Heat Transfer Handbook part 134. The Heat Transfer Handbook provides succinct hard data, formulas, and specifications for the critical aspects of heat transfer, offering a reliable, hands-on resource for solving day-to-day issues across a variety of applications. | 1328 MICROSCALE HEAT TRANSFER scattering mechanism is due to either defect or boundary scattering both of which are independent of temperature. The linear relation between the thermal conductivity and temperature in this regime arises from the linear temperature dependence of the electron heat capacity. At temperatures above the Debye temperature the thermal conductivity is roughly independent of temperature as a result of competing temperature effects. The electron heat capacity is still linearly increasing with temperature eq. but the mean free path is inversely proportional to temperature due to increased electron-lattice cohesions as indiaateb by x . . Lattice Thermal Conductivity Thermal conduction within the crystalline lattice is due primarily to acoustic phonons. The original definition of phonons was based on the amplitude of a particular vibrational mode and that the energy contained within a phonon was finite. In this section phonons are treated as p ticles which is analogous to assuming that the phonon is a localized wave packet. Acoustic phonons generally follow a linear dispersion relation therefore the Debye model will generally be adopted when modeling the thermal transport properties and the group velocity is assumedconstant andequal to the speedof soundwithin the material. Thus all the phonons are assumedto be traveling at a velocity equal to the speedof sound which is independent of temperature. At very low temperatures the phonon heat capacity is proportional to T8 while at temperatures above the Debye temperature the heat capacity is nearly constant. The linetic theory equation for the thermal conductivity of a diffusive system eq. is also very useful for understanding conduction in a phonon system. However for this equation to be applicable the phonons must scatter with each other defects and boundaries. If these interactions did not occur the transport would be more radiative in nature. In some problems of interest in .
