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THERMAL CONDUCTIVITY OF INSULATING POWDER

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vivek gupta

on 27 October 2014

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Transcript of THERMAL CONDUCTIVITY OF INSULATING POWDER

THERMAL CONDUCTIVITY OF INSULATING POWDER
INTRODUCTION
THEORY:-
OBSERVATION AND CALCULATIONS:-
AIM
To determine thermal conductivity of the insulating powder and understand the heat conduction process involved.
INTRODUCTION
Thermal conductivity is one of the important properties of the materials and its knowledge is required for analyzing heat conduction problems. Physical meaning of thermal conductivity is how quickly heat passes through a given material. Thus the determination of this property is of considerable engineering significance. There are various method of determination of thermal conductivity suitable for finding out thermal conductivity of materials in powdered form.
PROCEDURE
The heater is switched on.
The heat supply can be adjusted to a suitable level.
Temperature readings are noted at frequent till consecutive set of readings are same indicating that steady state has been reached.
The readings of heat input, temperature readings and the geometrical data of the setup are noted in the following table of measurements.
TABULATION
CALCULATIONS:
EXPERIMENTAL SETUP
The setup for the experiment consists of two concentric copper spheres between which the insulating powder, whose thermal conductivity to be determined, is filled. Heater is provided inside the inner sphere for uniform heating of the sphere. Six sets of thermocouples are provided to measure difference across the powder specimen.Provision has been made to measure the heat input.
FORMULAE
VARIATION OF THERMAL CONDUCTIVITY WITH HEAT INPUT
GRAPHS
RESULT
The thermal conductivity of the given insulating powder is determined to be in the range of 0.0774 - 0.096 W/m "C.
By comparing this value with the thermal conductivities of other materials , it is found that the insulating powder is ASBESTOS.
DISCUSSION
The range of the thermal conductivity of the given insulating powder i.e. ASBESTOS is 0.068 to 0.098 which is similar to that found from the experiment.
The thermal conductivity increases when the heat input Q increases.
QUESTIONNAIRE
1. What is thermal conductivity?
2. What is the purpose of heating element?
3. Define outer and inner sphere.
4. What is the need of steady state in
calculating thermal conductivity?
5. What is the type of insulating powder
used ?
6. Define thermal resistance and give its
formula for the setup in above
experiment.
7. What is the mode of heat transfer in
above experiment? Define it.
8. How is the thermal conductivity of
liquid , solid and gases with
temperature.
9. Compare insulating properties of
insulating properties of insulating
materials with other insulators.
10. What are different modes of heat
transfer?

The thermal conductivity of insulating powder increases when the temperature difference between the surface is decreased.
The parameters on which heat transfer depends are:
-
thermal conductivity ,k
:
heat transfer increases when k is increased.
-AREA :
when area increases ,heat transfer increases.
-TEMPERATURE DIFFERENCE:
when the temperature difference is increased ,heat transfer increases.
-LENGTH:
when the length of the slab is increased, heat transfer decreases.