Bubbles generation

The bubble size in these cells tends to be the smallest (10 to 50 Im) as compared to the dissolved-air and dispersed-air flotation systems. Also, very httle turbulence is created by the bubble formation. Accordingly, this method is attractive for the separation of small particles and fragile floes. To date, electroflotation has been applied to effluent treatment and sludge thickening. However, because of their bubble generation capacity, these units are found to be economically attractive for small installations in the flow-rate range of 10 to 20 mVh. Electroflotation is not expected to be suitable for potable water treatment because of the possible heavy metal contamination that can arise due to the dissolution of the electrodes. 

Grainger-Allen, T. J. N. Bubble generation in froth flotation machines. Trans. IMMVo 79, C15-22. 1970. 

Bubble generators are commercially available which will produce small neutrally buoyant soap bubbles for use in the visualization of the general flow patterns in rooms. The bubbles are about 3 or 4 mm in diameter and are filled with a lielium/air mixture. In practice, it is difficult to make the bubbles truly... 

The first flow pattern zone corresponds to the isolated bubble (IB) regime where the bubble generation rate is much higher than the coalescence rate. It includes both bubbly flow and/or slug flows and is present up to the onset of coalescence process domination. The second zone is the coalescing bubble (CB) regime, which is... 

Fig. 6 shows the FFT spectrum for calculated bed pressure drop fluctuations at various centrifugal accelerations. The excess gas velocity, defined by (Uo-U ,, was set at 0.5 m/s. Here, 1 G means numerical result of particle fluidization behavior in a conventional fluidized bed. In Fig. 6, the power spectrum density function has typical peak in each centrifugal acceleration. However, as centrifugal acceleration increased, typical peak shifted to high frequency region. Therefore, it is considered that periods of bubble generation and eruption are shorter, and bubble velocity is faster at hi er centrifugal acceleration. 

This assumption was not confirmed by Hsu and Graham (1961) or by West-water and Kirby (1963). The latter observed that Dbfb for carbon tetrachloride is approximately 1,200 ft/hr (366 m/hr), which is different from the value of 920 ft/hr (280 m/hr) for liquids that Jakob tested. Westwater and Kirby also found that the product was not constant at high heat fluxes. At higher heat fluxes (such as q" > 0.2qCI), tw is usually small compared with td. If the heat flux is sufficiently high to make tw td, the maximum rate of bubble generation is reached because the vertical distance between successive bubbles is essentially zero. We then have the simple relationship... 

Since (pGFA) is the mass flux of the bubbles generating from the surface, the CHF in a saturated flow becomes... 

In the rest of this development the rate of drop (bubble) generation will be assumed to be zero. This assumption could easily be removed when analyzing systems in which coalescence exists or a reaction generates a gaseous product. 

After funding by the State of California began in the mid-50s, efforts were made to skim fresh water, first with fine capillary tubes and second with bubble generation to transport the (hopefully) water-enriched solution surrounding the bubbles.Both efforts failed. 

FIGURE 1.5 Silent zone in lee of a hedgerow. Wind-tunnel visualization of air movement over a windbreak, such as a hedgerow, with aid of a bubble generator. Wildlife seek such zones for protection from wind, but information flow through air can be reduced there. (From Moen, 1973.)... 

The air-bubble generating and stabilizing process requires a minimum paste consistency. Silica fume particles are smaller than those of Portland cement and addition of silica fume therefore increases the fine fraction of the particles. The higher fraction of smaller particles then increases the surface area causing a greater binding of the water in the mix. This removes the water required for the bubble-generating process. 

The basic mechanism of plasticizing effect on fresh cement mixes is explained by forming a temporarily stable double layer on cement particles. Since the formation of the double layer is also connected with the surface of particles, the increased demand for AEA, WRA and SP, in silica fume concrete and the decreased demand for AEA in the presence of a WRA or SP can be directly correlated to the specific surface increase of silica fume-cement blends and the dispersing action of WRAs and SPs in achieving a mortar consistency that enables the air-bubble-generating and stabilizing process [147, 149]. Concrete producers are now cognizant of the effect of these factors. Field silica fume concrete with a satisfactory, stable air-void system can therefore be produced consistently. 

E-Z Stacker and E-Z Tray are commercially available modular air strippers for the ex situ removal of volatile organic compounds (VOCs) from groundwater. E-Z Stacker consists of 4 or 6 stacking units E-Z Tray units are arranged in pull-out drawers. The multiple sieve tray design of the E-Z Stacker uses forced-draft air bubble generation to provide VOC removal. All information is from the vendor and has not been independently verified. 

Fig 9 (from Ref 17) is a nomogram for the period and max radius of the first bubble generated by a TNT expin in deep water. Use of this nomogram is analogous to that described for Fig 8 The equations upon which the nomogram of Fig 9 is based are ... 

This valve can be used to adjust WJ flow of gas and bubble-generation each cell. 

L = vessel liquid depth, cm Nbt - number of bubbles generated per unit lime, min 1... 

Relation Between Single-Bubble Collision Efficiency and the First Order Rate Constant for Droplet Collection First a parameter which describes the frequency at which a continuous-stirred vessel volume is swept by air bubbles must be found. The total volume swept by rising bubbles per unit time is equal to the volume swept by a single bubble as it rises to the liquid surface ( multiplied by the number of bubbles generated per unit time (A). ... 

V.P. Glotov, P.A. Kolobaev and G.G. Neuimin, Investigation of scattering of sound by bubbles generated by an artificial wind in sea water and the statistical distribution of bubble sizes, Sov. Phys. Acoust. 7 (1962) 341-345. 

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