Thermal radiation point-source model

The solid-flame model can be used to overcome the inaccuracy of the point-source model. This model assumes that the fire can be represented by a solid body of a simple geometrical shape, and that all thermal radiation is emitted from its surface. To ensure that fire volume is not neglected, the geometries of the fire and target, as well as their relative positions, must be taken into account because a portion of the fire may be obscured as seen from the target. 

Alternative reproach point-source model. Another method of calculating the radiation received by an object relatively distant from the fireball is to use the point-source model. From this approach, the peak thermal input at distance L from the center of the fireball is... 

Two approaches are available for estimating the surface emitted power the point source and solid plume radiation models. The point source is based on the total combustion energy release rate while the solid plume radiation model uses measured thermal fluxes from pool fires of various materials (compiled in TNO, 1979). Both these methods include smoke absorption of radiated energy (that process converts radiation into convection). Typical measured surface emitted fluxes from pool fires arc given by Raj (1977), Mudan (1984), and Considine (1984). LPG and LNG fires radiate up to 250 kW/m (79,000 Btu/hr-ft ). Upper values for other hydrocarbon pool fires lie in the range 110-170 kW/m (35,000-54,000 Btu/hr- ), but smoke obscuration often reduces this to 20-60 kW/m ( 6300-19,000 Btu/hr-ft ). 

Jet fire models based on point source radiation approximations will give poor thermal flux estimates close to the jet, and more mechanistic models should be used. The radiant energy fraction is also a source of error. The models presented here do not apply if wind is present, see Mudan and Croce (1988). 

---