## Transcribed Text

Visual Basic Design
The residence time distribution of a packed column
The Background
The residence time distribution is one of the most important characteristics for continuously
operating chemical engineering equipment such as reactors, mixing tanks distillation and
adsorption columns etc. The residence time distribution tells us what the probability that
a
small portion of liquid needs specific amount of time to pass through the equipment
Luckily there are number of relatively simple methods to measure it. Assume that your
equipment operates steady state. Now you inject very small amount of a "tracer" into the
feed stream AI same time you start measuring the effluent stream see which time your
tracer passes through The result is usually : concentration distribution Over time CIT
For small packed column in one of our labs such measurement has been done The tracer
was salt solution and has been detected using conductance measurements. The primary
result the measurement looks like this
180
160
140
120
80
60
40
20
15
20
t/s
In this particular experiment the conductance Git)is related tothe concentration C(1) via
C(t)=kG(t)
Where the calibration factor k=500M/S (M=moVitre and stands for Siemens).
Classilying equipment according to their residence time behavior is important, but the entire
residence time distribution contains too much information to do that. Therefore one uses
characteristic properties of the distribution such as the mean residence time and the variance.
The mean residence time given by the first moment of the residence time distribution and can
be calculated according
t
(c(n)
The variance the second central moment of the residence time distribution and obtained via
o
Jc(1)dt
Formally the upper limit of the integrations should be infinity but here WA can only integrate the
data we have. (Actually, the students who measured the distribution should have waited bit
longer, because G(1) has not completely decayedito zero when they stopped recording it.)
The Task
Program functions to
1. Calculate the total amount of tracer that was used via
n=v]c(n)dt.
where the volumetric flow rate through the column V =
2. Calculate the mean residence time.
3.
Calculate the variance
You can create many functions as you like. but you are Only allowed three function calls from
the spreadsheet These calls go into the green column titled "value" This means that you are
only allowed edit these three cells; others are protected You are also not allowed to add
anything to the data spreadsheet Or to add new sheets
Your functions also need to be documented This standard practice. However, here we will
alsousei make sure that you are submitting your own work
To dothis prepare document that contains
1) A brief but concise explanation of how each of the three problems has been
implemented.
State andjustify your concept
Brielly explain methodis)used
For the calculation of variance provide the equations that are used in your
code; explain their variables and how the variables are provided in the code
This
could
look
ti)
time
the
i-th
Measurement
from spreadsheet
2) Acopy of your code with line numbers. This should look like:
Public Function WS ideal _gas(Pl, P2, V1)
End Functio
3)
brief but concise explanation of the implementation of the function used to calculate
the variance. Use the folowing table as template.
lines
WS_ideal_gas
function declaration
2
calculation of the surface area of the particle
2-3
calculation of the net fuel usage
4
end of function

These solutions may offer step-by-step problem-solving explanations or good writing examples that include modern styles of formatting and construction
of bibliographies out of text citations and references. Students may use these solutions for personal skill-building and practice.
Unethical use is strictly forbidden.