Radiation Heat Transfer Calculator Calculate radiative heat flux for various scenarios.
Surface Emission
Small in Large Enclosure
Parallel Plates
Single Surface Emissive Power Net Exchange: Small Body (1) in Large Enclosure (2) Surface 2 (Large Enclosure) Net Exchange: Two Large Parallel Plates Results Heat Flux ($q/A$): — W/m²
Switch to Btu/h·ft²
Notes & Formulas Single Surface Emissive Power: Calculates the radiative heat flux emitted by a surface.
Formula: $q/A = \epsilon \sigma T^4$
$q/A$: Radiative Heat Flux $\epsilon$: Emissivity of the surface (dimensionless, 0 to 1) $\sigma$: Stefan-Boltzmann Constant ($5.670374 \times 10^{-8}$ W/m²K⁴ or $0.1714 \times 10^{-8}$ Btu/h·ft²R⁴) $T$: Absolute Temperature of the surface (K or R) Net Exchange (Small Gray Body in Large Gray Enclosure): Calculates the net radiative heat flux from a small gray surface (1) to a large gray surrounding enclosure (2).
Formula: $q_{1,net}/A_1 = \epsilon_1 \sigma (T_1^4 – T_2^4)$
$q_{1,net}/A_1$: Net Radiative Heat Flux from surface 1 $\epsilon_1$: Emissivity of surface 1 $T_1$: Absolute Temperature of surface 1 (K or R) $T_2$: Absolute Temperature of the large surrounding enclosure (K or R) Net Exchange (Two Large Parallel Plates): Calculates the net radiative heat flux between two large, infinite, parallel, diffuse gray surfaces.
Formula: $q_{12}/A = \frac{\sigma(T_1^4 – T_2^4)}{1/\epsilon_1 + 1/\epsilon_2 – 1}$
$q_{12}/A$: Net Radiative Heat Flux between plates $\epsilon_1, \epsilon_2$: Emissivities of plate 1 and plate 2 $T_1, T_2$: Absolute Temperatures of plate 1 and plate 2 (K or R)