Effect of Moisture on Ignition Time of Cellulosic Materials

Abstract

The effect of equilibrium moisture content (ranging from 4 to 12.5% moisture, corresponding to 20 to 90% relative humidity) on piloted ignition times of single wall and tri-wall corrugated paperboard samples has been measured over a range of external radiant heat flux (10 to 60 kW/m 2 ) in the Fire Propagation Apparatus (ASTM E-2058). It has been shown for heat fluxes up to 50 kW/m 2 corrugated paperboard samples behave as thermally thin solids and satisfy a simple fundamental equation based on energy required for ignition:

Upward Fire Growth over Thermally Thin Corrugated Paperboard

“…12. It has been shown that for heat fluxes up to 50 kW/m 2 corrugated paperboard behaves as a thermally-thin solid at ignition [17]. During this period, experimentally measured exponential fire growth in terms of chemical heat release rate as a function of time, shown in Fig.…”

“…However, one can assess the role of moisture by using the current model. By changing m w in the model from 0.04 to 0.08 (equilibrium values corresponding to 20 % and 60 % RH) [17], τ g_cal increases about 15 % (see Fig. 9).…”

“…[17] gives the ignition time τ g(thin) including its moisture dependency for a thermally-thin corrugated paperboard as:…”

“…The properties, m   , ig T and 0 c are taken from Ref. [17] and are listed in Table 3 below. One also needs for the model the fractional moisture content, m w , given in Table 4.…”

“…The properties of the various corrugated paperboards used in the study (critical heat flux, flame sootiness in addition to the heats of combustion and gasification) are all obtained from small-scale measurements of ignition, combustion and pyrolysis using the FPA. The objective of the model is to predict the exponential growth time constant including the effects of moisture [17] for the various types of corrugated paperboard.…”