Chemical Engineering Lab III during Junior Year at Drexel University

1. Diego Paranhos
Lab Partners: Rose Dillon and Anhtuyet Lam

2. Outline
 Objective
 Theory
 Equipment
 Procedure
 Calculations
 Results & Discussion
 Conclusion
 Recommendations
 Questions

3. Objectives
 Measure thermal conductivity for
various materials and compare to
literature values.
 Analyze the effect of thickness of plexi-
glas on thermal conductivity.

4. Theory
 Transfer of thermal
energy between
neighboring
molecules in a
substance due to a
temperature
gradient

5. Theory
 The Law of Heat
Conduction, also known
as Fourier’s Law was
developed by Joseph
Fourier.
 Always from hot to cold

6. Fourier’s Law
q/A = Heat flux* [W/m2]
k = Material’s thermal conductivity [W/m*K]
dT/dx = Temperature difference [°C]

7. Equipment

8. Materials Used
 6’’ x 6’’ plates
 Ply-wood
 Plexi-glas
 Stainless Steel

9. Procedure
 Part I – Conduction Heat Transfer through Different Materials (same thickness)
 1. Insert the 6’’ x 6’’ stainless steel plate (thickness: 0.249 in.) into the heat sink.
 2. Close the lid and turn fan on.
 3. Start timer for 5 minutes.
 4. Record T1, T2, and q/A from device every 5 minutes for 40 minutes (8 recordings).
 5. Repeat for the plywood (thickness: 0.221’’) and the plexi-glas plate (thickness: 0.217’’)
 Part II – Conduction Heat Transfer through Plexi-glas By Varying Thickness
 3. Insert the 6’’ x 6’’ plexi-glas plate (thickness: 0.106 in.) into the heater slot.
 4. Close the lid and turn fan on.
 5. Start timer for 5 minutes.
 6. Record T1, T2, and q/A from device every 5 minutes for 40 minutes (8 recordings).
 7. Repeat for the plexi-glas plate (thickness: 0.315 in.) and the plexi-glas plate (thickness:
0.217’’)

10. Calculations
q dT
= −k
A dx
q T2 −T1 ∆T
= −k = −k
A x2 − x1 ∆x
q ∆x
k=
A ∆T

11. Results and Discussion
Stainless Steel
Stainless Steel
0.0215
y = 0.2638x
2
R = 0.4322
0.29000
0.28500
k (W/m*K)
0.28000
0.27500
0.27000
0.26500
0 10 20 30 40 50
Time (min)
Metals have a high electrical conductivity, therefore high
heat conductivity because it uses the same molecules
for both processes.

12. Results and Discussion
Ply-wood
Wood is not a very good conductor, low
thermal conductivity

13. Results and Discussion
Plexi-glas
0.0073
Plexi-glas y = 0.1373x
2
R = 0.3905
0.14300
0.14200
k (W/m*K)
0.14100
0.14000
0.13900
0.13800
0.13700
0 10 20 30 40 50
Time (min)
Not as good of a conductor as stainless steel, but
still better than ply-wood.

14. Data and Percent Error
Average Experimental Theoretical Thermal Percent
Material
Thermal Conductivity Conductivity Error
Stainless Steel 0.28 W/m*K 16.4 W/m*K 98.29 %
Plexi-glas 0.14 W/m*K 0.21-0.26 W/m*K 41.52 %
Plywood 0.08 W/m*K 0.1 W/m*K 15.25 %

15. Layer of Air
Data for plexi-glas is not available

16. Results and Discussion
Plexi-glas varying thickness
Plexi-glas Thickness
0.18
0.16
0.14
k (W/m*K)
0.12
0.1 0.106''
0.08
0.06 0.217''
0.04 0.315''
0.02
0
0 10 20 30 40 50
Time (min)
 Warping
 Layer of air
 External convective currents

17. Average Thermal Conductivity
Average Thermal Conductivity
Thickness
(W/m*K)
0.106'' 0.1299
0.217'' 0.1424
0.315'' 0.1063

18. Conclusion
 Thermal conductivity in metals, such as stainless
steel, is higher than in plexi-glas and ply-wood.
 Thermal conductivity is an intrinsic property and
does not change with thickness, although the
data showed otherwise due to a layer of air
present and external convective currents.

19. Recommendations
 Location of apparatus is prone to external
convective currents by other engineers walking
by it.
 Place apparatus in a corner to protect it.
 A layer of air was present in the heat sink
 Tighter seal on plate will minimize air or have some kind
of vacuum seal.

20. Thank you

21. Questions?