Heat Transfer by Radiation

Heat transfer by radiation, abbreviated as \(Q_r\) or \(\phi\) (Greek symbol phi), also called heat radiation or radiation heat transfer, is one of four types of heat transfer: conduction, convection, mixing and radiation.  Radiation is the flow of energy through electromagnetic waves such as infrared, light, microwaves, etc.

• See

  Stefan-Boltzmann constant value

 

Heat transfer by radiation formula

\(\large{ Q_r =  \sigma \; A  \left(  T^4 - T_e^4  \right)    }\)

Where:

Units	English	Metric
\(\large{ Q_r }\) = heat radiation	\(\large{\frac{Btu}{hr}}\)	\(\large{ W }\)
\(\large{ A }\) = area of radiating	\(\large{ in^3 }\)	\(\large{ mm^3 }\)
\(\large{ \sigma }\)  (Greek symbol sigma) = Stefan-Boltzmann constant	\(\large{\frac{Btu}{hr-ft^2-R^4}}\)	\(\large{\frac{W}{m^2-K^4}}\)
\(\large{ T }\) = temperature of object emitting	\(\large{ F }\)	\(\large{ K }\)
\(\large{ T_e }\) = temperature of environment	\(\large{ F }\)	\(\large{ K }\)