Nucleation and bubble growth

Bubble nucleation model uses a vapour bubble growing on a heater surface with heat diffusion in the vapour phase. This corresponds to post-CHF heat transfer and is an inaccurate model of heat transfer during nucleation and bubble growth. 

During the quasi-steady phase (about 100 ms) the base and exit pressures are nearly constant (Fig. 3). Indeed, the pressure in these experiments is much more constant than in many so-called blowdown experiments, in which nucleation and bubble growth typically occur in the bulk of the liquid (see, e,g.. Winters and Merte [8]). The difference between p ase PexU is the wave amplitude , in this case 0.53 bar. In the steady state the upstream pressure is approximately maintained by the thrust of rapid vaporization. The fact that the exit pressure is greater than the reservoir pressure (namely, 0) indicates that the flow is choked. The instantaneous pressure fluctuates with frequency components between 0 and about 2 kHz the strongest peaks are below 250 Hz. The rms pressure fluctuations are approximately 3% of the mean pressure for both and... 

The experimental studies of Zhang et al. [3] and Li et al. [4], among others, confirm that the conventional nucleation theories of nucleation and bubble growth are valid for microchannel flows as well. The complex interactions due to nucleation, bubble growth and local heat transfer in... 

Fig. 11-19. The drop ejection process in an inkjet printer (a) bubble nucleation (b) bubble growth and drop ejection (c) refill. [From J. H. Bohoiquez, B. P. Canfield, K. J. Courian, F. Drogo, C. A. E. Hall, C. L. Holstun, A. R. Scandalis, and M. E. Shepard, Hewlett-Packard J. 45(1), 9-17 (Feb. 1994). Copyright 1994, Hewlett-Packard Company. Reproduced with permission.]...

Shuai J, Kulenovic R, DroU M (2003) Heat transfer and pressure drop for flow boiling of water in narrow vertical rectangular channels. In Proceedings for 1st International Conference on Micro-channels, Rochester, New York, 24-25 April 2003, ICMM 2003-1084 Staniszewski BE (1959) Nucleate boihng bubble growth and departure MIT DSR Project N7-7673, Technical Report N16... 

Jawurek, H. H., 1969, Simultaneous Determination of Microlayer Geometry and Bubble Growth in Nucleate Boiling, Int. J. Heat Mass Transfer 12 843. (2)... 

Westwater (W4, W5) has written a detailed review of boiling in liquids with emphasis on nucleation at surfaces. Although written in 1956, this is still very useful and it provides a detailed description of the factors affecting nucleation. In a more recent review, Leppert and Pitts (L2) have described the important factors in nucleate boiling and bubble growth, and Bankoff (B2) has reviewed the field of diffusion-controlled bubble growth in nonflowing batch systems. 

The scope of kinetics includes (i) the rates and mechanisms of homogeneous chemical reactions (reactions that occur in one single phase, such as ionic and molecular reactions in aqueous solutions, radioactive decay, many reactions in silicate melts, and cation distribution reactions in minerals), (ii) diffusion (owing to random motion of particles) and convection (both are parts of mass transport diffusion is often referred to as kinetics and convection and other motions are often referred to as dynamics), and (iii) the kinetics of phase transformations and heterogeneous reactions (including nucleation, crystal growth, crystal dissolution, and bubble growth). 

Acoustic intensity has a dramatic influence on the observed rates of sonochemical reactions. Below a threshold value, the amplitude of the sound field is too small to induce nucleation or bubble growth. Above the cavitation threshold, increased intensity of irradiation (from an immersion horn, for example) will increase the effective volume of the zone of liquid which will cavitate, and thus, increase the observed sonochemical rate. 

Staniszewski, B. E., Nucleate Boiling Bubble Growth and Departure. Div. of Sponsored Res., Mass. Inst. Tech., Cambridge, Massachusetts, Tech. Rept. No. 16, 1959. 

Acoustic intensity has a profound effect on the rates of sonochemical reactions. Below a certain value, the amplitude of the wave would be too small to cause nucleation or bubble growth. As the intensity is increased beyond that required for incipient cavitation, the effective size of the liquid zone undergoing cavitation increases and with it the sonochemical rate (Mason, 1990b). This increase is not sustained, however, because amplitudes beyond a certain point lead to excessive cavitation. As a result, there is a reduction in the penetration of the wave into the liquid and therefore of any sonochemical enhancement. 

The electrode reaction may involve the formation of a new phase (e.g. the electrodeposition of metals in plating, refining and winning or bubble formation when the product is a gas) or the transformation of one solid phase to another (e.g. reaction (1.5)). The formation of a new phase is itself a multistep process requiring both nucleation and subsequent growth, and crystal growth may involve both surface diffusion and lattice growth. 

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