A heat current is a kinetic exchange rate between molecules, relative to the material in which the kinesis occurs. It is defined as, where is heat and is time.
For conduction, heat current is defined by Fourier's law as
- is the amount of heat transferred per unit time and
- is an oriented surface area element
- A is the cross-sectional surface area,
- is the temperature difference between the ends,
- is the distance between the ends.
For thermal radiation, heat current is defined as
where the constant of proportionality is the Stefan–Boltzmann constant, is the radiating surface area, and is temperature.
Heat current can also be thought of as the total phonon distribution multiplied by the energy of one phonon, times the group velocity of the phonons. The phonon distribution of a particular phonon mode is given by the Bose-Einstein factor, which is dependent on temperature and phonon energy.
Famous quotes containing the words current and/or heat:
“Liberty, as it is conceived by current opinion, has nothing inherent about it; it is a sort of gift or trust bestowed on the individual by the state pending good behavior.”
—Mary McCarthy (19121989)
“Coal is a portable climate. It carries the heat of the tropics to Labrador and the polar circle; and it is the means of transporting itself whithersoever it is wanted. Watt and Stephenson whispered in the ear of mankind their secret, that a half-ounce of coal will draw two tons a mile, and coal carries coal, by rail and by boat, to make Canada as warm as Calcutta, and with its comfort brings its industrial power.”
—Ralph Waldo Emerson (18031882)