Gray surface to large surroundings
Thermal radiation exchange
Inputs
User-entered effective surface area facing the stated large surroundings.
User-entered gray-surface emissivity from 0 through 1; this screen does not select it.
Absolute surface temperature in kelvins.
Effective large-surroundings absolute temperature in kelvins.
Results
Net radiation from surface
653.38
Net radiative heat fluxq̇
544.49
W/m²Surface emitted radiation
1,055.4
qnet = εσA(Ts⁴ − Tsur⁴); q''net = εσ(Ts⁴ − Tsur⁴)
A first-pass number, not a code check, certification, or approval. Read the method and its limits below. What this is and is not.
Nearby: Sensible heat · Heat-exchanger ΔTlm · Plane-wall conduction · Convection heat rate
Method
Formula, when it applies, and when it does not
Calculate net radiative exchange for a user-defined gray surface facing large isothermal surroundings.
qnet = εσA(Ts⁴ − Tsur⁴); q''net = εσ(Ts⁴ − Tsur⁴)
When
- Gray diffuse surface
- Large isothermal surroundings
- Absolute temperatures
- User-entered emissivity
Don’t
- This is gray-surface Stefan–Boltzmann exchange to large isothermal surroundings using user-entered emissivity and absolute temperatures. It excludes finite-surface view factors, enclosure geometry, spectral and directional behavior, participating gases/flames, reflections, solar load, convection, conduction, insulation, and transient temperature response.
Incropera & DeWitt, Fundamentals of Heat and Mass Transfer