Practical 2

 Hello peeps. This week we carried out an experiment we were assigned called the air-lift pump challenge. we were required to contract the set up with provided equipment. 

Here is our equipment and experimental setup 

Here are the results we obtained from the experiment

Experiment 1

b = 10cm, Y=16.5cm

a (cm)	X (cm)	Flowrate (ml/s)			Average Flowrate (ml/s)
		Run 1	Run 2	Run 3
2	14.5	5.93	5.80	5.71	5.81
4	12.5	4.20	4.13	4.23	4.19
6	10.5	2.82	2.63	2.60	2.68
8	8.5	1.39	1.11	1.93	1.47
10	6.5	0.39	0.37	0.39	0.49

Experiment 2

a = 2cm, X=14.5

b (cm)	Y (cm)	Flowrate (ml/s)			Average Flowrate (ml/s)
		Run 1	Run 2	Run 3
10*	16.5	5.93	5.80	5.71	5.81
12	14.5	2.89	3.78	3.20	3.29
14	12.5	1.35	1.35	1.20	1.3
16	10.5	0.19	0.19	0.18	0.19
18	8.5	0	0	0	0
20	6.5	0	0	0	0

we used an estimated flowrate of 0 as t water was barely being pumped out. it took too long to collect 100ml of water and it was not feasible for the experimenter to hold the tube for so long.

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.

When the distance from the surface of the water to the tip of the air outlet tube, X increases, the flowrate of the pump increases.

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.

When Y, the distance from the surface of the water to the tip of the U-shape tube that is submerged in water, increases, the flowrate of the pump increases. When Y decreases  below 8.5cm, the water flowrate will be zero, indicating that no water is being pumped out.

3. Summarise the learning, observations and reflection in about 150 to 200 words.

Our hypothesis is that when X increases, the flowrate will increase while when Y increases, the flow rate will increase. For the experiment, we can conclude that flowrate will increase as X increases and the flowrate will increase as Y increases, thus confirming our hypothesis. We learnt that in order to have the highest flow rate, the distance between the water surface in the U tube and the tip of the air tube should be the longest. This will form a laminar flow upwards which will carry a lot of water.

However, after doing the experiment, I reflected on the setup of this experiment and realized that it is very hard to make X to a large number as the air tube keeps coming out of the U tube. Therefore it is important to find a balance so that the air tube will not disconnect while still having a good flow rate.

4. Explain how you measure the volume of water accurately for the determination of the flowrate?

The volume of water is collected using a measuring cylinder. Since the water collected contains bubbles, the time was stopped when the surface of the water reaches 100ml in the measuring cylinder as the volume of water in the bubbles is negligible. 

5. How is the liquid flowrate of an air-lift pump related to the air flowrate? Explain your reasoning.

As the air flowrate increases, the liquid flowrate of the air pump will increase. As the air flowrate increases, the rate where bubbles are formed will be higher. More bubbles will carry a greater volume of water up the tube, resulting in a higher liquid flowrate.

6. Do you think pump cavitation can happen in an air-lift pump? Explain.

No. The bubbles will not collapse as the pressure of liquid in the suction (u-tube) cannot be lower than the vapour pressure of water

7. What is the flow regime that is most suitable for lifting water in an air-lift pump? Explain.

Laminar flow regime. As when it is laminar, the flow of the fluid is easier as the bubbles will find it easier to push the fluid up as the fluid only flows parallel in one direction, so liquid will not flow back down and hence laminar flow will give the highest flow rate.

8. What is one assumption about the water level that has to be made? Explain.

The water level will decrease as the airlift pump carries water out the jug. The water level assumed remain the same as time passes. This is to keep the distance from the surface of the water to the tip of the air outlet tube, X and the distance from the surface of the water to the tip of the U-shape tube that is submerged in water, Y constant.