Week 5 (P2)
Assigned roles
Questions and Tasks
1. Plot tube length X versus pump flow rate. (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 flow rate. (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.
The team have observed that placement of the rubber tubing and u-tube played an important role in the water flow rate. At first we could not even get the water out of the u-tube as the flow rate was too low to exit the u-tube. After thinking, we increased the water level in my pail as we thought that b was way too high for a low water level. At first, we thought that the pump was too weak, however at the end of the experiment, the water level in the pail should also be taken note of as it also affects the flow rate. By doing the experiment and adjusting the measurements by 2cm, we have realised that even a small change in the measurements would affect the results a lot. This is because we could not even get the water to exit the u-tube after giving the measurements a slight change. In this experiment, we have also learnt not to ever give up if the experiment does not show results as we were frustrated at first but we still decided to try different ways to make the apparatus work.
4.Explain how you measure the volume of water accurately for the determination of the flowrate?
I have learnt that measurements and placement of the tubing plays a huge role in water flow rate. In order to measure accurately, I held the measuring cup close to the U-tube to avoid spillage and inaccuracy. Due to lack of appropriate lab equipment for measurement, I used a syringe to measure the access amount of water as my measuring cup only shows markings every 25ml.
5.How is the liquid flow rate of an air-lift pump related to the air flow rate? Explain your reasoning.
Both are related by: When air flow rate increases, liquid flow rate also increases. This is because when the pump is working, it would pump air though the U tube. Hence, when air flow rate increases, there is an increase in pressure at the U tube. This helps “push” the water further up the U shaped tube. Therefore, liquid flow rate increases when air flow rate increases.
6. Do you think pump cavitation can happen in an air-lift pump? Explain.
Cavitation occurs when there is vaporisation of liquid. This happens when the pressure of the liquid at the pump suction is less than the vapor pressure. This would result in vapor bubbles being formed when liquid at pump suction is less than the vapor pressure. Since, there is no liquid flowing at the pump suction, cavitation would not occur.
7.What is the flow regime that is most suitable for lifting water in an air-lift pump? Explain.
The most suitable flow regime is laminar flow. This can be obtained by using Reynold’s number.
We assumed that the density of water is 1000kg/m3and velocity of water to be 0.001kg/m.s. We have also obtained the diameter from measuring the diameter of the u-tube which is 0.012m. We have chosen our flow rate to be 7.43ml/s which is the highest flow rate obtained from this experiment. In order to find velocity, we had to divide the flow rate over the area of the u-tube.
And by using the equation above for Reynold’s number, we have obtained 787.2 which is lesser than 2100, making it laminar.
8.What is one assumption about the water level that has to be made? Explain.
One assumption that has to be made is that the amount of water has to remain constant when water is transferred back to the big jug. This means that water is not lost by evaporation or spillages. This ensures that there is an equal amount of water throughout the experiment.
Photos and videos of experiment
1. Plot tube length X versus pump flow rate. (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 flow rate. (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.
The team have observed that placement of the rubber tubing and u-tube played an important role in the water flow rate. At first we could not even get the water out of the u-tube as the flow rate was too low to exit the u-tube. After thinking, we increased the water level in my pail as we thought that b was way too high for a low water level. At first, we thought that the pump was too weak, however at the end of the experiment, the water level in the pail should also be taken note of as it also affects the flow rate. By doing the experiment and adjusting the measurements by 2cm, we have realised that even a small change in the measurements would affect the results a lot. This is because we could not even get the water to exit the u-tube after giving the measurements a slight change. In this experiment, we have also learnt not to ever give up if the experiment does not show results as we were frustrated at first but we still decided to try different ways to make the apparatus work.
4.Explain how you measure the volume of water accurately for the determination of the flowrate?
I have learnt that measurements and placement of the tubing plays a huge role in water flow rate. In order to measure accurately, I held the measuring cup close to the U-tube to avoid spillage and inaccuracy. Due to lack of appropriate lab equipment for measurement, I used a syringe to measure the access amount of water as my measuring cup only shows markings every 25ml.
5.How is the liquid flow rate of an air-lift pump related to the air flow rate? Explain your reasoning.
Both are related by: When air flow rate increases, liquid flow rate also increases. This is because when the pump is working, it would pump air though the U tube. Hence, when air flow rate increases, there is an increase in pressure at the U tube. This helps “push” the water further up the U shaped tube. Therefore, liquid flow rate increases when air flow rate increases.
6. Do you think pump cavitation can happen in an air-lift pump? Explain.
Cavitation occurs when there is vaporisation of liquid. This happens when the pressure of the liquid at the pump suction is less than the vapor pressure. This would result in vapor bubbles being formed when liquid at pump suction is less than the vapor pressure. Since, there is no liquid flowing at the pump suction, cavitation would not occur.
7.What is the flow regime that is most suitable for lifting water in an air-lift pump? Explain.
The most suitable flow regime is laminar flow. This can be obtained by using Reynold’s number.
We assumed that the density of water is 1000kg/m3and velocity of water to be 0.001kg/m.s. We have also obtained the diameter from measuring the diameter of the u-tube which is 0.012m. We have chosen our flow rate to be 7.43ml/s which is the highest flow rate obtained from this experiment. In order to find velocity, we had to divide the flow rate over the area of the u-tube.
And by using the equation above for Reynold’s number, we have obtained 787.2 which is lesser than 2100, making it laminar.
8.What is one assumption about the water level that has to be made? Explain.
One assumption that has to be made is that the amount of water has to remain constant when water is transferred back to the big jug. This means that water is not lost by evaporation or spillages. This ensures that there is an equal amount of water throughout the experiment.
Photos and videos of experiment
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