Flow models concentration regimes

This conclusion is supported by iwo other comparisons. If the hump in the retention-time curve, which begins at r=1.2 p. is ignored as an anomaly, the time during which measured tracer concentration exceeded one half of the peak concentration was 0.8S/p, which is slightly less than the value expected. This indicates that (he actual flow regime was closer to plug flow than was predicted The lack of turbulence also is indicated by the value of EUd) achieved al peak concentration this was about 10% higher than was predicted by either flow model (Table 2). 

The smallest size pipeline loop usually considered for measurements intended for industrial scale-up is lin. (2.54 cm) inside diameter [178]. The results are used to determine laminar versus turbulent flow regimes and as input in flow models [178]. Nasr-El-Din [182,183] reviews the methods used to predict pressure drops across emulsions flowing in pipelines, as well as those used to sample and measure oil and solid concentrations in pipelines. An example of an equation for the prediction of water-in-crude oil (North Sea crude oil) emulsion viscosity is given in Equation (6.48). 

It is useful to examine the consequences of a closed ion source on kinetics measurements. We approach this with a simple mathematical model from which it is possible to make quantitative estimates of the distortion of concentration-time curves due to the ion source residence time. The ion source pressure is normally low enough that flow through it is in the Knudsen regime where all collisions are with the walls, backmixing is complete, and the source can be treated as a continuous stirred tank reactor (CSTR). The isothermal mole balance with a first-order reaction occurring in the source can be written as... 

Attempts to use the analytical result of Equation 3 to correlate experimental data have consistently failed (17). Consequently, empirical and semi-empirical models which include various factors to account for evaporation and non-Newtonian behavior have been proposed (17) but these too have not been able to satisfactorily fit the available data. We have considered the coating flow problem with simultaneous solvent evaporation (11). In the regime of interface mass transfer controlled evaporation, i.e. at high solvent concentration, the fluid mechanics problem can be decoupled from the mass transfer problem via an experimental parameter a which measures the changing time-dependent kinematic viscosity due to solvent evaporation. An analytical expression for the film thickness has been obtained (11) ... 

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