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.
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 | \(\large{ F }\) | \(\large{ K }\) |