Transition from Conductive to Convective Heat Transfer in Fluid-Filled Porous Materials

摘要

The heat transfer mechanism for an infinite, horizontal, fluid-saturated, homogeneous, porous slab is analyzed by assuming the validity of Darcy's law. By perturbing the equilibrium configuration, it is shown that there exists a stability condition for the temperature gradient Beta such that for Beta is greater than 4 pi squared Kappa divided by K sub Alpha h squared (where Kappa is the thermal diffusivity, K is the permeability, h is the thickness through which the thermal gradient is established and Alpha is the bulk thermal expansion coefficient of the fluid), the mechanism of heat transfer changes from conductive to primarily convective. The role of this stability criterion in DDT (deflagration-to-detonation transition) or porous explosives and propellants is discussed.