Flame Emissivity Calculator

Flame Emissivity Calculator

A thin, clean blue flame and a thick, sooty yellow flame radiate very differently even at similar temperatures - the difference is emissivity, which depends on how much soot and radiating gas the flame's light has to pass through.

Formula (Beer-Lambert relation): ε = 1 - e^-kL

Here k is the absorption coefficient (how strongly the flame medium absorbs/emits radiation per meter) and L is the optical path length through the flame.

Example: an absorption coefficient of 0.8 per meter through a 0.3 m flame path gives ε = 1 - e^-0.24 = 0.213 - a moderately radiating flame, well short of a full blackbody (ε=1).

How to Use This Calculator

1. Enter the absorption coefficient in units of 1/m.
2. Enter the optical path length through the flame in meters.

Feed the result directly into the Flame Radiative Heat Loss Calculator to estimate total radiated heat.