Specific heat capacity of wildland foliar fuels to 434 °C

Abstract

Specific heat capacity of eleven live foliar fuels from the southeastern United States was measured to 434 °C using differential scanning calorimetry to improve the modeling of prescribed fire behavior. Techniques which allow measurement of the standard heat capacity, excluding the effects of heat of reaction, were refined. Specific heat of leaves increased with temperature until the onset of pyrolysis. Once pyrolysis began, the specific heat became nearly constant. We present a simple model, suitable for incorporation in computer simulations, which captures this functional shape. This model approach could be applied to other foliar fuels if the chemical composition is known. Measurement of standard heat capacity was used to estimate effective heat of reaction given the measurements of total heat flow which included heat of reaction. For all foliar fuels studied, effective heat of reaction was found to be mildly exothermic between 220 and 350 °C.