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in Wiley InterScience (www.interscience.wiley.com).In this work, the flow of immiscible fluids in a PMMA microchannel 300 mm wide and 600 mm deep was investigated experimentally. Dyed de-ionized water and kerosene were selected as the test fluids. Flow patterns were observed by using a CCD camera and were identified by examining the video images. Flow patterns obtained at the T-junction and in the microchannel are presented. Superficial velocities varied between 9.26 Â 10 À4 ; 1.85 m/s for water and 9.26 Â 10 À4 ; 2.78 m/s for kerosene. The formation mechanism of slug, monodispersed droplet and droplet populations at the T-junction was studied. Weber numbers of water and kerosene, We KS and We WS , were used to predict the flow regime transition and the flow patterns map. The experimental data of volume of dispersed phase were successfully correlated as a function of We KS , We WS , and hold-up fraction. Considering the uncertainty associated with experimental quantification of the process, the results are in satisfactory agreement over the wide range of 1.90 Â 10 À3 < We WS < 30.43 and 5.90 Â 10 À6 < We KS < 0.13 with average absolute deviation of only 16.18%.

In this work, the mass transfer characteristics of immiscible fluids in the two kinds of stainless steel T-junction microchannels, the opposing-flow and the cross-flow Tjunction, are investigated experimentally. Water-succinic acid-n-butanol is chosen as a typical example of liquid-liquid two-phase mass transfer process. In our experiments, the mixture velocities of the immiscible liquid-liquid two phases are varied in the range from 0.01 to 2.5 m/s for the 0.4 mm microchannel and from 0.005 to 2.0 m/s for the 0.6 mm microchannel, respectively. The Reynolds numbers of the two-phase mixture vary between 19 and 650. The overall volumetric mass transfer coefficients are determined quantitatively in a single microchannel, and their values are in the ranges of 0.067-17.35 s 21 , which are two or three orders of magnitude higher than those of conventional liquid-liquid contactors. In addition, the effects of the inlet configurations, the fluids inlet locations, the height and the length of the mixing channel, the volumetric flux ratio have been investigated. Empirical correlations to predict the volumetric mass transfer coefficients based on the experimental data are developed.

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Unsteady three-dimensional flow in the mold region of the liquid pool during continuous casting of steel slabs has been computed using realistic geometries starting from the submerged inlet nozzle. Three largeeddy simulations (LES) have been validated with measurements and used to compare results between full-pool and symmetric half-pool domains and between a full-scale water model and actual behavior in a thin-slab steel caster. First, time-dependent turbulent flow in the submerged nozzle is computed. The time-dependent velocities exiting the nozzle ports are then used as inlet conditions for the flow in the liquid pool. Complex time-varying flow structures are observed in the simulation results, in spite of the nominally steady casting conditions. Flow in the mold region is seen to switch between a "doubleroll" recirculation zone and a complex flow pattern with multiple vortices. The computed time-averaged flow pattern agrees well with measurements obtained by hot-wire anemometry and dye injection in fullscale water models. Full-pool simulations show asymmetries between the left and right sides of the flow, especially in the lower recirculation zone. These asymmetries, caused by interactions between two halves of the liquid pool, are not present in the half-pool simulation. This work also quantifies differences between flow in the water model and the corresponding steel caster. The top-surface liquid profile and fluctuations are predicted in both systems and agree favorably with measurements. The flow field in the water model is predicted to differ from that in the steel caster in having higher upward velocities in the lower-mold region and a more uniform top-surface liquid profile. A spectral analysis of the computed velocities shows characteristics similar to previous measurements. The flow results presented here are later used (in Part II of this article) to investigate the transport of inclusion particles.

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