We are given a U-tube, a few tubing connectors, an air pump and a length of silicone tubing. The objective of this Practical is to build an air-lift pump to transfer 500-ml of water from one vessel to another.
1. What is an air lift pump? How does it work?
An air lift pump is a device that uses compressed air to lift water from a well or sump. This pump is also referred to as a mammoth pump.
The working principle, compressed air is mixed with water in an air lift pump. We know that the density of water is significantly greater than the density of air. Air, which has a lower density than liquid, rises quickly due to buoyancy. The liquid is drawn into the ascendant airflow by fluid pressure and moves in the same direction as the air.
2. Materials Used
A) Experimental Setup
B) During Experiment
Roles & Responsibilities
Running of Experiment
C) Experiment Data
Experiment 1
Experiment 2
D) Questions & Tasks
1. Plot tube length X versus pump flowrate. (X is the distance from the surface of the water to the tip of the air outlet tube). Draw at least one conclusion from the graph.
2. Plot tube length Y versus pump flowrate. (Y is the distance from the surface of the water to the tip of the U-shape tube that is submerged in water). Draw at least one conclusion from the graph.
3. Summarise the learning, observations and reflection in about 150 to 200 words.
During Experiment 1, we tested 5 alternative locations for a, while maintaining the height of b is 10cm constant. We observed that a height increases, the flowrate decreases.
During experiment 2, we held a is 2cm constant while altering the height of b. We observed that as the b height increases, the flowrate decreases. This is because the tube is near the top of the cylinder which means that it is near atmospheric pressure causing the vacuum pressure to decrease.
Due to covid-19 heightened measures, the practical have to conduct at home. Therefore, one person that is Qusyaie has to be the experimenter. We all meet on the time during the meeting and we communicate very well with each other but we still prefer to do it face-to-face as we all get to try to run the experiment.
4. Explain how you measure the volume of water accurately for the determination of the flowrate?
For experiment 1. Our team uses a jug that has read at the sides. Since the experiment said we need a 5L jug, we filled the jug until the 5L line. Then we proceed to record in 3 separate timing (30s,45s,60s) and at each different tube height within the U-tube pipe(2cm, 4cm, 6cm, 8cm and 10cm). After each allocated timings, we then use the timings and multiply it with the different tube height respectively which will give us the flowrate and also the average flow rate at each tube height respectively.
For experiment 2. Our team uses a jug that has read at the sides. Since the experiment said we need a 5L jug, we filled the jug until the 5L line. Then we proceed to record in 3 separate timing (30s,45s,60s) and at each different U-tube height (10cm, 12cm, 14cm, 16cm, 18cm, 20cm). After each allocated timings, we then use the timings and multiply it with the different tube height respectively which will give us the flowrate and also the average flow rate at each tube height respectively.
5. How is the liquid flowrate of an air-lift pump related to the air flowrate? Explain your reasoning.
As the liquid flow rate increases, airflow rate also increases. This is because it uses the same formula Q=V/T which is volume divided by time. Which is then converted to V1T1 = V2T2 (the continuity equation)
6. Do you think pump cavitation can happen in an air-lift pump? Explain.
Yes, because the jug has a maximum point and as we placed the U-tube pipe in the jug the base height of the U-tube pipe and the surface level of the water is the suction head. As the height of the U-tube pipe increases near the surface level of the water, the NPSHA is decreasing causing the air lift pump cavitation as the NPSHA<NPSHR.
7. What is the flow regime that is most suitable for lifting water in an air-lift pump? Explain.
Turbulent flow. As the air lift pump started its operation, water was laminar and turbulent at the same time. This is because the air bubbles from the pump are forcing the water up in the U-tube pipe in the sampling port. This requires a lot of energy from the pump and hence, the regime of the water is turbulent.
8. What is one assumption about the water level that has to be made? Explain.
It has very low efficiency, only 20 to 40% energy available in form of useful water and very difficult to give a wide range of flow control by varying the volume of compressed air.
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