Calculate radiative heat exchange using the Stefan-Boltzmann law.
Radiation scales with the fourth power of absolute temperature, so it is negligible at room temperature and dominant at high temperatures. Temperatures must be in kelvin for the fourth-power term to work. Above about 400 °C radiation exceeds convection, which is why furnace and turbine design is radiation-dominated.
Radiation Heat Transfer
Q̇ = ε σ A (T_s⁴ − T_sur⁴), with temperatures in kelvin
Q̇ = ε σ A (T_s⁴ − T_sur⁴), with temperatures in kelvin Radiation scales with the fourth power of absolute temperature, so it is negligible at room temperature and dominant at high temperatures. Temperatures must be in kelvin for the fourth-power term to work.
Above about 400 °C radiation exceeds convection, which is why furnace and turbine design is radiation-dominated.
This calculator takes 4 inputs: Surface emissivity, Surface area, Surface temperature, Surrounding temperature. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.