Equation shown in the image is the Stefan-Boltzmann law. “* P*” is the power radiated by the ideal radiator and ‘

**is is the Stefan-Boltzmann constant, which has the value**

*σ*‘^{-8}Wm

^{-2}K

^{-4}

Where ‘P’ is in Watts, emissivity (e) has no units, Area (A) m^{2} and Temperature (T) is in Kelvin. In the thermodynamic analysis the energy density is related from a square per unit time and per unit area. Thus the heat interior surface of an enclosure produces a certain energy density of thermal radiation in the enclosure. We are interested in radiant exchange with surfaces – hence the reason for the expression of radiation from a surface in terms of its temperature.

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sir plz give us more topic for heat transfer