Effect of bubbles

Pojman et al. found an unusual mode of propagation when there are large amounts of very small bubbles that can occur when a linear polymer precipitates from its monomer [90]. In studying fronts of methacrylic acid polymerization, they observed convection that periodically occurred under the front at the same time as the front 

Volpert et al. analyzed the effect of the thermal expansion of the monomer on the thermal stabihty and concluded that the reaction front becomes less stable than without thermal expansion [105]. The effective thermal expansion can be increased because of the bubbles, and it can considerably affect the stability conditions. 

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J. Effect of Bubble-Size Distribution and Holdup on Mass- or Heat-Transfer... 

This brief discussion of some of the many effects and interrelations involved in changing only one of the operating variables points up quite clearly the reasons why no exact analysis of the dispersion of gases in a liquid phase has been possible. However, some of the interrelationships can be estimated by using mathematical models for example, the effects of bubble-size distribution, gas holdup, and contact times on the instantaneous and average mass-transfer fluxes have recently been reported elsewhere (G5, G9). 

Gal-Or and Hoelscher (G5) have recently proposed a mathematical model that takes into account interaction between bubbles (or drops) in a swarm as well as the effect of bubble-size distribution. The analysis is presented for unsteady-state mass transfer with and without chemical reaction, and for steady-state diffusion to a family of moving bubbles. 

In this section, a general formulation will be given for the effect of bubble residence-time and bubble-size distributions on simultaneous and thermodynamically coupled heat- and mass-transfer in a multicomponent gas-liquid dispersion consisting of a large number of spherical bubbles. Here one can... 

The effects of bubble formation and of the bursting of bubbles at the surface become clear if filling height H is varied at high gas velocities v (see Fig. 14). At... 

Zahradnik, J. and M. Fialova, The effect of bubbling regime on gas and liquid phase mixing in bubble column reactors. Chemical Engineering Science, 1996. 51(10) p. 2491-2500. 

Effect of bubble density at elevated saturation pressures Gorenflo et al. (1986) interpreted the burnout event as locally coalescing bubbles, and suggested an ap-... 

Barnea, D., 1990, Effect of Bubble Shape on Pressure-Drop Calculations in Vertical Slug Flow, Int. J. Multiphase Flow, 16 79-89. (3)... 

Effect of bubble size on the boiling temperature of pure substances... 

FIG. 24. Optical micrographs of CdTe deposits formed using the thin layer flow cell, with 200 cycles (A) high-quality deposit (B) effect of bubbles in the cavity (C) edge effects and some bubble effects. 

Murhammer and Goochee [93, 94] have confirmed the beneficial effect of Pluronic F-68 addition to insect cell cultures and its protective effect upon bubble damage. The use of PF-68 is today ubiquitous in bioprocess development involving insect cell culture technology, although it may conceivably interfere with VLP formation in some instances. For a more detailed study of the effect of bubble in cell damage mechanisms and the mechanism of protection of PF-68 see the review by Chalmers and the references cited therein [95]. 

Since dissolved-air flotation has been used successfully for oily-waste separation for 20 years, the bulk of the published literature treats the dissolved-air process. No study has been published for either dissolved- or induced-air flotation of oily wastes that considers in detail the effect of bubble or particle size... 

Gas bubbles can also deactivate the electrode surface by forming a physical curtain [173,174], While bubble movement may enhance in situ mass transfer resulting in an increase of the current [175-178], the blocking effect of bubbles can distort measured parameters by introducing a sizable ohmic drop [179-183]. Bubble effects... 

An other important effect of bubbles is to cause the bed to expand. The bed expansion is a consequence of the bubble hold up in the bed and can be calculated from the bubble flow rate and the bubble rise velocity (29 34). For the considions here, a bubble void fraction of 0.3 is assumed, corresponding to an expanded bed height of about lm. From the expanded bed height, bed cross-sectional area, and sorbent feed rate, it can be readily shown that the mean residence time of the limestone in the bed is about 20 hours. 

How would the macro effect of bubbling augment or alter the mixing process ... 

Ahmed, N. and Jameson, G.J. (1985) The effect of bubble size on the rate of flotation of fine particles. Int. J. Miner. Process 14, 195-215. 

Shear Stress. Because mammalian cells lack a cell wall and are larger than bacteria, they are more susceptible to hydrodynamic forces, or shear stress. Several studies have investigated the effects of shear stress on mammalian cells.45 8 Many indicate that the action of the impeller alone does not decrease the viability of suspension-adapted mammalian cells.46,48,49 Some bioprocess engineers in industry have seen a few cell lines that appear to be less robust, and anecdotally might have been damaged by the impeller. However, bubble rupture does cause sufficient hydrodynamic force to kill all the cells attached to the bubble.48 The effects of bubble... 

Similarly, the effects of bubbles in viscoelastic materials were studied by preparing rubber samples containing microvoids. Microvoids were used in order to avoid the effects of bubble resonance and to compare theories in their quasi-static limit. 

These observations, coupled with the effects of bubble texture (1,13-15) and various history dependent phenomena, clearly demonstrate the inadequacy of conventional fractional flow approaches to describe foam flow in porous media. Also, early approaches which treated the foam simply as a fluid of modified viscosity are also inadequate in explaining the above characteristics. To achieve a fuller understanding of such phenomena, a detailed description of the pore level events is required. In what follows, a simple pore level model is utilized to explain some of the above macroscopic features and to identify some of the key pore level mechanisms. 

Sit, S.P. Grace, J.R. Effect of bubble interaction on interphase mass transfer in gas fluidized beds, Chem. Eng. Sci. 1981, 327. 

Figure 4 shows the effect of bubble size on the transient, average carbon concentration. Note that a critical bubble size exists, above which a concentration runaway occurs, i.e., the bed cannot reach a steady state. This is the result of an insufficient rate of oxygen transfer from the bubble phase to the emulsion phase. It can also be seen in the figure that the steady-state average carbon concentration is strongly influenced by the bubble size it increases sharply when the bubble size exceeds a certain value, e.g., 5 cm in this case. 

The effects of bubble size and excess air rate on the transient average bed temperature are illustrated in Figure 5. The effect of bubble size is almost negligible under stable operating conditions, while the effect of excess air has a strong influence on the temperature change. It can be seen in both Figures 4 and 5 that the bed reaches a steady state at about 2000 s after initiation of the operation. This value is very different from the value, 200 s, obtained based on an isothermal dynamic model (10). 

Figure 5. Effect of bubble size and excess air rate on the transient average bed temperature in the type A combustor...

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