Much has been written about the theoretical background of Flow InjectionudAnalysis (FIA) systems. Until now the prediction of the dispersion in a FIAudsystem was restricted to the use of simple formulae or two-dimensionaludnumerical models. Through recent developments in computer hardware and, atudthe same time, the development of efficient computational fluid dynamicsudsoftware it is possible, with the use of a three dimensional model (based on theudNavier-Stokes equations), to make a 1 to 1 translation between experimentaludsystems and systems based on numerical calculations. A 1 to 1 translationudmeans that only (fundamental) parameters are necessary in the numericaluddescription without the need for fit or match factors. All the known phenomena,udsuch as convection and diffusion, are incorporated in this description. Theudfundamental parameters in this thesis are: the concentrations, the diffusionudcoefficients, the geometry, the flow rates and in case of a reaction, the reactionudconstant, the reaction equation and reaction order.udNext to these macro FIA systems the micro FIA systems are emerging. Theseudsystems have many advantages compared to the traditional macro systems.udTwo examples are: a considerable reduction in analyte consumption and theuddevelopment of portable systems. One disadvantage of the currentudmicrosystems, is the expensive development. It would be very helpful, moneyudwise, if numerical calculations could be used for the development of an optimaludmicrosystem. In this thesis the results of a three dimensional numerical model,udbased on the Navier-Stokes equations, are compared with experimentaludresults. This has been done for channels of different geometries, different flowudrates and a simple reaction.
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