Jet flow regimes

Gas jets in fluidized beds were reviewed by Massimilla (1985). A more recent review is by Roach (1993) who also developed models to differentiate three jet flow regimes jetting, bubbling and the transition. However, most of the data were from jets smaller than 25 mm. The discussion here will emphasize primarily large jets, up to 0.4 m in diameter, and operation at high temperatures and high pressures. The gas jets can also carry solids and are referred to as gas-solid two-phase jets in this discussion. 

The schematic of gas-particle jet interaction zone is shown in Fig. 1. The configuration of this zone (milling zone) differs in dependence on a jet flow regime (subsonic a) or supersonic b)). The diameter of an accelerating nozzle equals Dj. Parameters of a mixture at... 

This review paper is restricted to stirred vessels operated in the turbulent-flow regime and exploited for various physical operations and chemical processes. The developments in the field of computational simulations of stirred vessels, however, are not separated from similar developments in the fields of, e.g., turbulent combustion, flames, jets and sprays, tubular reactors, and multiphase reactors and separators. Fortunately, there is a strong degree of synergy and mutual cross-fertilization between these various fields. This review paper focuses on aspects specific to stirred vessels (such as the revolving impeller, the resulting strong spatial variations in turbulence properties, and the macroinstabilities) and on the processes carried out in them. 

The so-called RIM-process (reactive injection molding) is a current realization of the reactive molding process. The heart of the process is the shock mixing of the reactive ingredients, which is achieved by collision of two jets injected at a pressure of 10 - 20 MPa. The reactive mixture is injected into the mold in a laminar flow regime the pressure at this stage does not exceed 0.1- 0.4 MPa.259 The practical development of this method relies on automatic control systems and modem high quality equipment. 

Figure 6.26 [Continued) Tray action closeupe in various flow regimes, (c) spray. Note the existence of gas jets at tray orifices (orifice positions are marked). Dotted horizontal lines indicate positions of minimum and maximum in the vertical dispersion sensitivity profiles (such as the spray profile shown in Fig. 6,286), id) Inclined gas bubbling under influence of a horizontal liquid flow, typical of the emulsion regime, part c from W) V. Pinczewski and C. J. D. Fell, Trans. Inst. Chem. Engrs. (London), 52. p. 294, 1974 part d from F. J. Zuiderweg. P. A. M. Hofhuis. and J. Kuzniar, Chem, Eng, Res, Des,. 62, p, 39.1984, Parts c and d reprinted courtesy of the Institution of Chemical Engineers, UK.)...

Figure 11.10 A disk electrode subjected to a submerged impinging jet a) schematic illustration b) identification of flow regimes.

It should be mentioned that the extremely low gas consumption (<2 slpm) and the laminar flow regime of the plasma jet generated by MPS render this technique particularly sensitive to external perturbations (Borisov et al., 2008). For this reason, it is preferred to apply somewhat higher plasma powers up to 15 kW and to work in the turbulent flow regime of the plasma plume. 

To separate the surface lifetime from the total time interval between subsequent bubbles an approximation of the dead time according to geometric parameters of capillary and bubble volume was derived Fainerman Lylyk (1982) and Fainerman (1990). A substantial improvement for the exact determination of surface lifetime and its calculation was carried out by Fainerman (1992) who defined a critical point in the experimental curve in co-ordinates "pressure-gas flow rate". This point corresponds to a change in the flow regime from individual bubble formation to a gas jet regime. The calculation of the so-called effective age the surface (effective adsorption time) from the bubble surface lifetime was discussed by different authors ... 

The flow regimes established for the environment created by the array of reachng methane-air jets were similar to the published regimes for single nonreacting circular jets, which are defined in the literature as follows [7] ... 

Huang and coworkers [16,44,45] have also studied the wake-stabilized jet flames in crossflow. They identified six flow regimes corresponding to different jet-to-crossflow momentum flux ratios down-wash R < 0.1), crossflow-dominated (0.1 10) modes. Figures 29.7a through 29.7f present the flow patterns on the symmetry plane of the jet and wake regions [45]. In the down-wash flow mode, a small... 

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