Nomenclature 



Symbol Definition Units 



R = Fire spread rate cm. /sec. 



I„ = Reaction intensity—the total intensity available 



from the combustion zone of a spreading fire cal . /cm. 2 -sec . 



1 = Propagating intensity—that portion of the reaction 



P intensity that drives the fire cal . /cm. 2 -sec. 



? = V'r 



e = Effective heating number--the fraction of the bulk 



density that is effectively brought to ignition 



= Ovendry bulk density g./cm. 3 



p = Ovendry particle density g./cm. 3 



Q. = Heat of preignition- -the heat necessary to bring 



a unit ovendry mass uniformly to ignition cal./g. 



2 - Nonuniform heat absorbed per unit volume up to 



ignition cal. /cm. 3 



= Nonuniform heat absorbed per unit ovendry mass for 



the transverse member cal./g. 



Qg = Nonuniform heat absorbed per unit ovendry mass for 



the longitudinal member cal./g. 



V = Unit cell volume cm. 3 

 u 



V A = t 2 £--volume of transverse member of unit cell cm. 3 

 A 



t = Square cross-sectional thickness of unit cell member cm. 



I = Length of unit fuel cell member cm. 



A = t 2 cm. 2 



B = tl cm. 2 



6 = Packing ratio--the ratio of occupied volume to 



the total bulk volume cm. 3 /cm. 3 



C = l--specific heat of water cal./g. -°C. 



Vv" 



C d = C Q + C 1 T--specific heat of dry fuel cal./g.-°C. 



C Q = 0.266 cal./g.-°C. 



C 1 = 0.00116 (cal./g. -°C.)/°C, 



T = Temperature C. 



T = Ambient temperature °C. 



T. = Ignition temperature L - 



f = Fractional fuel moisture content relative to g-/g- 

 its ovendry mass 



H = Heat per unit dry mass absorbed by the transverse 

 member of the unit fuel cell uniformly heated 

 to ignition cal. 



= 540--heat of vaporization of water cal./g. 



^•w 



16 



• U.S. GOVERNMENT PRINTING OFFICE: 1973 784-483 / 7 REGION NO. 8 



