MODIFIED ZEHNER-SCHLUNDER MODELS FOR STAGNANT THERMAL-CONDUCTIVITY OF POROUS-MEDIA

Modified Zehner-Schlunder models are proposed for calculations of the stagnant thermal conductivity of two types of porous media with spatially periodic structures. The area-contact model is developed to take into consideration finite area contacts between spheres in a packed-sphere bed. It is shown that results based on the area-contact model are in better agreement with experimental data than those based on the original Zehner-Schlunder model especially at high solid/fluid thermal conductivity ratios. The phase-symmetry model is developed for a sponge-like porous medium where each phase is continuously connected and phase symmetry must be maintained in the expression of the stagnant thermal conductivity. The characteristics of these two models are illustrated.