The Simplest Distributed Model

Characteristic quantities used in making variables dimensionless must be capable of being held constant  

If a parametric study of the effect of some quantity is to be done, that quantity should appear in the numerator of one and only one of the dimensionless parameters. 

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THE SIMPLEST DISTRIBUTED MODEL Example 1 The Tubular Reactor... 

With regard to the unsteady state behaviour, only the simplest distributed model based on Fickian diffusion with constant effective diffusivities will be considered in this section. However, two important phenomena which are usually neglected in the literature will be included in the unsteady state modelling because of their importance. These are the adsorption mass capacity of the porous catalyst surface and the heat of chemisorption accompanying the steps of the CSD process. 

Several distribution models have been developed to describe a toxicant s movement through the body. These models help estimate the concentration and duration of a toxicant in a living individual. The simplest distribution models treat the body as one compartment. This assumes that the chemical is spread evenly through the body and eliminated at a steady rate proportional to the amount left in the systan. In reality, few toxicants follow a one-compartment model. A two-compartment model is slightly more complex and usually more realistic. In this estimation, the first compartment clears the toxin from the body steadily with time, similarly to the one-compartment model. The toxicant concentration in a second compartment, however, rises as the first declines. This represents the toxicant s movonent fiom one area of the body to a second compartment, for example, from the blood to adipose tissue (body fat). The concentration in the second compartment also dechnes with time, but at a different rate. This concept can be expanded to multicompartment models that consider additional regions of the body. 

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