Inviscid liquids, bubble formation

Bubble Formation in Inviscid Liquids Neglecting Surface Tension Effects... 

This equation closely resembles the empirical expression of Van Krevelen and Hoftijzer (VI) for the bubble formation in inviscid liquids, provided that the gas density is negligible compared to the liquid density. Their relationship... 

Fig. 11. Comparison of Kumar and Kuloor s model (K18) with the data and model of Davidson and Schuler (D9) for bubble formation in inviscid liquids.

Fig. 15. Comparison of the model (S3) with the data collected for bubble formation in inviscid liquids under constant pressure conditions.

Equation (156) is applicable for both bubble and drop formation. Thus, when term (V) is negligible, it describes bubble formation for all fluids when surface tension is important. On further removal of term (IV), it applies for viscous liquids in the absence of surface tension. If only terms (I) and (II) are retained, the equation applies to the inviscid case without surface tension. 

The formation of bubbles at orifices in a fluidised bed, including measurement of their size, the conditions under which they will coalesce with one another, and their rate of rise in the bed has been investigated. Davidson el alP4) injected air from an orifice into a fluidised bed composed of particles of sand (0.3-0.5 mm) and glass ballotini (0.15 mm) fluidised by air at a velocity just above the minimum required for fluidisation. By varying the depth of the injection point from the free surface, it was shown that the injected bubble rises through the bed with a constant velocity, which is dependent only on the volume of the bubble. In addition, this velocity of rise corresponds with that of a spherical cap bubble in an inviscid liquid of zero surface tension, as determined from the equation of Davies and Taylor ... 

The frequency of gas bubbles which are formed steadily through an orifice in a fluidized bed has been studied by Harrison and Leung (H6). Their results show that the mechanism of chainlike bubble formation is the same as that in an inviscid liquid. If all of the excess gas above the minimum fluidization velocity passes through in the form of gas bubbles, the diameter of a sphere having the same volume as the originated bubble is represented by two equations (in units of cm/sec). Van Krevelen and Hoftijzer (V6) found that... 

Bubble formation in a fluidized bed was found experimentally to be very similar to that in an inviscid liquid. At a very low gas flow rate, the frequency and size of the bubbles formed are primarily governed by a balance between the surface tension of the liquid and the buoyancy force of the bubble. The inertia of the liquid moved by the rising bubbles becomes more improtant than the surface tension at higher gas rates. It is in this... 

Using the analogy of bubble formation in an inviscid liquid, Davidson and Harrison (1963) derived equtions for both the bubble frequency and the bubble size (volume), assuming there is no gas leakage from the bubble to the emulsion phase. 

Davidson JF, Schuler BOG. Bubble formation at an orifice in an inviscid liquid. Trans Inst Chem Eng 38 335-342, 1960. 

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