Experiment 2

Experiment 1 

b = 10cm 

a (cm)	X (cm)	Flowrate (ml/s)			Average Flowrate (ml/s)
		Run 1	Run 2	Run 3
2	15	12.80	12.60	12.50	12.63
4	13	11.50	11.60	11.30	11.47
6	11	8.20	8.10	8.30	8.20
8	9	3.40	3.60	3.10	3.37
10	7	2.60	2.10	2.50	2.40

Flowrate is volume of water collected/transferred divided by time taken 

Experiment 2 

a = 2cm 

b (cm)	Y (cm)	Flowrate (ml/s)			Average Flowrate (ml/s)
		Run 1	Run 2	Run 3
10*
12
14
16
18
20

Flowrate is volume of water collected/transferred divided by time taken 

*This is the same setting as the first run in experiment1. You do not need to repeat it. Just record the results will do. 

1. Questions & Tasks 

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.  

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.  

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

We have learned about the working mechanism of an airlift pump. We also have observed that the lower the U-tube sits in the bucket, the easier it for the air to push the water up, and the flow rate will increase. We have also observed the deeper the hose is pushed into the U-tube, the lower the amount of water is pushed out of the U-tube, thus having a lower flow rate. It is also observed that the deeper the hose, the faster the flow rate. 

Explain how you measure the volume of water accurately for the determination of the flow rate? 

We turn on the pump for about 30 seconds to allow the pump to run at full capacity, we then collect water in a measuring jug for another 30 seconds. To measure the flow rate, we divided the amount of water collected by 30.  

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

The higher the liquid flow rate, the higher the airflow rate. As the flow rate of air increases,  the faster the air can push the liquid up, hence increasing the liquid flow rate of the airlift pump as well. 

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

I think that cavitation cannot occur in an airlift pump. This is because the air-lift pump uses air power to push the liquid up. This means that the air-lift pump is air-powered, unlike the centrifugal pump which uses the impeller to push the liquid. Therefore, cavitation can only occur in a centrifugal pump, not in an air-lift pump. 

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

Slug flow regime. The larger particle sizes are more suitable for the air bubbles to lift.

 

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

One assumption about the water level that has to be made is that it is constant throughout the whole experiment so that the pressure applied by the water is the same.