Heat Transfer by Radiation

Written by Jerry Ratzlaff on . Posted in Thermodynamics

Heat transfer by radiation ( \(Q_r\) or \(\phi\) (Greek symbol phi) ) is the flow of energy through electromagnetic waves such as infrared, light, microwaves, etc.

Heat Transfer by Radiation formula

\(\large{ Q_r =   \epsilon \sigma  A   \Delta T ^4     }\)         

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

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


\(\large{ Q_r }\) = heat transfer by radiation

\(\large{ \epsilon }\)   (Greek symbol epsilon) = emissivity of the particular body (a number between 0 and 1)

\(\large{ \sigma }\)   (Greek symbol sigma) = Stefan-Boltzmann constant

\(\large{ A }\) = cross sectional area 

\(\large{ \Delta T }\) = change in absolute temperature  \(\large{ \left(  T_o \;-\; T_e  \right)^4  }\)

\(\large{ T_o }\) = absolute temperature of the object emitting

\(\large{ T_e }\) = absolute temperature of the environment


Tags: Equations for Heat Transfer Equations for Heat