A heat current is a rate of heat transfer across a specified boundary. Its sign requires a chosen direction; unlike heat flux, it is not a rate per unit area.
A heat-current relaxation time measures the decay of a departure from equilibrium carrying heat. It need not equal the momentum relaxation time or the time between arbitrary scattering events. In an isotropic degenerate-electron estimate, . Small-angle inelastic electron-phonon scattering can remove an excitation energy of order while barely changing the electron's velocity direction, thus relaxing heat more efficiently than charge flow.
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Heat current, also known as thermal current, refers to the rate at which heat energy is transferred from one location to another, typically measured in watts (W). It describes the flow of thermal energy due to a temperature difference between two bodies or regions. Heat current can occur through various mechanisms, including conduction, convection, and radiation: 1. **Conduction**: Heat is transferred through direct contact between materials, where differing temperatures cause heat to flow from the hotter object to the cooler one.