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THERMAL CONDUCTIVITY OF INSULATING POWDER
Transcript of THERMAL CONDUCTIVITY OF INSULATING POWDER
OBSERVATION AND CALCULATIONS:-
To determine thermal conductivity of the insulating powder and understand the heat conduction process involved.
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.
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.
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.
VARIATION OF THERMAL CONDUCTIVITY WITH HEAT INPUT
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.
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.
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
6. Define thermal resistance and give its
formula for the setup in above
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
9. Compare insulating properties of
insulating properties of insulating
materials with other insulators.
10. What are different modes of heat
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.
when area increases ,heat transfer increases.
when the temperature difference is increased ,heat transfer increases.
when the length of the slab is increased, heat transfer decreases.
CRITICAL RADIUS OF INSULATION
C.P. Kothandaraman databook
Heat and Mass transfer laboratory
When the thickness of insulation is increased , the heat transfer is reduced.
VARIATION OF THERMAL CONDUCTIVITY WITH (Ti - To)
RANGE OF THERMAL CONDUCTIVITY OF DIFFERENT POWDERS