Heat Transfer by Radiation

Written by Jerry Ratzlaff on . Posted in Thermodynamics

conduction convection radiantHeat 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 \(\large{ F }\) \(\large{ K }\)

 

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Tags: Equations for Heat Transfer Equations for Temperature