Bubble concentration

Caustic gouging usually occurs only in areas of high heat flux but may also result when heat transfer rates are low, as in horizontal or inclined WT boiler tubes under circumstances in which the steam-water velocity is particularly low. Here, the relatively small volume of BW surrounding the steam bubbles concentrates very quickly, the alkalinity soars, and caustic corrosion develops. 

Balasubrahmanyam A, Pandit AB (2009) Oscillating bubble concentration and its size distribution using acoustic emission spectra. Ultrason Sonochem 16 105-115... 

An application of ultrasound that is becoming increasingly popular in the food industry is the determination of creaming and sedimentation profiles in emulsions and suspensions (Basaran et al., 1998). Acoustic techniques can also assess nondestructively the texture of aerated food products such as crackers and wafers. Air cells, which are critical to consumer appreciation of baked product quality, are readily probed due to their inherent compressibility (Elmehdi et al., 2003). Kulmyrzaev et al. (2000) developed an ultrasonic reflectance spectrometer to relate ultrasonic reflectance spectra to bubble characteristics of aerated foods. Experiments were carried out using foams with different bubble concentration and the results showed that ultrasonic reflectance spectrometry is sensitive to changes in bubble size and concentration of aerated foods. 

The operation of EF is very simple. This is another important feature for EF. By varying current, it becomes possible to create any gas bubble concentration in the flotation medium to fit the variation of the water flow rate and the suspended substances concentration from time to time. If necessary, a gas medium with very great surface area can be formed easily during EF, thereby increasing the probabilities of bubble-particle collision and adhesion and the formation of tenacious particle-bubble complexes (Mallikarjunan and Venkatachalam 1984). 

Equation (4.258) gives the mean bubble velocity vhich is described through the apparent gas velocity v = w / , whereas the linear bubble concentration is given... 

FIG. 17-15 Bubbling-bed model of Kunii and Levenspiel. d, = effective bubble diameter, = concentration of A in bubble, = concentration of A in cloud, Cas = concentration of A in emulsion, q = volumetric gas flow into or out of bubble, kbc = mass-transfer coefficient between bubble and cloud, and k e = mass-transfer coefficient between cloud and emulsion. From Kunii and Levenr spiel. Fluidization Engineering, Wiley, New York, 1969, and Krieger, Malabar, Fla., 1977.)... 

In bubble columns, gas is dispersed in a continuous liquid phase. Uniform bubble size and bubble concentration characterize the homogeneous regime, particularly in the traverse direction indicating the absence of bulk liquid circulation. In contrast, the heterogeneous regime is characterized by a nonuniform bubble concentration, especially in the traverse direction, because of liquid circulation. 

Once the bubbles leave the electrode surface (when they have a radius equal to the departure radius) they diffuse into the bubble diffusion region. This region has a very high bubble concentration [12] with a typical thickness of a few millimetres. The bubbles can still grow. 

It is apparent that the depth region with highest H platelet concentration becomes the location of highest H2 gas bubble concentration and ultimate cleavage. Thus the Ion-Cut takes place at the peak of the implantation damage profile and not at the region of highest H concentration. 

Another coating-application problem involves the meniscus formed at the point of entry of the fiber into the coating liquid at the free surface. As shown schematically in Figure 5, the air streamlines along the free surface of the moving liquid, and the moving fiber will result in a pressure increase at the tip of the meniscus. If this pressure exceeds the pressure-containment capability of the liquid, an air column forms, collapses, and reforms, and air bubbles are entrained in the liquid. These bubbles concentrate in the liquid in time, and large numbers may pass... 

To model the measured transient foam displacements, equations 2 through 12 are rewritten in standard implicit-pressure, explicit-saturation (IMPES) finite difference form, with upstream weighting of the phase mobilities following standard reservoir simulation practice (10). Iteration of the nonlinear algebraic equations is by Newton s method. The three primitive unknowns are pressure, gas-phase saturation, and bubble density. Four boundary conditions are necessary because the differential mass balances are second order in pressure and first order in saturation and bubble concentration. The outlet pressure and the inlet superficial velocities of gas and liquid are fixed. No foam is injected, so Qh is set to zero in equation... 

Foam consists of gas dispersed in a relatively small amount of liquid Two extremes and a continuum of intermediate stages are possible. An example of one extreme is a freshly poured glass of beer Which besides the carbon dioxide already has a significant amount of liquid present. The foam bubbles have no connection to each other and are ball shaped. Because of its much higher specific weight the liquid drains down between the bubbles wile the gas bubbles concentrate on top and by the time become dry . The two stages are therefore called wet or spherical foam and dry or polyhedral foam, see Fig. 2. 

Beyerlein, S.W., Cossmann, R.K., and Richter, H.J. (1985), Prediction of bubble concentration profiles in vertical turbulent two-phase flow, International Journal of Multiphase Elow, 11(5) 629-641. 

The stresses calculated by Eq. (5.14) exist only in the close proximity of a collapsing bubble. The dispersing effect of cavitation, therefore, depends on the bubble concentration—or more exactly, on the number Neb of collapsing bubbles per unit volume and unit time. This quantity, correspondingly the rate of deagglomeration, increases with rising power input through the flow field or by... 

PDA, PIV and HSVI are non-invasive optical techniques, which apply only for transparent solutions. High concentrations of bubbles hamper the visibility of the measurement volume and attenuate the intensity of light. Because of this, optical techniques can be used to investigate small-sized vessels and at low bubble concentrations. 

Local bubble concentration i.e. the gas hold-up is in relation to the ability of bubbles to coalesce. Therefore, local gas hold-ups are required for the development of the models. Local gas hold-ups were determined at positions A-F with the PIV and capillary techniques. The position A was not accessed with the capillary due to impeller. PIV gas hold-ups were determined from the depth, width and height of PIV pictures. The width and the height of PIV pictures were determined by the optical settings of camera. The depth of illuminated plane in the dispersion was obtained from the calibration experiments with a bubble gel. Sensitivity analysis denoted that local gas hold-up determined from the PIV results is relatively insensitive to the depth of the illuminated... 

The measured and computed volumetric shrinkage of SC-15 epoxy resin modified with 3AZF Glass Bubbles is illustrated in Figure 18.4. Unlike epoxy resin modified with nanoclay, the effect of the glass bubble concentration on epoxy resin shrinkage was fairly monotonic with the maximum filler influence (0.151%) located at 2 wt% filler content. This implies that the 2 wt% concentration produced the optimal... 

For the oil droplets to become attached to the bubbles, the bubbles and droplets must come into intimate contact. This contact is promoted by a highly turbulent region, generally located near the bubble generators. Studies have shown that attachment is enhanced by small gas bubbles, large oil droplets, and high bubble concentration. 

High gas bubble concentration (fraction of the gas-water mixture, i.e., vapor) increases the oil recovery. High gas bubble concentrations cannot be obtained in the presence of small oil droplets. Thus, choking or pumping the produced water in a fashion that would create high shear forces and the formation of small oil droplets should be avoided. Field tests demonstrate that oil removal improves as the... 

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