화학공학소재연구정보센터
Industrial & Engineering Chemistry Research, Vol.46, No.24, 8220-8228, 2007
On the breakage of liquid-liquid dispersions in turbulent pipe flow: Spatial patterns of breakage intensity
The breakage of droplets in turbulent pipe flow is a subject of great technological interest. The purpose of this work is to take advantage of state-of the-art theoretical developments and obtain quantitative predictions enhancing our physical understanding of this problem. From this perspective, the subject of the "exact" solutions to an appropriate mathematical model, being recently an issue in the literature, is clarified. Furthermore, the simplest possible mathematical model of the breakage process is derived that retains the complete process parameter dependencies. To implement the model, an appropriate algebraic approach is proposed for the prediction of the radial profiles of key turbulent flow field parameters. This mathematical model adequately relates the breakage pattern in the pipe with the operating process parameters. The results suggest that droplet breakage occurs almost exclusively in an annular region at the periphery of the pipe. Droplets larger than a certain critical size initially have a tendency to break quite rapidly in that region, whereas turbulent diffusion seems to be comparatively slow and cannot spread the fragments into the bulk. This interplay of breakage and diffusion mechanisms seems to lead to initially nonuniform lateral droplet number concentration profiles with rather strong axial (or equivalent time) dependence, over distances of practical significance for process plants. This work clearly suggests that the often-made assumption of uniform conditions in the pipe cross section. regarding size distribution of the droplets that are undergoing breakage, should be reconsidered.