# Summary

Heat transfer coefficients characterise the transfer of thermal energy in terms of heat flow and temperature difference between two participating media. This article demonstrates how to calculate the radiative heat transfer coefficient and thermal resistance for gray, diffuse radiative exchange.

# Definitions

: | Area of a radiative surface (m^{2}) | |

: | Radiative heat transfer coefficient (W/m^{2}.K) | |

: | Thermal resistance for radiative heat transfer (W/K) | |

: | Temperature of media participating in radiative exchange (K) | |

: | Emissivity of a surface | |

: | Stephen-Boltzmann constant ( = 5.67 x 10^{-8} W/m^{2}.K^{4}) | |

Subscripts | ||

: | Denotes the radiation emitting surface | |

: | Denotes the radiation absorbing surface |

# Radiative Heat Transfer Coefficient

Radiative exchange between two gray, diffuse surfaces may be characterised by calculating the radiative heat transfer coefficient as shown below:

# Radiative Heat Transfer Thermal Resistance

Using this radiative heat transfer coefficient the thermal resistance to radiative heat transfer may be subsequently calculated using the area of the emitting surface as follows:

This is particularly useful for systems where heat transfer occurs using multiple heat transfer mechanisms (i.e. conductive, convective and radiative) and heat transfer analysis is completed using thermal resistance networks.