Draining Tank Project
Overview: You will be evaluating the volumetric flow rate out of a draining tank. One tank will
drain with a short piece of tubing, the other with a long piece of tubing attached to the spout.
Is there a difference in the drainage rate? Why or why not?
Pre-lab TopHat question: Guess which container will drain faster. Is it the one with the longer
outlet tubing or the one with the shorter piece of tubing? (there is no right or wrong answer at
this point, but you must guess before doing the experiment and refer back to your initial guess
in the evaluation.)
Experiment description: There are 2 identical tanks filled
with water to the 4 or 5 L mark. The tubing inner
diameter (ID) is 3/16 inch ID. Distances between tank
markings and the outlet of the tubing are shown below.
Both tanks are filled to the 5 L mark. At the start of the
experiment, both valves are opened at the same time.
The time to drain 1.00 L of water is recorded, along with
the actual volume drained. Which tank drains faster?
Instructor gathered measurements: These
measurements were gathered by the instructional team.
Vertical distance between 3L and 5L line on tank: 6.7 cm
Vertical distance between 4L and 5L line on tank: 3.4 cm
Vertical distance from 3L line to end of short tube: 17.5 cm
Time to drain 1.00 L (sec)
Trial 1
Trial 2
Trial 3
Vertical distance from 3L line to end of long tube: 134.5 cm
Each tank was drained of 1.00L of water three times. The data for each tank is shown in the
table below.
sections
Short tube tank
39.28
38.40
39.72
Long tube tank
35.56
35.59
34.76
Analysis overview:
1. Starting from the Engineering Bernoulli equation, simplify the equation for each tank.
You may neglect friction losses for the first pass. 2. Do calculations that support your results of which tank drains more quickly. You will
likely have to make some assumptions. Clearly list all assumptions. Calculate the outlet
velocity and outlet flow rate from each tank. Do these calculations for the point where
there are 5 L in the tank and for when there are 4 L in the tank to obtain a max and min
velocities and flow rates for each tank. Average the flow rate to estimate a time to
drain the tank.
3.
Calculate the time to drain 1L of water analytically. (unsteady state mass balance)
4. Calculate the velocity of the water surface inside the tank as the tank drains from 5L to
4L. What is the ratio of velocity at the surface to velocity out of the drain? Is it
reasonable to assume the surface velocity is zero in comparison to the exit velocity?
5. Compare your calculated flowrate to your measured flowrate. Remember that your
measured flowrate is an average. Do the calculated and measured flowrates show the
same result of which drains faster?
6.
Do the flowrates calculated match theoretically calculated flow rates?
7. Using your measured flowrates, calculate the friction losses occurring in each tank.
8. Friction losses generally are a function of velocity. Do your losses show this?
9. If flow rates do not match, and friction losses in the tubing itself are minimal, where else
could losses happen to slow down flow?
Deliverables
Summary: Description of the experiment, initial expectation (pre-lab), actual results
(which tank drained faster), and summary of analysis that supports the results obtained
(why did this tank drain faster). (~1/2 page)
Calculations:
O
Diagram. Draw a diagram of the experiment including all variables. Show all
necessary known parameters in a table (diameters, heights, etc).
O Knowns and assumptions: Clearly list all knowns and all assumptions used.
O Results and Analysis summary. Show experimental data and theoretical
calculated values in a table for each tank. Make sure to include outlet velocity,
outlet flow rate, and time to drain 1L. For theoretical calculations, also include
the min, max, and average velocity and flow rate for the range studied. For
experimental include the vertical velocity of the water surface in the tank. Show
the friction losses that might account for the differences from theoretical non-
friction calculations.
o Analysis and Calculations. Show clearly labelled calculations for the information
in the results and analysis summary table. These may be handwritten. Make
sure all assumptions are clearly listed.
Conclusion. Describe clearly how the analysis supports your observations.
a. What is the ratio of velocity at the surface to velocity out of the drain? Is it
reasonable to assume the surface velocity is zero in comparison to the exit
velocity?
b. Compare your calculated flowrate to your measured flowrate. Do the calculated
and measured flowrates show the same conclusion of which tank drains faster? C. Do the calculated flowrates match theoretical flowrates? If not, what could be
the reason?
d.
Compare your estimated friction losses for each tank. Friction losses generally
are a function of velocity. Do your losses show this?
e. If friction losses in the tubing itself are minimal, where else could losses happen
to slow down flow?
Learning Community Participation. You are allowed, and encouraged, to discuss and
work with your learning community on this project. However, you are not allowed to
copy someone else's work. Please identify who you worked with on this project. This is
purely for informational purposes and will not affect your grade.
People you worked with on this project
Name
Grading Rubric
/10
Part of your learning community? (yes or
no)
Satisfactory
(70-90 %)
Summary: Description of Parts are missing. It's there but
the experiment, initial
parts may be
expectation, actual
results, and summary of
poorly written.
analysis that supports
the results obtained.
(~1/2 page)
Calculations
Clear diagram
/4
Poor (<70%)
Exemplary
(90-100%)
Clearly and well
written and no
more than 1
page
Clear drawing
with caption
describing the
drawing.
Variables are
clearly labelled. Clear list of known
parameters and data
given
/8
Assumptions clearly listed
_/8
Results summary.
Well formatted table of
calculated results from
theory and experiment
/10
Analysis and calculations.
Clear and accurate
calculations
Total
/20
Conclusion.
Clearly written
conclusion of the
analysis
/20
__/70
includes units, all
known variables
and given data
are included,
Assumptions
used are clearly
stated and are
correct
Easy to read
table, includes
units, includes
table title, all
requested data is
included.
Clear and correct
calculations
Clearly written
conclusion of
the analysis