Real-time Monitoring of Coaxial Fluid Reaction Rates and Analysis of Influencing Factors
To enable precise control of the cross-linking process in coaxial reactive flows, this study presents an in-situ method for online measurement of the reaction rate and systematically elucidates the governing factors that influence it. The Ca²⁺ -sensitive chromogenic property of murexide is utilized to create a clear color contrast between the sol and gel layers. After elution to reveal the actual boundary of the cross-linked layer, the reaction front is superimposed on the captured flow images, and its grey-scale intensity is extracted pixel-wise. This protocol allows in-line acquisition of the cross-linked thickness at any axial position and, consequently, the calculation of the mean reaction rate. Results demonstrate that the thickness of the cross-linked layer obtained by the proposed on-line protocol deviates by only 1.09 %, fully satisfying engineering accuracy requirements. Both reactant concentrations exert a positive, co-directional influence on layer thickness and mean reaction rate, with calcium chloride concentration offering superior regulation efficacy. When the total flow rate of the coaxial reactive stream is increased while maintaining a constant flow-rate ratio, the cross-linked thickness decreases whereas the mean reaction rate rises. Conversely, extending the co-flow distance enlarges the layer thickness yet reduces the mean reaction rate.
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