Axial slugging

Intermittent (I) - In this flow pattern the liquid inventory in the pipe is non-uniformly distributed axially. Plugs or slugs of liquid that fill the pipe are separated by gas zones that contain a stratified liquid layer flowing along the bottom of the... 

In vertical flow, axial symmetry exists and flow patterns tend to be somewhat more stable. However, with slug flow in particular, oscillations in the flow can occur as a result of sudden changes in pressure as liquid slugs are discharged from the end of the pipe. 

Yerushalmi and Avidan (1985) suggest that the axial dispersion coefficient of solids in slugging and turbulent flow varies approximately linearly with the bed diameter, similar to Thiel and Potter (1978). The data are shown in Fig. 17 although May s results are probably in the bubbling fluidization regime rather than turbulent flow. 

Chang, S. and Fane, A.G. (2000) Filtration of biomass with axial inter-fibre upward slug flow performance and mechanisms. Journal of Membrane Science, 180, 57-68. 

Consider a fully developed steady-state laminar flow of a constant-property fluid through a circular duct with a constant heat flux condition imposed at the duct wall. Neglect axial conduction and assume that the velocity profile may be approximated by a uniform velocity across the entire flow area (i.e., slug flow). Obtain an expression for the Nusselt number. 

Among other drawbacks of slurry reactors are the high axial dispersion and the low solid fraction that can be held in suspension. Concerning the flow capacity, it should be emphasized that the slurry reactors are less sensitive to gas flow rates, whereas in monolith reactors the gas flow rate is limited by the restrictions of slug flow. 

Guedes de Carvalho et al. [20] studied axial mixing in slug flow. They found the following correlation for the dispersion coefficient ... 

J.R.F. Guedes de Carvalho, S.S.S. Cardoso, and J.A.S. Teixeira, Axial Mixing in Slug Flow. The Use of Injected Air to Reduce Taylor Dispersion in a Flowing Liquid, Trans. Inst. Chem. Eng. 77(A) 28 (1993). 

Figure 12. Effects of the channel curvature on the axial dispersion, (a) The variation of solute concentration within hquid slug as a function of time for various Peclet numbers in straight and serpentine channels, (b) Computational results and theoretical predictions in the absence of molecular diffusion for Ca = 0.01 and 0.005.

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