Bubbling flow case study

Countereurrent bubble flow with liquid-supported solids, whieh ean be affeeted by downward liquid fluidization of partieles having a density lower than that of the liquid, has been referred to as inverse three-phase fluidization. The mass transfer potential of sueh a eountercurrent operation is worthy of study, especially for cases in whieh dispersion of the gas rather than the liquid is ealled for and the required gas-liquid ratio and throughput ean be effected without flooding. In contrast, the eorresponding eoeurrent mode has reeeived more attention than all other eases and eonstitutes the majority of the literature on three-phase fluidization. 

Zabor et al. (Zl) have described studies of the catalytic hydration of propylene under such conditions (temperature 279°C, pressure 3675 psig) that both liquid and vapor phases are present in the packed catalyst bed. Conversions are reported for cocurrent upflow and cocurrent downflow, it being assumed in that paper that the former mode corresponds to bubble flow and the latter to trickle-flow conditions. Trickle flow resulted in the higher conversions, and conversion was influenced by changes in bed height (for unchanged space velocity), in contrast to the case for bubble-flow operation. The differences are assumed to be effects of mass transfer or liquid distribution. 

A set of experiments on gas-liquid motion in a vertical column has been carried out to study its d3mamical behavior. Fluctuations volume fraction of the fluid were indirectly measured as time series. Similar techniques that previous section were used to study the system. Time-delay coordinates were used to reconstruct the underl3ung attractor. The characterization of such attractor was carried out via Lyapunov exponents, Poincare map and spectral analysis. The d3mamical behavior of gas-liquid bubbling flow was interpreted in terms of the interactions between bubbles. An important difference between this study case and former is that gas-liquid column is controlled in open-loop by manipulating the superficial velocity. The gas-liquid has been traditionally studied in the chaos (turbulence) context [24]. 

As one can see in Table 5.3, from the total amorrrrt of faults injected, around 20 % affected the system arrd cairsed an error in the firral result. When protected by the OCFCM techniqrres, 100% of the faults were detected. In order to confirm these results, we injected another 140,000 faults in the PC (which is the most sensitive area of the microprocessor with respect to control flow errors) of the bubble sort application, due to its low execution time and got 100% fault detection. These results mean that the studied hardening approach was able to fully protect the microprocessor system, by detecting every transient fault injected in the case-study appUcatiorrs. Aside from these results, an average of 1 % faults with no errors per application was detected. 

The design in this case-study prototype device remains an issue for the reversible motion of the liquid. This case-study prototype device could be effectively used for the one shot of liquid in both single-output and multi-output modes on demand. For continuous random switch function, another problem appears if we turn on microchannel X first and desire to next turn on only microchannel Y where X>T. In this continuous switch function, the microchaimel X -f 1) will be also turned on in this case-study prototype device. Anyway, above issues could be resolved via the two-way bubble actuator design [18, 19], which could make the fluid flow backward in the unwanted microchannel. In addition, this microfluidic switch has the potential to be integrated into a wider fluidic network system with stop valves or microflow discretizers which could be used for separation of liquid segments from a continuous source. 

Studies of individual bubbles rising in a two-dimensional gas—Hquid—soHd reactor provide detailed representations of bubble-wake interactions and projections of their impact on performance (Fig. 9). The details of flow, in this case bubble shapes, associated wake stmctures, and resultant bubble rise velocities and wake dynamics are important in characteri2ing reactor performance (26). 

Kister et al. [213] have concluded from examining reported cases of cross-flow channeling related to poor sieve tray column performance that under specific conditions the cross-flow channeling does occur. See Figure 8-142 [213] for diagram of the postulated vapor flow across a tray. It is known to occur for valve trays and bubble cap trays. This condition has not been studied very much in the open literature however, several investigators including myself have observed in industrial practice the... 

The observed ratio / = Lp/Ln, is quite different from that reported for subcooled flow boiling of water in tubes of 17-22 mm inner diameter. Prodanovic et al. (2002) reported that this ratio was typically around 0.8 for experiments at 1.05-3 bar. The situation considered in experiments carried out by Hetsroni et al. (2003) is however different as the bubbles undergo a significant volume change and the flow is unstable. Ory et al. (2000) studied numerically the growth and collapse of a bubble in a narrow tube filled wifh a viscous fluid. The situation considered in that study is also quite different from experiments by Hetsroni et al. (2003) as, in that case, heat was added to the system impulsively, rather than continuously as we do here. 

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