Stagnant Effective Thermal Conductivities of Soldered Packed-hed

Abstract

Stagnant effective thermal conductivities of soldered packed-bed (ko0) for sphere packing were measured bythe method which is ordinarily used for metal rod. Values of 15-28kcal/m·hr·°C were obtained for solderedpacked-bed made by soldering iron and brass sphere with pewter.The ko0 of soldered packed-bed has been measured to be independent of the orientation of heat flux, since thedistribution of bridge-parts which connect the spherical packings of soldered packed-bed to each other, wasuniform throughout the whole surface of the sphere.A theoretical estimation of the stagnant effective thermal conductivity was tried as follows.At first, the resistance of theimal conduction was estimated on two spherical packings connected to eachother with solder and then a correction was introduced. In soldered packed-bed heat will be conducted along along zig-zag roundabout way. The ratio of the length of zig-zag path to the straight distance was named effectivepath length coefficient (α). The resistance of thermal condution should be multiplied α-fold of that of thefirst model.Three regular types of sphere packing values of α were calculated, and it was found that a has a simplelinear functional relation with the void fraction of soldered packed-bed.α= 0.85+1.18εThus ko0 may be estimated by the following equation, ko0= (1-ε) 3/αΩkpThe agreement between calculated and obserbed ko0 was very good.