(224f) Experimental Studies of Thermal Properties of Packed Powder Beds

Knowing the thermal properties of a given powder/material is important for many industrial applications such as drying and calcination. One such property is the bulk thermal diffusivity, which controls the rate of heat transfer in the powder. Even though the thermal diffusivity is a crucial factor to determine the required time to heat up the powder bed for industrial processes that involve thermal treatment, there is no reliable data of the thermal diffusivity of commonly used powders. We experimentally measured the temperatures inside a packed bed of powders in order to 1) determine the thermal diffusivity of the powders 2) to study the factors, such as density and moisture content, that affect the thermal diffusivity and 3) to relate the powder bed thermal diffusivity (macro scale) to the particle thermal diffusivity (micro scale). Our experiments were performed using a powder filled metal pipe where the temperature of the powder bed could be monitored as it was heated. We collected temperature data using wireless thermocouple transmitters and a receiver; the temperature of the powder bed was recorded from each thermocouple every second with an accuracy of 1ºC. We calculated the thermal diffusivity of the powders based on the measured temperature and Heisler charts. For all the materials we tested, the thermal diffusivity varied from 0.5E-07 to 1.3E-07 (m²/s). In this talk, we will present details of the experimentally measured temperature, factors affecting thermal diffusivity, and comparisons with particle scale heat transfer simulations.