Friction Loss in a Pipe System: Lab Report

Introduction

The aim of this lab report is to describe how friction losses in a pipe system work, and to conduct an experiment to observe some errors. The primary objective is to demonstrate the change in the laws of resistance from laminar to turbulent flow and calculate the critical Reynolds number. Reynolds numbers are used to determine the type of flow, whether it is laminar (Re < 2000), turbulent (Re > 4000), or in the transition range.

Two flow scenarios were investigated: lower flow and higher flow.

For the lower flow experiment, a header tank was used, while for the higher flow experiment, the test pipe was connected to a hydraulic bench. Measurements of water collection and time taken were recorded for both flow rates. Friction losses in pipes can be categorized into major head losses and minor head losses, which may occur due to bending, contraction, valves, and other factors contributing to friction loss.

This experiment aimed to measure and investigate friction loss in a pipe across a range of flow rates, with a focus on how the friction factor varies with Reynolds number by controlling and changing the fluid's flow rate in the pipe.

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Bernoulli's equation was employed to calculate head losses, which result from wall friction in the pipe and sticky forces between fluid layers.

Materials and Apparatus

Materials:

• Water

Apparatus:

• Stopwatch: Used to measure the time taken for the collected amount of water.
• Hydraulic bench: Used to determine the flow rate of water through various sets of apparatus.
• Needle valve: Used to adjust the pressure.
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• Outlet pipe: The pipe from which water exits.
• U-tube water manometer: Used for low flow rate readings.
• Bourdon gauge: Used for high flow rate readings.
• Beaker: Used to measure the quantity of water produced from the outlet pipe.

Methodology

Higher Flow Experiment:

1. The apparatus was connected to the hydraulic bench by a technician to allow water to flow through the horizontal pipe.
2. The needle valve was fully opened, and the hydraulic bench supply was adjusted to achieve a reading of approximately 2000mm on the Bourdon gauge.
3. A beaker was used to measure the amount of water produced from the outlet pipe.
4. While measuring the water with the beaker, a stopwatch was used to measure the time taken to fill the beaker to a certain volume.
5. A thermometer was placed in the beaker to measure the temperature of the water at each step recorded from the Bourdon gauge.
6. Needle valve was used to reduce the differential roughly every 250mm steps, ensuring at least 9 steps of results, and data collection stopped at 2000mm differential. The differential and flow rate were recorded at each step.

Lower Flow Experiment:

1. The apparatus was connected to the header tank by a technician, providing a source for water flow through the horizontal pipe.
2. The needle valve was fully opened, and the differential head of around 450mm on the water manometer was carefully adjusted and recorded.
3. A beaker was used as a collection and measuring vessel, and a stopwatch was used to measure the time taken to collect a suitable quantity of water from the outlet pipe. The temperature of the collected water was measured with a thermometer.
4. Needle valve was used to reduce the differential roughly in 30mm steps, aiming for at least ten steps of results, with data collection stopping at around a 30mm differential. The differential, flow rate, and water temperature were recorded at each step.

Results and Calculations

Lower Flow

Higher Flow

Discussion

A clear transition is observed in the lower flow results of this experiment. The flow of a viscous fluid can be either laminar or turbulent, depending on the velocity. Low velocities correspond to laminar flow, while high velocities indicate turbulent flow. The critical factor is the Reynolds number, which determines the transition into turbulent flow and the breakdown of laminar motion.

If the Reynolds number is less than 2000, the flow is laminar; if it is greater than 4000, the flow is turbulent, and if it falls between 2000 and 4000, it is in transition. The discrepancies in collected results and values during the laboratory work can be attributed to errors that may have occurred during the experiment.

Three types of errors were encountered during the experiment: apparatus errors, personal errors, and natural errors. Apparatus errors may result from incorrect setup by the technician, such as improper pipe connections. Personal errors, including incorrect readings from the manometer in the lower flow rate, can significantly affect the final calculations. Additionally, issues with the stopwatch, such as a broken start/stop button, influenced the accuracy of time measurements. Lastly, a lack of sufficient knowledge among students may have led to various experiment-related errors.

To improve the experiment's accuracy, students should gather more information before the lab session and strive for precision in all tasks. Awareness of potential errors and careful execution can contribute to more reliable results.

Conclusion

The critical value represented by the Reynolds number serves as the criterion for the transition from laminar to turbulent flow. This lab report aimed to describe the operation of friction losses in a pipe system and shed light on errors that may affect the experiment's accuracy. The primary focus was on investigating friction losses in a small bore horizontal pipe across a range of flow rates.

References

1. University of Toronto (no date), Writing Advice (The lab report). Available at: http://advice.writing.utoronto.ca/types-of-writing/lab-report/ (Accessed on 11/12/2018)
2. Frictional loss in pipe (2016) Available at: https://studymoose.com/frictional-loss-in-pipe-essay (Accessed on 13/12/2018)
3. Lab report flowmeter measurement apparatus (2015) Available at: http://www.academia.edu/18747069/CHE241_-_Lab_Report_Flowmeter_Measurement_Apparatus_FM101_2015_ (Accessed on 14/12/2018)
4. Friction loss in a pipe (no date), Available at: https://www.tecquipment.com/friction-loss-in-a-pipe (Accessed on 18/12/2018)

Appendix

Abbreviations:

• H: High
• M: Moderate
• L: Low

Control Measures:

• Ensure the wheels of the hydraulic bench are locked.
• Test for electrical safety or perform a pat test on tangy wires.
• Avoid standing on wires and remain vigilant.
• Prevent slip hazards by avoiding standing in water and cleaning it when necessary.
• Exercise caution while adjusting the pressure circle.
• Wear ear protection to mitigate exposure to machine noise.
• Wear safety gloves and robes to protect against splashing water.
• Regularly monitor water for Legionella bacteria hazards.
• Exercise caution when checking the header tank to prevent falls.