A. Introduction: Effective Thermal Conductivity

Packed beds are common in nature (e.g., sediments, soils) and find broad engineering application in operations like heat exchange and storage, adsorption, chromatography, drying, biofiltration, heterogeneous catalysis, and many others. As a limiting case, but also for their own sake (e.g., for the calculation of insulations) stagnant packed beds (beds without fluid flow or any movement of the particles) must be considered. Specifically, the effective thermal conductivity λ_bed, of such beds will be discussed in the present section. The very introduction of λ_bed presupposes quasihomogeneous modelling of the porous, dispersed system, by volume-averaging over both phases (Hornung, 1997) and the assumption of negligible temperature differences between the particles and the fluid. As long as this assumption holds, λ_bed may be treated as a material property and finds the same application as the thermal conductivity of any homogeneous body. Limitations will be outlined in Section 201 and Section 202.

B. Primary Parameters and Types of Models

According to the functional dependence

\[\label{eq1} \lambda_{\rm bed} =\lambda_{\rm bed}\left({\lambda_{p},\lambda_{f} ,\psi}\right) \tag{1}\,,\]