Time Constant of Water Level

In summary, a group of students conducted an experiment to determine the time constant of a water tank. They observed that the time constant for the tank when the water level is falling is 9 minutes, while it is 11.5 minutes when the water level is rising. The two valves, solenoid and hand-operated, do not have any effect on the time constant. However, the analysis of data showed that the inflow and outflow rates were different, leading to different time constant values. The exact reason for this difference is unclear without further information about the setup of the experiment.
  • #1
getthoboy
5
0
I'm curious:

"A group of students needs to determine the time constant of a water tank. FIrst, the student establish an equilibrium level, with a known flow rate into the tank and both valves (solenoid and hand-operated) fully opened. One of the students reduces the input flow and the group records the change in water level as the level drops. after the level reaches a new equilibrium level, the student closes the hand valve. The group then recods the data as the level rises. analysis of data yields that the time constant for the tank when the level is falling is 9 minutes, while the time constant for the rising level is 11.5 minutes."

Why is that so? why is the time constant value different?
 
Physics news on Phys.org
  • #2
getthoboy said:
I'm curious:

"A group of students needs to determine the time constant of a water tank. FIrst, the student establish an equilibrium level, with a known flow rate into the tank and both valves (solenoid and hand-operated) fully opened. One of the students reduces the input flow and the group records the change in water level as the level drops. after the level reaches a new equilibrium level, the student closes the hand valve. The group then recods the data as the level rises. analysis of data yields that the time constant for the tank when the level is falling is 9 minutes, while the time constant for the rising level is 11.5 minutes."

Why is that so? why is the time constant value different?

Welcome to the PF. The inflow has one rate, and the outflow has another rate. They were combining rates in some cases and not in others...
 
  • #3
yep, they do have different rates. but why is one higher than the other?
 
  • #4
getthoboy said:
yep, they do have different rates. but why is one higher than the other?

Um, because if they're different, one has to be higher than the other?

I guess I'm not understanding the crux of your question. I guess all I can say is that the inflow rate is different from the outflow rate? Sorry if I'm not getting your question.
 
  • #5
well. the point is, the time constant of the rising water level is different than the time constant of the falling water level.
but why is that so? what makes the time constant for the falling process smaller than the other?
 
  • #6
Can somebody help me please?
 
  • #7
Are the two valves (solenoid and hand-operated) on the outlet or inlet for the tank?

Also, do you know what determines the time constant for this process?
 
  • #8
the valves do not have any effect on the value of the time constant. But the time constant could be determine by plotting the record on the excell.
But again, why does the values of the time constant differ? why is one higher than the other?
 
  • #9
Without seeing a figure describing your setup, it's hard for us to tell just what is going on. Are the two valves (solenoid and hand-operated) for the outlet or inlet of the tank, or is one for the outlet and the other is for the inlet? The outlet valve(s) do affect the time constant.
 

1. What is the time constant of water level?

The time constant of water level refers to the amount of time it takes for the water level in a container to reach a steady state after being disturbed or changed. It is a measure of the rate at which the water level changes.

2. How is the time constant of water level calculated?

The time constant can be calculated by dividing the volume of water in the container by the surface area of the opening through which water can enter or exit. This is known as the cross-sectional area and is typically measured in square meters. The resulting unit of time is usually in seconds, but can vary depending on the units used for volume and cross-sectional area.

3. What factors can affect the time constant of water level?

The time constant of water level can be influenced by various factors such as the size and shape of the container, the surface tension of the water, the temperature, and the viscosity of the fluid. The presence of obstacles or obstructions in the container can also affect the time constant.

4. Why is the time constant of water level important?

The time constant of water level is important in understanding and predicting the behavior of liquids in different containers and systems. It can also help in designing and optimizing processes that involve the transfer of fluids or in controlling the water level in a particular system. Additionally, the time constant can provide insights into the properties of the fluid and the container.

5. How can the time constant of water level be measured experimentally?

The time constant of water level can be measured by conducting a simple experiment where the water level in a container is disturbed and the time it takes to reach a steady state is recorded. This process can be repeated multiple times with different volumes of water and cross-sectional areas to obtain an average time constant. Alternatively, it can also be calculated using mathematical equations based on the properties of the fluid and the container.

Similar threads

  • Mechanical Engineering
Replies
16
Views
4K
  • Calculus and Beyond Homework Help
Replies
8
Views
3K
Replies
7
Views
1K
  • Earth Sciences
Replies
10
Views
4K
Replies
3
Views
2K
  • Mechanical Engineering
Replies
31
Views
2K
  • Mechanical Engineering
Replies
3
Views
895
  • DIY Projects
2
Replies
36
Views
7K
  • General Engineering
Replies
4
Views
2K
  • General Engineering
Replies
4
Views
2K
Back
Top