# Relationship between pressure and total volume discussion I need a full paraphrase with different resources. Cover letter: Cover letter: First of all, the

Relationship between pressure and total volume discussion I need a full paraphrase with different resources. Cover letter:
Cover letter:
First of all, the goal of the experiment was about measuring the pressure and the
volume due to the effect of the temperature for CO2, this single component is defined
as a pure component. So, using PVT simulator we were able to use PREOS (PENGROBINSON) equation in order to calculate phase behaviour (book). The pressure
could be read when only the valve is open. In this experiment, the students were asked
to find the relationship between the volume and the pressure by injecting or
withdrawing mercury. The students learnt that the bubble point appears when the
volume of CO2 in the gas phase is 0.002cc, and the dew point (book) appears when
the volume of CO2 in the liquid phase is 0.002 (book).
each student was asked to find the dew and bubble point for the same component
in four different temperatures to illustrate how the temperature effects these points.
The experiment was done four times so it took about 3 hours to collect data in an
excel sheet. Mercury is used to displace fluids it acts as if it were a solid piston when
manipulated by the hand pump, so it does not react with CO2.
Since mercury could be toxic, this is why the university provided the simulator.
The more we inject mercury the more pressure we have inside the cell. The liquid was
displayed as brown and the gas was displayed as yellow. I could recover that the
pressure-volume of CO2 calculated at temperature of 85 F was 946.08psi and 13.712.
after collecting these data in an excel sheet we had to make a line chart that displays
the relationship between the pressure and the total volume in each experiment.
Theory, concepts and objective of the experiment
As the pressure in pure component in the gas phase increased the molecules tend
to get close and convert to liquid (book). Therefore, if the pressure decreased the
molecule will tend to tear apart and the liquid is changed to vapor.
Figure 1 Typical pressure- volume diagram at a constant temperature
In this experiment the students do not need to do liquid circulation since this
experiment is about a single component not a mixture. A temperature change can
occur in a gas as a result of a sudden pressure change over a valve (COMSOL), but this
won’t happen since we are using PVT simulator. Also, since we are using PVT
simulator the tubes won’t have any volume so everything transferred through the
tubing is measured precisely.
Figure 2 Pressure – volume diagram of ethane at different temperature
Also, to define the dew point (the point where the last drop of liquid is
converted to gas) and the bubble point (the point where the first bubble of gas
appears in the liquid) (book).
Experimental Procedure:
The first thing that was done is to open PVT simulator, a programing screen
appeared we wrote:
Copy lab1G1.la1 setup.par
Thelab
Then the simulator started working at a temperature of 75.2° F (Oven) as illustrated in
Figure3.
Figure3 an illustration of PVT simulator
Then we wanted to open the valves 08 and 09, so we could start
injecting/withdrawing mercury and to measure the pressure. To open the valves, press
F2 then choose the valve number. Then we need to start withdrawing mercury from
the visual cell by using the hand pump. To use the hand pump press F5 then enter the
amount to withdraw mercury from the cell, enter the amount with a negative sign to
indicate that you’re withdrawing (positive sign for injecting). Keep withdrawing, so
you could convert all the liquid into gas. The bubble point will appear if the volume in
the gas phase (yellow box) is between 0.001cc and 0.002cc. The pressure of carbon
dioxide could be defined from the box below the valve 14. Collect the data each time
you withdraw mercury in an excel sheet. And the dew point happens when the brown
box is between 0.001cc and 0.002cc. After converting all the liquid phase into gas
phase withdraw more mercury, so the behavior of the gas phase would be collected. In
the excel sheet for a specific temperature make a line graph which basically contains
the sum of the volume of the gas and the liquid phases in the x-axis versus the
pressure in the y-axis. Then after collecting all the required data you will need to exit
the PVT simulator using the escape bottom. And then do the experiment three more
times each time you will change the temperature, the different temperatures will be
given with respect to G letter. So, you will open the program screen and you will only
change the G1 as G with another number. And do the exact same steps three more
times and collect the data in the same way and do four different graphs for each
different temperature. Figure 4 illustrates withdrawing mercury from the volumetric
cell would result as more gas formed. This explains that mercury is incompressible.
Figure 4 Vaporization of a pure substance at a constant temperature
Results and calculations:
The dew and bubble points were a bit tricky to define. However, I defined both
of them for each experiment precisely. So, in order to find the total volume, we’ll need
to sum the volume of the gas and the volume of the liquid after every
injection/withdrawing of mercury.
The critical point for carbon dioxide is 1071 (book). And the calculated critical from
the experiment as show in the graph is approximately 1060.
