided Moody chart give the same value of friction factor, f? If not then why? What type of errors may contribute to this misalignment? Can you quantify the errors?
• If you are to do this lab again to have a better outcome(s) then what are the changes you would apply to the lab procedure?
• If you are to calculate the friction factor, f, by using either the Colebrook-White or Halland equations, do you get the same values provided by the lab results and the Darcy-Weisbach equation? If yes why, if no then why not?
Compare the K-factor of the component you have investigated in the lab with the value you can find in the textbook. Provide answers to these questions:
• Are the values the same? If no then why not? What are the causes of the differences? Can this be quantified or is there something wrong with the lab procedure?
• If you are to improve the lab procedure, what are the changes that you would do to improive the outcome(s)?
Procedure for pipe friction experiment
1. Inspect the apparatus: ensure everything is in working order. Pay particular attention to electrical connections and any water that might be laying around for the risk of electrical shock. (Your lab demonstrator should ask you to complete a HIRAC or other form of Job Safety Analysis before commencing this practical).
2. Establish the pump flow rate: Inspect that all hoses are secured properly and not leaking. Turn on the hydraulic bench pump at a very slow rate. Use the flow control knob to control the flow through the pipes.
3. Calibrate the manometer: make sure that air bubbles are removed from the apparatus. Great care must be taken in doing this as air bubbles will give incorrect measurements from the manometer. With the pump flow rate established, bleed all air from the hoses. All air will be gone from the rig when, under zero flow conditions (turn the pump off or close the valve to the rig), both sides of the manometer must give the same value. This is an important step in manometer calibration. If needed, use the bike pump to pressurise the manometer and move the zero level to about the midway mark of the manometer, as shown in Figure 1.
4. Commence measurements: Open the valve at the end of the pipe very slowly so that only a small flow is released (you want to reach the laminar flow region in the first few measurements). Use the stopwatch and water jug provided to determine a flow rate (measure the volume collected over a desired period i.e., 60 seconds). Measure the pressure difference on the manometer in millimetres. Take note of the water temperature.
5. Complete measurements: repeat the measurements made in step 4 for additional 9-12 flow rates. Only open the valve on the pipe a small additional amount each time to achieve an increase in flow rate. The objective is to increase the pressure difference on the manometer only about 20 or 30 mm at a time.
6. Additional notes: All of the necessary information to construct a Moody diagram must be obtained; use Table 1 below as your guide. An example of the format the Moody diagram must take is shown in Figure 2 below. Data to obtain and calculate includes flow rate (Q), pipe diameter (D), head loss (HL) and water temperature (T). From this information the friction factor (f), Reynolds number (R), and relative
roughness (ε/D) can be derived. Ensure you convert all measurements into the correct units before using them in any equation. A Moody chart from the textbook is also provided in Figure 3
7. Finish the experiment: turn off the pump and make the apparatus safe before leaving the laboratory. Double-check that you have all of the required information to complete your laboratory report.
Laboratory experiment 4 - Open Channel Flow (Continuity)
Aim
• To demonstrate the concept of continuity.
This will be done by measuring two cross-sectional areas of flow within a flume (flow channel), and the total flow rate entering that flume. The average velocity will then be determined. A Pitot-static tube will be used to directly measure the flow speed at the measured cross-sections of flow and compared to other calculations.
• Obtain hands-on experience; appreciation of the use of instruments; data analysis; and comparison of experimental results with theory
Requirements
• Are the flow rates at different measurement points the same? If they are not the same then why not? In your opinion, what may be the cause of this misalignment? Can you quantify the cause/error/issue?
• Do you think the Conservation of mass equation has a flaw? Or do you think the experiment procedure/method needs to be changed or adjusted? What are your proposed changes to the experiment to get a more reliable outcome?
Procedure for open channel flow experiment
1. Inspect the apparatus: ensure everything is in working order. Pay particular attention to electrical connections and any water that might be laying around for the risk of electrical shock. (Your lab demonstrator may ask you to complete a HIRAC or other form of Job Safety Analysis before commencing this practical).
2. Prepare the flow channel: tilt the channel so that is gently sloping in the downstream direction. This can be done using the handle located at the end of the flow channel and the accompanied gauge, as shown in Figure 4 below.
3. Set up the experiment: insert a sluice gate at about halfway along the channel and secure it so that there is about a 20 mm gap (aperture). Or submerge an object to be the flow over the hallway along the channel.
4. Measure the channel width.
5. Preliminary test: turn on the pump to allow water to commence flowing through the channel. Start the flow at a low flow rate and increase flow gradually. Always check that the sluice gate/object is fixed and not moving. Monitor for leaks or other problems that might occur. If any issues are found, switch off the apparatus immediately and notify your staff member in charge.
6. Allow the flow to increase to a rate where water is allowed to "back-up" behind the sluice gate and there is a clear difference in flow depth upstream and downstream of the gate.
7. Once happy with the water level difference, allow the flow to settle and become steady.
8. Record the total flow rate using the "weight of water" method. A stopwatch is available to assist with this.
9. Using the depth gauge, measure the depth of flow at some distance upstream of the sluice gate (about 1m) and some distance downstream of the sluice gate (about 1 m).
Note: If a hydraulic jump occurs immediately downstream of the sluice gate, increase the slope of the channel until the hydraulic jump moves sufficiently downstream. Then record your measurements.
10. You should now have sufficient information to determine the flow speed at the two measured cross-sections upstream, and downstream of the sluice gate, using the equation Q = VA or V = Q/A.
11. Now use a Pitot-Static tube to directly measure the velocity of flow at the same two sections. Make sure that all air bubbles are removed from the probe and any tubing. Air bubbles present within the probe or tubing will lead to inaccurate readings.
12. Insert the Pitot probe so that it is about halfway between the channel bed and water surface.
13. Measure the rise in water level in the pitot tube compared to the water surface of the flow channel. Use this information to calculate the velocity at your point of measurement. Use the equation V = √2gh , where h is the piezometric head.
14. Once all measurements have been made (double-check), turn off the pump to the apparatus, clean up any mess and return equipment to where it belongs.
Note: you may wish to take photographs during the experiment to help you when you write up your report. You may also wish to include photos in your report.
Attachment:- Fluid laboratories.rar