chapter  66
Thermal Conductivity Measurement
Pages 14

For these reasons, there has been a great interest in the understanding and description of all three heat transfer processes. Among the three, that of thermal conduction is the simplest to describe in principle, since the empirical law of Fourier simply states that the heat transported by conduction per unit area in a particular direction is proportional to the gradient of the temperature in that direction. œe coe¬cient of proportionality in this law is known as the thermal conductivity and denoted here by the symbol λ. Many important materials, whether made of pure chemical components or mixtures, are of uniform composition throughout, and for them the thermal conductivity is a true physical property of the material, depending o£en only on the temperature, pressure, and composition of the sample.