energy flux definition
Heat flux and radiative flux are specific cases of energy flux that involve the rate of transfer of heat and radiation (photons) respectively. Energy flux is a function of time as well as area, and has units of J/m 2 /s or W/m 2. It is sometimes also referred to as flux density. In more technical terms, flux density is defined as the energy travelling over an area perpendicular to the flow of energy divided by time and by area. Four types of energy fluxes for ideal (flat and smooth) surfaces have been identified so far.