Dissipation is the result of an
irreversible process that takes place in inhomogeneous
thermodynamic systems. A dissipative process is a process in which energy (internal, bulk flow kinetic, or system potential) is transformed from some initial form to some final form; the capacity of the final form to do mechanical work is less than that of the initial form. For example,
heat transfer is dissipative because it is a transfer of internal energy from a hotter body to a colder one. Following the
second law of thermodynamics, the
entropy varies with temperature (reduces the capacity of the combination of the two bodies to do mechanical work), but never decreases in an isolated system.