Equation Source for Atmospheric Radiation Formula

[djnbcalgary]

Flareman in the thread798-131662 gives the following equation to predict atmospheric transmissivity for flare radiation:

tau = 0.79 * [(100/R)^(1/16)] * [(100/RH%)^(1/16)]
where R = the distance from the flame center and
RH = relative humidity

I've seen this equation presented elsewhere, but I've been unable to discover the source for this equation. Can any one help me out?

Thanks

 

[ione]

A. Brzustowsky and E.C. Sommer developed an empirical equation for the fraction of heat transmitted as a function of relative humidity.

“Predicting Radiant Heating from flares” Proceeding Division of Refining API 1973 vol. 53 p. 863-895