Porosity in catalyst particles is essential because it enables reactants to reach the active sites and it enables products to leave the catalyst. The engineering of composite-particle catalysts through the tuning of pore-size distribution and connectivity is hampered by the inability to visualize structure and porosity at critical-length scales. Herein, it is shown that the combination of phase...

We study the distributions of channel openings, local fluxes, and velocities in a two-dimensional random medium of non-overlapping disks. We present theoretical arguments supported by numerical data of high precision and find scaling laws as function of the porosity. For the channel openings we observe a crossover to a highly correlated regime at small porosities. The distribution of velocities...

The formation–distribution of condensed water in diffusion medium of proton exchange membrane fuel cells, and its tendency to reduce the local effective mass diffusivity and to influence cell performance, are studied. First the local effective mass diffusivity of a fibrous diffusion medium is determined as a function of the local porosity and local water saturation, using the network model for ...

In this work a glass micromodel which its grains and pores are non-uniform in size, shape and distribution is considered as porous medium. A two-dimensional random network model of micromodel with non-uniform pores has been constructed. The non-uniformity of porous model is achieved by assigning parametric distribution functions to pores throat and pores length, which was measured using ima...

Petrophysical parameters such as porosity, water and oil saturations, formation resistivity factor, etc. describe the storage capability of the porous media or the capacity of rocks to hold fluids. The modified Archie’s equation . / . , also called the saturation equation, is used to determine the water saturation. Archie’s parameters, namely , , and , are sometimes assumed constant to simp...

The radiative properties of interstellar dust are affected not only by the grain size distribution but also porosity. We develop a model for evolution size-dependent porosity and over entire history galaxy evolution. include stellar production, supernova destruction, shattering, coagulation, accretion. Coagulation is {assumed to be} source use one-zone with constant dense gas fraction ($\eta_\m...