Basics of Thermal Conductivity
What
is Thermal Conductivity?
The measure of a materials ability to conduct heat is
called thermal conductivity. It is usually denoted by
K, Î», k.
Thermal
Conductivity formula
Thermal
conductivity is calculated by using the following formula:
q = k.∇T
Where,
∇T is the temperature gradient
q refers to thermal flux or the heat flux
and
k is the thermal conductivity of the
material.
Factors
affecting Thermal Conductivity
Material  The type of material used in thermal conductivity affects the rate at which the
energy flows between two points. The flow of energy is faster if the
conductivity of the material is high. Some examples of materials with high conductivity
are graphite, copper, diamonds, gold, and silver. The conductivity level of
liquids and gases is low.
Temperature difference  Thermal conductivity may vary
with temperature. The thermal conductivity of a material increases with an
increase in temperature. Also, the flow of energy is increased.
Length  The length of the material affects the rate of
flow of energy. The flow is faster when the length is short. The thermal
conductivity will increase as the length increases but the pace will be slower
than before.
Magnetic field  MaggiRighiLeduc effect is the change of
thermal conductivity of material when placed inside a magnetic field. On
applying magnetic field it develops an orthogonal temperature gradient.
Cross section  The type of crosssection viz, round,
hollowshaped, or C shaped affects the thermal conductivity. It is experienced
that the thermal diffusivity factor value of hollow and Cshaped carbon
fibrereinforced composites twice of roundtype ones.
Thermal
conductivity of common materials in a table form
Sl. no.

Material

Thermal conductivity

1.

Diamond

1000 W/m K

2.

Air (at 0°C)

0.024 W/m K

3.

Steel

50.2 W/m K

4.

Silver

406.0 W/m K

5.

Glass

0.8 W/m K

6.

Gold

314 W/m K

SI
unit of Thermal Conductivity
The expression of thermal conductivity is in terms of the
following  Length, time, temperature, mass.
SI unit is expressed as Wm^{1}K^{1} or
watts per meterKelvin.
Also, expressed as power/(length * temperature).
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