Research on In Situ Thermophysical Properties Measurement during Heating Processes

Biomass pyrolysis is an important way to produce biofuel. It is a chemical reaction process significantly involving heat, in which the heating rate will affect the yield and composition (or quality) of the generated biofuel. Therefore, the heat transfer inside the biomass pellets is important for determining the rate of temperature rise in the pellets. The accurate knowledge of the thermophysical properties of biomass pellets is required to clarify the process and mechanism of heat transfer in the particles and in the reactor. In this work, based on the transient thermoelectric technology, a continuous in situ thermal characterization method for a dynamic heating process is proposed. Multiple thermophysical properties, including thermal conductivity and volumetric heat capacity for corn leaves, are measured simultaneously within a heating process. In temperatures lower than 100 °C, the volumetric heat capacity slightly increases while the thermal conductivity decreases gradually due to the evaporation of water molecules. When the temperature is higher than 100 °C, the organic components in the corn leaves are cracked and carbonized, leading to the increase in the thermal conductivity and the decrease in the volumetric heat capacity against temperature.