Evaluation of effective thermal conductivity from the structure of a packed bed

This paper presents a method to evaluate the effective thermal conductivity from the packing structure of a packed bed of mono-sized spheres in the pr esence of a stagnant fluid. The evaluation is based on two aspects: (i) the heat transfer between particles, which is obtained under some simplified c onditions; and (ii) the connectivity of particles in a packing, which is de termined from the packing structure measured by Finney. Three heat transfer mechanisms or paths are considered in the present modelling, including the conduction through the solid particles and stagnant fluid between non-cont acted particles, the conduction through the solid particles and stagnant fl uid and the conduction through the contact area between contacted particles . The validity of this approach is verified by the good agreement between m easured and calculated results for a packed bed over a wide range of solid- to-fluid thermal conductivity ratio and for packed beds with particles of d ifferent thermal conductivities. (C) 1999 Elsevier Science Ltd. All rights reserved.