Nucleation-dominated regime

A homogeneous nucleation model was proposed [20, 21] in which radicals react in the aqueous phase with solubilized monomer to form growing oligomeric species (Fig. 3). These species will form particles when the critical water solubility length is reached (/crit-iner). The consequence is that in cases where homogeneous nucleation is the dominating regime of particle nucleation, the water solubility of the monomer, the initiator concentration, and the water solubility of the initiator become important parameters in the emulsion polymerization process. 

In convective vaporization, the same boiling regimes are encountered, but modified by the net motion of the two-phase fluid past the surface. At low velocities or high heat fluxes, the convection effect is small, and nucleate boiling dominates. At higher velocities, the heat-transfer rate is dominated by the two-phase mixture sweeping across the surface. It is still important to avoid transition and film boiling, but the onset of these phenomena is complicated by many factors. (See [1, 34].)... 

If the liquid in contact with the wall is not sufficiently superheated to sustain bubble nucleation, then heat removal is by convection through the liquid film, with evaporation occurring at the liquid-vapor interface of the vapor core. This is ofl n the dominant mechanism in thermosiphon reboilers, particularly when they operate in the annular flow regime (discussed below). 

Equations (4.29) and (4.30) represent the two extreme situations that have been treated. They should be considered as asymptotes for the physical situations described by regimes I and II. The nucleation term should dominate in the vicinity of... 

Figure 9.16 Schematic of boiling flow regimes (a) nucleate boiling dominant heat transfer and (b) convective boiling dominant heat transfer...

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