The thermodynamics of irreversible processes is based on the expression of the entropy source density derived in the previous chapter. From it, phenomenological laws of transport can be presented in a unified way. Heat transport is given by Fourier’s law that leads to a heat equation in which Joule and Thomson effects can be included. It can explain thermal dephasing, heat exchangers and effusivity. Matter transport leads to the Dufour and Soret effects, which imply Fick’s law and the diffusion equation, which can be used to discuss Turing patterns and ultramicroelectrode. Transport of two types of charge carrier leads to the notion of diffusion length, giant magnetoresistance and planar Ettingshausen effect. Transport can be perpendicular to the generalised force, as in the Hall, Righi-Leduc and Nernst effects. The formalism accounts also for thermoelectric effects such as the Seebeck and Peltier effects, with which to analyse thermocouples, a Seebeck loop, adiabatic thermoelectric junctions, the Harman method of determing the ZT coefficient of a thermoelectric material and the principle of a Peltier generator.