Diffusion dimensional homogeneity

The sausages were considered as infinite cylinders and thermal diffusivity was calculated equal to 3.846 x 10" m s". Constant thermal diffusivity and homogeneity of the food were also the simplifying assumptions necessary to develop a model to predict internal temperature profile in chicken pieces fried under pressure [60]. For the chicken pieces a three-dimensional heat transfer was considered and the predicted results were closer to experimental ones obtained at the center of the pieces, than those obtained near the boundaries. Better simulation was also obtained for more regularly shaped pieces. 

Bieniasz LK (2005) A singularity correction procedure for digital simulation of potential-step chronoamperometric transients in one-dimensional homogeneous reaction-diffusion systems. Electrochim Acta 50 3253-3261... 

In reality, the slip velocity may not be neglected (except perhaps in a microgravity environment). A drift flux model has therefore been introduced (Zuber and Findlay, 1965) which is an improvement of the homogeneous model. In the drift flux model for one-dimensional two-phase flow, equations of continuity, momentum, and energy are written for the mixture (in three equations). In addition, another continuity equation for one phase is also written, usually for the gas phase. To allow a slip velocity to take place between the two phases, a drift velocity, uGJ, or a diffusion velocity, uGM (gas velocity relative to the velocity of center of mass), is defined as... 

Rate equation analyses for classical size exclusion chromatography have been based on treating the porous matrix as a homogeneous, spherical medium within which radial diffusion of the macromolecular solute takes place (e.g. (28,30,31)) or If mobile phase lateral dispersion Is considered Important, a two dimensional channel has been used as a model for the bed (32). In either case, however, no treatment of the effects to be expected with charged Brownian solute particles has been presented. As a... 

A radioactive component is consumed by its decay (homogeneous reaction). For example, one-dimensional diffusion of in zircon along the crystallographic axis c or along any direction in the a-b plane can be described by... 

Generalized local Darcy s model of Teorell s oscillations (PDEs) [12]. In this section we formulate and study a local analogue of Teorell s model discussed previously. The main difference between the model to be discussed and the original one is the replacement of the ad hoc resistance relaxation equation (6.1.5) or (6.2.5) by a set of one-dimensional Nernst-Planck equations for locally electro-neutral convective electro-diffusion of ions across the filter (membrane). This filter is viewed as a homogenized aqueous porous medium, lacking any fixed charge and characterized... 

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