Inertia-controlled growth

Note that high superheats, large liquid thermal conductivities, low pressures, and low bubble frequencies, all of which are more typical of liquid metals, tend to give bubble dynamics that approach the inertia-controlled case as the bubble growth rates are high. On the other hand, low superheats, low conductivities, high... 

Once the waiting period is over, rapid inertia-controlled bubble growth occurs, the bubble growing in a nearly hemispherical shape as shown in Fig. 15.20c. In this period, a liquid microlayer may be left behind that has a thickness near zero at the original nucleation site and a finite thickness at the edge of the hemispherical bubble. The bubble grows as a result of both evaporation at its upper surface (which is in contact with superheated liquid in the displaced boundary layer) and also by evaporation of this microlayer. 

After the initial rapid growth stage, the growth rate decreases and the bubble growth may become heat-transfer-controlled rather than inertia-controlled this results in a more spherical bubble as shown in Fig. 15.20d. 

In the later stages, bubble growth is controlled more and more by heat transfer to the bubble wall, although for a high-conductivity liquid such as sodium, inertia effects are dominant throughout most of the growth period. 

The basic mechanism of tumble/growth agglomeration is shown in Fig. 6.1. Adhesion of individual particles to each other or to solid surfaces is controlled by the competition between volume and surface related forces (see also Section 5.4). To cause permanent adhesion, certain criteria must be fulfilled. The most important of all is that any system force (e.g. caused by gravity, inertia, drag, etc.) must be smaller than the attraction forces between the adhering partners. According to Fig. 6.2 and Equation 6.1, the ratio between the binding forces Bj(x) and the sum of the active components of all ambient forces F y(x) is a measure for the adhesion tendency T ... 

The subject of diffusion-controlled bubble growth is, of course, a rather small part of the large subject of bubble dynamics, whose scope is too broad to be included in this review. Specifically excluded are cavitation bubbles, whose collapse is inertia rather than diffusion controlled, the formation and detachment of bubbles from orifices, oscillations of bubbles in a pressure field, and the challenging subject of the mechanism of nucleate boiling heat transfer, in which bubble formation and detachment must certainly play a dominant role. 

The formation and subsequent growth of a vapor bubble on a heated wall covered with a liquid is controlled by the forces arising from the excess pressure inside the bubble, the surface tension forces at the liquid-vapor interface and at the contact line formed by the interface at the heater surface, and the inertia forces resulting from the motion of the flow as well as the interface. The resistance to the phase change process at the liquid-vapor interface is quite small in comparison to the... 

The thermal bubble growth could be mainly classified into two modes in macroscale bubble nucleation experiments, as described in an early literature report [15]. The first mode occurs at the initial stage of bubble growth that is hydrody-namically controlled and dominated by liquid inertia. For this first mode, the bubble diameter increases proportionally with heating time. The second mode occurs at the later stage of bubble growth that is dominated by the heat diffusion. 

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