The document details an experiment aimed at determining the thermal conductivity of various metals, explaining key concepts such as heat transfer, temperature gradients, and the importance of minimizing heat loss during measurements. It discusses the use of controlled heat flow in a thermal conductivity apparatus and the challenges of achieving accurate results due to potential errors from convection and radiation. Additionally, it includes tables with specimen characteristics and discussion questions to further analyze the experiment's findings.

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EXPERIMENT NO. 2
((Thermal conductivity))
Aim:
To find the thermal conductivity (k) of a selection of metals.
1. Theory
1.1 Definition of thermal conductivity
Thermal conductivity is heat flow per second per unit area per unit temperature gradient. Heat
conduction / Heat energy is the transferred from the hot end of heat conductor to the cold end
consider a cylindrical conductor as shown in fig. 1, where the temperature at T1 is greater than at
T2, the heat energy flows from the hotter end at temperature T1 to cooler end at temperature T2.
Fig. 1 Cylindrical conductor
Temperature Gradient/the temperature gradient along a material is a temperature change per unit
length, so for the example in fig.1 the temperature gradient is:
(1)
Thermal Conductivity/ to calculate the thermal conductivity of a material the equation must
rearranged to give:
(2)
The heat energy transfer rate (Q/t) is replaced by the power (Wh) for this apparatus and experiment.
This will change the general equation to:
(3)

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Fig. 2 Thermal conductivity measurement apparatus [1]

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2. Controlled heat flow and accuracy
To measure the thermal conductivity of a material, a controlled flow of heat energy must move
along the specimen. The thermal conductivity apparatus has a controllable heater and cooler to
create the heat flow.
For accurate result, the heat loss due to convection and radiation must be minimized, so that all the
heat is transferred by conduction. In a normal environment, much of the heat from the heater
would be lost by convection (see fig. 3), so the heat flow would be difficult to control and measure.
If the average specimen temperature is within a few degrees of the surrounding surface the heat
loss by radiation is very small and can be ignored [2-4]
.
Fig. 3 Heat loss in a normal environment and in the TE19 Low air environment
When the air is removed from around the specimen, there is no gas available for convection to take
place, the heat flow is virtually all due to conduction. However, it is virtually impossible to remove
aal the air or other particles from an environment, this would create a perfect vacuum.
It’s impossible to remove all the air, but the RE19 Vacuum pump creates a very good vacuum, so
that the errors due to convection are very small.

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Table 1 Notation
Table 2 Specimens characteristics

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Table 3 Reading table
2. Discussion questions
a) Why we get different thermal conductivity (k) for the same material?
b) Why we have errors?
c) Discuss the (Wh – K) diagram that you draw it.
d) What do you suggest to get a better reading?
References
1. TecQuipment Ltd, Thermal conductivity measurement apparatus, Model: VDAS TE19.
2. Мохамед Б, Кароли Я, Зеленцов А.А. (2020) Трехмерное моделирование течения газа
во впускной системе автомобиля «формулы студент» Журнал Сибирского
федерального университета, 13(5); pp. 597-610. https://doi.org/10.17516/1999-494X-
0249.
3. Mohamad B., Karoly J., Zelentsov A.A. (2020) Hangtompító akusztikai tervezése hibrid
módszerrel, Multidiszciplináris Tudományok, 9(4), pp. 548-555.
https://doi.org/10.35925/j.multi.2019.4.58.
4. Yunus Cengel, Heat Transfer: A Practical Approach, 2nd
ed., McGraw-Hill Education –
Europe, 1997.
Barhm Abdullah Mohamad
Erbil Polytechnic University
LinkedIn: https://www.linkedin.com/in/barhm-mohamad-900b1b138/
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