Practical 2
Practical 2
Air-Lift Pump Assignment
Hola peeps! Welcome back to our blog. Well, without further ado let us see what we've been up to on week 6 of the ICPD lesson, shall we?
This week we were assigned to carry out an experiment called the air-lift pump challenge in which we were required to build our own experimental setup with the given items such as PVC tube, u-tube, and an air pump and measure the flow rate of the water displaced. Besides the experiment being carried out we also had to answer some questions related to the assignment and reflect on the learning process throughout the whole experiment to further assess our understanding. Well with that being said here's how the whole process went down.
All members are to jointly work on the discussion are tasked as listed below:
A. Experimental Setup
Experiment Worksheet
Experiment 1
b (fixed) = 10cm
Flowrate is volume of water collected/transferred divided by time taken
Experiment 2
a (fixed) = 2cm
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.
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 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.
Summarise the learning, observations and reflection in about 150 to 200 words.
From the experiment, I learned that creating the experiment is tough as at times during the experiment some mishaps would occur like the air tube sliding out of the U tube, so we had to take other precautions and tape the tube together, using a measuring tape to hold the U tube in place while pumping water and using tape and markers to indicate the level of the air tube location or U tube location in the experiment. Through the experiment, observation on the experiment is on the increasing pump flowrate per tube length increase in X and Y values, from the usage of the pump pumping air to push the water out of the U tube into a breaker to calculate the volume of air through pumped water volume. The experiment has gone decently well with the recording of the height of the water and the setup of the U tube and air tube. However, more can be done in preparation of the instrument to use for the experiment as the equipment for measuring and collecting water is not provided so improvisation of the equipment has to be done.
Explain how you measure the volume of water accurately for the determination of the flow rate?
To measure the volume of water, we pumped the water into a round container with a diameter of 9cm. Once the water has been pumped into the container, we measured the height of the water in the container. Using the formula Volume = Base Area x Height, we are able to find the volume of water in the container.
How is the liquid flowrate of an air-lift pump related to the air flowrate? Explain your reasoning.
The flow rate of air is directly proportional to the flow rate of water. The higher the flow rate of air, the higher the flow rate of water. As air is being pumped, it mixes the water to form a mixture whereby the density is lower than water. This density difference will cause the water to be pumped to a much higher elevation.
Do you think pump cavitation can happen in an air-lift pump? Explain.
Pump cavitation may not happen in an air-lift pump. This is because due to the formula of NPSHA for pumps:
The density of the fluid is usually substituted into the formula in order to create the NPSHA needed in order to determine whether its NPSHA value will be higher or lower than NPSHR, thus to conclude cavitation to be likely or unlikely. However, since the density of air is much lower than water, as density of water is 997 kg/m^3, and that the density of air is 1.225 kg/m^3, its NPSHA will be much higher in an air-lift pump, and thus making cavitation to be unlikely. Therefore, pump cavitation may not happen in an air-lift pump.
What is the flow regime that is most suitable for lifting water in an air-lift pump? Explain.
The flow regime, which includes the pipe diameter, tapering angle of the upriser pipe (rubber/pvc pipe), and the submergence ratio from the surface of the water to the tip of the outer air tube (submergence ratio) are known parameters in order to influence the performance of the pumps. By using these parameters, correct adjustments will ensure optimum flow regime that will be the most suitable for lifting water in an air-lift pump.
The explanation can be found in this graph below:
Figure 1. Airlift pump efficiency versus air mass flow rate for different submergence ratios (researchgate, 2021)
The results show that pumping efficiency of a tapered airlift pump is up to 40% higher than a constant diameter upriser airlift pump (researchgate, 2021). Additionally in our experiment, we found that the optimum level of submergence ratio for the tapered airlift pump is lower than the ordinary airlift pumps.
Because of this, the obtained improvement in pumping efficiency is described by illustrating the flow pattern map of the experimented airlift pump, which is described in addition with the graph above. It shows that the small segment of the tapered upriser (rubber/pvc tube) tends to keep the flow regime in the most optimum region.
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 the liquid flowrate is constant throughout the entire run of the experiment. This means that the flow has to be assumed to be a steady-state, where the mass of fluid within the segment will be constant with time. And accordingly the net mass flow rate of fluid entering the segment must be equal to that of the fluid leaving the segment.
Due to this being the basis of the principle of conservation of mass, continuity equation has to be made, where the mass flow rate entering a cross-section from the water jug that we use to conduct the experiment must be equal to the mass flowrate leaving the cross-section to the 1L container. Additionally, liquids are incompressible, and thus the density remains constant. This can be written as:
Comments
Post a Comment