Simple Radiant Heating Method for Determining the Thermal Diffusivity of Cellulosic Materials

Abstract

A simple radiometric method for the determination of the thermal diffusivity of poorly conducting sheet-form materials such as cellulosic kindling fuels is described. The method is a dynamic one based on the ``long time'' solution of the heat-conduction equation for the infinite slab with constant heat-input rate, and utilizes fine-wire thermocouples laminated between sheets of the material (whose diffusivity is required) to measure rates of temperature rise at various depths. The geometry of the system is designed to satisfy as many as possible of the boundary conditions imposed on the mathematical model. The magnitude of errors introduced by violating the other boundary conditions is discussed in connection with the results of measurements on α-cellulose. The value of the thermal diffusivity of α-cellulose containing two percent carbon black and whose density is 0.68 g/cm3 was found to be 1.06±0.06×10−3 cm2/sec.