A new model for the effective thermal conductivity of packed beds of solid spheroids: alumina in helium between 100 and 500°C

An analytical model is given for the thermal conductivity of a bed of solid spheroidal particles in static gas, when the conductivity of the solid is substantially greater than that of the gas. It has two fitting parameters, the width and average radius of the narrow gaps that exist between the irregularly shaped particles and which contribute significantly to the thermal conductivity. Since both parameters are physically measurable, the model holds the potential for calculating the thermal conductivity without any adjustable parameters. Agreement is excellent with measurements on alumina particles in helium at 100–500°C up to 100 kPa pressure.