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Thermal Conductivity of Air and oil calculated using
experimental values and compared with literature.
Thermodynamics (National University of Sciences and Technology)
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lOMoARcPSD|13584878
Lab Report #
HVAC Lab
Muhammad Shayan
ME-11C
CMS:290317
Table of Contents
1
Objective:............................................................................................................................................2
2
Apparatus:...........................................................................................................................................2
3
Procedure:............................................................................................................................................2
4
Experimental Data:..............................................................................................................................3
5
6
7
4.1
Air:..............................................................................................................................................3
4.2
Oil:...............................................................................................................................................3
Calculations:........................................................................................................................................4
5.1
Air:...............................................................................................................................................4
5.2
Oil:...............................................................................................................................................4
Results:................................................................................................................................................5
6.1
Air:...............................................................................................................................................5
6.2
Oil:...............................................................................................................................................5
6.3
Reason for Error:..........................................................................................................................5
6.4
Graph:..........................................................................................................................................6
Discussions and Conclusion:................................................................................................................6
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lOMoARcPSD|13584878
Lab Report #
HVAC Lab
Muhammad Shayan
ME-11C
CMS:290317
1 Objective:
The objectives of the experiment are:
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To determine the thermal conductivity of oil and air.
To determine the raise in the internal cylinder due to conduction by air and oil.
2 Apparatus:
Following is the apparatus used for the experiment;
Figure 1: TH-3106
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Inner temperature indicator.
Outer temperature indicator.
Heater power indicator.
Main power switch.
Heater power switch.
Heater power regulator.
Cooling water inlet.
Valves.
Inner cylinder temperature sensors.
Specimen inlet hole.
Cooling water outlet.
Specimen outlet hole.
Outer cylinder temperature sensors.
3 Procedure:
Following is the procedure for the experiment;
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Lab Report #
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HVAC Lab
Muhammad Shayan
ME-11C
CMS:290317
Insert the small cylinder inside the cavity formed in the large cylinder and seal it airtight.
Attach three temperature sensors at the designated spots.
Connect the inlet and outlet tubes of the cooling fluid to the coolant reservoir.
Turn on the power of main equipment.
Open the inlet and outlet valves to allow the air flow in the gap between two cylinders and then
close the valves so that air is entrapped in the gap.
Turn on the heater to heat the inner cylinder and wait for the temperature of the inner cylinder and
outer cylinder to stabilize.
Record the voltage, current and inner and outer cylinder temperatures at different heater power
values.
Now repeat the same experiment for oil as conduction medium between inner and outer cylinder.
Let oil flow into the gap between cylinders by pouring it through the inlet valve and let it flow out
of the outlet valve. Keep the oil flowing till the outflow becomes steady, then close the valve.
4 Experimental Data:
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Gap between cylinders = 0.3mm
Inner cylinder diameter = 33.3mm
Inner cylinder length = 120mm
Outer cylinder diameter = 34.1mm
Outer cylinder length = 100mm
4.1 Air:
Input power (W)
19.93
29.88
36.68
50.04
59.82
70.52
Inner Temperature
(oC)
37
44.8
52.4
61.7
69.3
77.6
Outer Temperature
(oC)
19.8
20.5
21.1
21.9
22.5
23.4
Temperature
Difference (oC)
17.2
24.3
31.3
39.8
43.8
54.2
Inner Temperature
(oC)
26.3
30.8
37
42.7
49.5
56.8
Outer Temperature
(oC)
22.7
25.4
29.6
33.5
38.4
43.8
Temperature
Difference (oC)
3.6
5.4
7.4
9.2
11.1
13
4.2 Oil:
Input power (W)
19.96
30.02
40
50.32
60.19
70.22
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Lab Report #
HVAC Lab
Muhammad Shayan
ME-11C
CMS:290317
5 Calculations:
Now, we can find the value of thermal conductivity coefficient for both air and oil by using the
information in the tables above;
We can calculate the value of k by plugging in the values in the above formula;
5.1 Air:
For all the values given in the above table;
Reading
s
1
Thermal conductivity of air
2
0.046
3
0.047
4
0.047
5
0.051
6
0.049
Average
0.0472
(W/mK)
0.043
5.2 Oil:
For all the values given in the above table;
Reading
s
1
Thermal conductivity of Oil
2
0.202
3
0.204
4
0.206
5
0.204
6
0.204
Average
0.2048
(W/mK)
0.209
6 Results:
Now, lets calculate the difference between the actual and experimental values for thermal conductivity
of both oil and air.
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Lab Report #
HVAC Lab
Muhammad Shayan
ME-11C
CMS:290317
6.1 Air:
Actual Thermal Conductivity of Air = 0.026 W/mK
Experimental value of Thermal Conductivity of Air = 0.0472W/mK
%
6.2 Oil:
Actual Thermal Conductivity of Oil = 0.145 W/mK
Experimental value of Thermal Conductivity of Oil = 0.2048W/mK
6.3 Reason for Error:
The reason for such a large value of error in the actual and the experimental value is due to a few
reasons such as the inability to maintain the inner and the outer cylinder temperatures at a constant
value for a certain time. The inaccuracy of the temperature measuring instruments must also be kept
under consideration. Moreover, the experiments need much time for the values to be stable, so provided
time and the number the times the experiment is repeated also affects the error margin.
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Lab Report #
HVAC Lab
Muhammad Shayan
ME-11C
CMS:290317
6.4 Graph:
Power Rating vs Temperature Difference
60
Temperature Difernce
50
40
Air
Linear (Air)
Oil
Linear (Oil)
30
20
10
0
10
20
30
40
50
60
70
80
Power Ratings (W)
7 Discussions and Conclusion:
The results obtained show that oil has greater value of thermal conductivity as compared to that of air,
this means that oil can conduct more heat as compared to that of air provided with same conditions. The
reason for this is the molecular structure of oil, the close spacing of oil molecules as compared to that of
air makes it easier for oil to conduct heat.
The margin of error in the experimental value as compared to the theoretical value can be decreased if
the provide the experiment ample time to stabilize the readings. Repetition of the experiment under
same conditions for a number of times can also reduce the error in the experiment.
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