### Relation between defects and crystalline thermal conduction | …

4/7/2019· where U is the thermal energy per unit volume of the material; q is the heat flux (thermal energy passing per unit of time through a unit of area); c is the heat capacity of a unit volume of material. The first of Eq. is the heat energy balance equation, the second is the Fourier thermal conductivity law, the third expresses the relationship between changes in thermal energy and temperature