Radiative Heat Transfer
Radiative Heat Transfer
Every surface radiates heat, and the rate climbs with the fourth power of absolute temperature — which is why radiation dominates at high temperatures.
The radiated power is Q = ε·σ·A·T⁴. where ε is the emissivity, σ the Stefan–Boltzmann constant, A the area and T the absolute temperature.
Inputs
emissivity := 0.85=0.85
sigma_sb := 5.67e-8 W/(m^2·K^4)=5.67e-08 kg/K^4/s^3
A := 1.5 m^2=1.5 m^2
T := 500 K=500 K
Apply the Stefan–Boltzmann law.
Q := emissivity·sigma_sb·A·T^4=4518.28 W
Results
The fourth-power dependence makes radiation negligible near room temperature but dominant in furnaces and re-entry. Subtract the surroundings’ T⁴ term for the net exchange.
Assumptions & limitations
- Grey, diffuse surface of constant emissivity.
- Absolute (kelvin) temperature.
- Emission only (add surroundings for net).