Thermal Conductivity

Thermal Conductivity

• Rate at which heat is transferred by conduction through a unit cross sectional area of a material when a temperature gradient exists perpendicular to thearea.

• The coefficient of thermal conductivity (K factor), is defined as the quantity of heat that passes passes through a unit cube of the substance in a given unit time when the difference in temperature of the two faces is 10C.

• Mathematically, thermal conductivity is expressed as

                             K = Qt/A(T1-T2)

• Q = amount of heat passing through a cross section, A causing a temperature difference, ∆T ((T1-T2),

t = thickness of the specimen.

• K is the thermal conductivity, typically measured as BTU in / (hr.ft2 . 0F) indicates the materials ability to conduct heat energy.

Guarded Hot plate Apparatus Courtesy: Bayer Material Data Sheet.

• Test method: Guarded hot plate test ASTM 177, ISO 2582

• Test Specimen: two identical specimens having plane surface of such size as to completely cover the heating unit surface

• The thickness should be greater than that for which the apparent thermal resistivity does not change by more than 2% with further increase in thickness.