Analytical model for the thermal conductivity of a binary bed of packed spheroids in the presence of a static gas, with no adjustable parameters provided contact conductance is negligible (Q1434626)

The present work generalises the earlier work on thermal conductivity of a monobed model.The binary model differs from the other analytical models due to inclusion of the binary nature of the bed by treating the small spheres between the large ones as a homogeneous material. It does not use the averaging over the volume fractions of the two kinds of particles. The model consists of an uncompressed binary bed of small and large spheroids in the presence of a static gas. The authors assume a narrow gas gap of 0.7 times the radius of a small particle due to local irregularities in the packing of bed. The results have been shown to be in agreement with experiments. A significant result is that no additional experiment fitting parameters are required as long as the conductance of the solid is much greater than all other conductances in the model, and the conductance of the direct contact between spheroids is negligible. But it requires accurate measurements of particle roughness.