Table 2 . --Calculated maximum heat fluxes associated with 



rate of spread and the fuel descriptors 



Fuel type o X Experimental 



& moisture rate of spread 



content P^Q. R„ 

 f ig E 





Q, 

 "0 



ft 3 



/R 



f D 



f- 1 1 

 L • U. • 



■Ft /h-r 



R t 11 /ft 



^ 2 



111 , 



Pal / rm ^ 



DP 



r r 



— Z • D 



Z . OH 



Y 

 A 



1 n~ 3 



1 u 



7A 1 



9A 



Y 

 A 







PP 



- 4.2 



2.02 



X 



10-3 



61.8 



3.06 



X 



10^ 



2.30 



PP 



- 5.3 



1.96 



X 



10 3 



57.0 



2.90 



X 



10"+ 



2. 18 



PP 

 r r 



c; Q 



1 . / o 



Y 

 A 



1 n" 3 



D 1 . U 



9 QD 



Y 

 A 





7 18 

 Z . 1 o 



PP 

 r r 



- O . D 



± , D D 



Y 

 A 



1 n~ 3 

 1 u 



J J . D 



9 >; A 



Y 

 A 



IV 



1 Q 



PP 

 r r 



— i. H . u 



JL . 04- 



Y 

 A 



1 n~ 3 





9 4(5, 



Z . 



Y 

 A 



1 



1 8c; 



PP 

 r r 



— ZU . o 



1 99 



Y 

 A 



1 n~ 3 



9 1 n 



1 74 



Y 



A 



1 u 



1 1 



vVr 





9 17 



Y 

 A 



1 O" 3 



8 



DO . o 



9 71 

 Z . / i 



Y 

 A 





9 HA 

 Z . U4 



WP 



- 6.7 



1.70 



X 



10-3 



50.4 



2.96 



X 



10^ 



2.23 



WP 



- 7.4 



1.62 



X 



10-3 



42.6 



2.63 



X 



10"^ 



1.98 



WP 



- 10.1 



1.47 



X 



10-3 



36.6 



2.49 



X 



10^ 



1.88 



WP 



- 15.3 



1.32 



X 



10"3 



26.4 



2.00 



X 



10^ 



1.51 



WP 



- 21.6 



1.20 



X 



10-3 



17.4 



1.45 



X 



10"^ 



1.09 



LPP 



- 3.6 



1.24 



X 



10-3 



30.6 



2.47 



X 



10^ 



1.86 



LPP 



- 5.4 



1.14 



X 



10-3 



25.8 



2.26 



X 



10^ 



1.70 



LPP 



- 6.5 



.98 



X 



10"3 



21.6 



2.21 



X 



10^ 



1.66 



LPP 



-8.8 



.93 



X 



10-3 



18.0 



1.94 



X 



10^ 



1.46 



LPP 



- 13.4 



.88 



X 



10-3 



12.0 



1.36 



X 



10^ 



1.02 



LPP 



- 23.2 



.77 



X 



10-3 













Heat flux 

 ^T/A 



PP is ponderosa pine 



WP is western white pine 



LPP is lodgepole pine 



The values for ponderosa and western white pine are in agreement with previous laboratory 

 findings. Fires in lodgepole pine needle beds at 23.2 percent MC would not spread even 

 with repeated ignition of the fuel bed leading edge substantiating the above cutoff 

 value. The porosity of this fuel appears to be the factor responsible but additional 

 work with variations in porosity is needed to substantiate this. 



RADIANT HEAT 



The total heat flux related to fire spread was calculated for each set of test 

 fires. These values are tabulated in table 2. The radiant heat fluxes reported by 

 Thomas and Law (1965) are of the same magnitude where a and/or A were varied. This 

 general agreement indicates radiant heat does contribute to rate of spread, but in the 

 present case the energy is the combined sum of the heat transfer components . The next 

 step was to determine how much heat was being supplied by the flame and how much by 

 the combustion zone. Analysis of all the tests showed a nearly constant combustion 

 zone temperature with no significant correlation to fuel moisture content. 



