Determination of The Thermal Conductivity (Two Slabs Guarded Hot Plate Method)

Aim

To find the thermal conductivity of the specimen by two slab guarded hot plate method.

Apparatus Required:

1. Experimental setup of two slab guarded hot plate method.
2. Stabilized Power supply
3. Stop clock

Apparatus Required:

1. Switch on the heater and set an input voltage (60V) using the Voltage regulator
2. The main heater transfer heat by conduction to the wood disc specimen placed on both sides.
3. The main heater transfer heat by conduction to the wood disc specimen placed on both sides.
4. Observe the reading of thermocouples of T5 & T6 fixed on the water side of wooden disc specimen and tabulate them.
5. Take readings until the system reaches steady state and use the steady state reading for calculation.
6. Calculate the thermal conductivity of the wooden disc specimen by applying Fourier's law of conduction.

Observations:

Formula Used

Applying the Fourier's Law of conduction for a Composite wall structure.

Thermal conductivity (K) = QL     W/mK/2A (T_h-T_c)

T_h= Specimen bottom temperature in (°C)

T_c= Specimen top temperature in(°C)

Q₁= heat input to central heater in watts

L₂= Thickness of specimen in m

A₁= Metering area of specimen in m ²

Central heater input (q) = V * I Watts

Where, X = gap between heater plate = 0.003 m.

Specimen hot side temperature (T_h) = [T₁+T₂/2](°C)

Specimen cold side temperature (T_c) = [T₅+T₆/2](°C)

Thermal conductivity of specimen (K) = q*L /2A (T_h-T_c) in W/ mK

Result:

The thermal conductivity of insulating slab is ............................ W/mK

Viva-Voce Questions

What is effect of temperature on thermal conductivity of gases?

Thermal conductivity of gases increases with increasing temperature

State Fourier law?

Fourier law: the rate of heat conduction through a material depends on geometry of medium, its thickness & material of the medium as well as temperature across the medium.

What is effect of temperature on thermal conductivity of metals?

Thermal conductivity of the metals decreases with increase in temperature.

What are the factors affecting the thermal conductivity?

a.Moisture b. Density of material c. Pressure d. Temperature e. Structure of material

What is thermal conductivity?

Thermal conductivity is the rate of heat transfer through a unit thickness of material per unit area per unit temperature difference

Name the material having highest & least thermal conductivity?

Diamond & Freon-12.

Write down the equation for conduction of heat through a hollow cylinder.

Heat conduction is a mechanism of heat transfer from a region of high temperature to a region of low temperature within a medium [solid, liquid or gases] or different medium in direct physical contact.