The percentage error is:

*100 = 1.027%
G13
VI
Vg
10
11
12
13
13.5
13.7
13.71
10.247
8.169
3.322
1.244
0.551
0.101
0.032
0.002
0
0
0
VGH
0
0
0
0
0
0
0.002
8.465
16.543
25.39
30.468
32.161
33.261
33.43
33.503
35.505
37.505
39.505
P
0
-1
-1
-1
-0.5
-0.2
-0.01
-5
-3
-7
-3
-1
-0.6
-0.1
-0.043
-5
-2
-2
VL+Vg
2000
1418.2
1134.7
996.63
958.16
946.64
946.08
946.08
946.08
946.08
946.08
946.08
946.08
946.08
946.08
933.75
920.04
905.39
10
11
12
13
13.5
13.7
13.712
18.712
24.712
28.712
31.712
32.712
33.362
33.462
33.505
35.505
37.505
39.505
G12:
Vl
Vg
10
12
14
13.8
14.1
14.19
14.29
14.39
14.431
13.468
11.54
6.722
1.904
0.94
0.073
0.025
0.006
0.001
0
0
VGH
0
0
0
0
0
0
0
0
0.002
1.956
5.893
15.711
25.529
27.493
29.26
29.358
29.397
29.407
30.408
35.618
0
-2
-2
-0.2
-0.3
-0.9
-0.1
-0.1
-0.043
-1
-2
-5
-5
-1
-0.9
-0.05
-0.02
-0.005
-1
-3
P
VL+Vg
2000
1199.3
1004.9
1013.9
1001
997.68
994.31
991.22
990.01
990.01
990.01
990.01
990.01
990.01
990.01
990.01
990.01
990.01
984.8
933.01
10
12
14
13.8
14.1
14.19
14.29
14.39
14.433
15.424
17.433
22.433
27.433
28.433
29.333
29.383
29.403
29.408
30.408
35.618
G8:
VL
Vg
10
11
12
13
14
14.2
14.21
14.222
9.838
5.455
1.071
0.194
0.107
0.019
0.006
0.002
0
0
VGH
0
0
0
0
0
0
0
0.001
9.385
18.768
28.152
30.029
30.216
30.404
30.432
30.44
31.442
33.442
0
-1
-1
-1
-1
-0.2
-0.01
-0.012
-5
-5
-5
-1
-0.1
-0.1
-0.015
-0.004
-1
-2
P
VL+vG
2000
1452.6
1183.4
1050.5
987.21
979.65
979.31
978.88
978.88
978.88
978.88
978.88
978.88
978.88
978.88
978.88
973.43
960.9
G1:
VI
10
11
12
13
13.317
7.59
3.008
0.145
0.002
0
0
VG
0
0
0
0
0.002
15.729
28.311
36.174
36.565
38.567
39.567
VHG
0
-1
-1
-1
-0.139
-10
-8
-5
-0.251
-2
-1
P
2000
1382.4
1084.2
940.86
914.1
914.1
914.1
914.1
914.1
901.41
894.67
Tot V(X)
10
11
12
13
13.319
23.319
31.319
36.319
36.567
38.567
39.567
10
11
12
13
14
14.2
14.21
14.223
19.223
24.223
29.223
30.223
30.323
30.423
30.438
30.442
31.442
33.442
Temperature of 75.2 degrees
2500
2000
1500
1000
500
0
0
5
10
15
20
25
30
35
40
45
Saturation Evolope
1100
Pressure
1050
1000
950
900
850
0
5
10
15
20
25
Volume
30
35
40
45
Analysis and discussion:
I noticed the more we withdraw mercury the less pressure we have, also I
noticed that between the bubble point and the dew point the pressure remain constant
and after the dew point it would decrease. In my perspective, I believe that the
simulator gives better results since there are no experimental errors. However, errors
could be made through the simulator. The simulator could take less time than the real
experimental, because of changing the temperature. Also, the mercury when vapor
becomes toxic, so it is safer to use the simulator. I assumed before the experiment that
the pressure would decrease while withdrawing mercury and it was correct.
Furthermore, I assumed that the pressure would remain constant between the Dew and
bubble point. As stated in the theory the tubing system has no volume, so all the
volume was transferred. This could be significantly seen while injecting/withdrawing
the same values the pattern would be noticed as precise. Moreover, the procedure
given was very helpful in order to follow up with the experiment as much as possible.
At first the procedure was not very clear to understand, because it seemed like
programing. Then after reading what the experiment about I got the idea of the
experiment. Based on the experiment the pressure tends to decrease. So, this whole
experiment is about to find the dew and bubble points at different temperature. Source
of errors could be made through human error such that sometimes I do not write the
exact volume injected/withdrawn of mercury. Also, once I clicked F4 while injecting
by accident and the valve for servo was closed and it appeared a “BOOM” screen, and
I lost track for some of the data for G1. Also, thermodynamic equilibrium
instantaneous. Another source of error is joule-Thomson effects are neglected
pressure changes take place isothermally, and mercury is incompressible. The last
source of error is the tubing system might have volume.
Conclusion:
The vapor-pressure line is shrinking into a specific point called critical point. And the
pressure between the bubble and dew point is constant.
References:
1- “Multiphysics Cyclopedia.” COMSOL, www.comsol.com/multiphysics/joulethomson-effect.
2- McCain, William D. The Properties of Petroleum Fluids. PennWell Books, 1990.