Flash boiling atomization triggered and driven by intensive radiation

For many applications, the demand for a high-quality liquid spray is crucial. Flash boiling atomization is one of the most promising methods to generate such fine sprays with a high degree of droplet size uniformity. Several mechanisms were proposed to implement this method, which harnesses the liquid's thermal energy to disintegrate it into droplets; the atomized liquid is brought to a highly energetic superheated state either by rapid heating of the liquid or by an abrupt pressure drop. In the present work, we propose and theoretically examine a novel method for spray generation which employs the flash boiling mechanism. By subjecting the liquid to intense volumetric heating and inducing significant homogeneous nucleation (i.e., nucleation flux of more than 10¹²1/m³s), the vapor bubbles nucleate, grow, and subsequently break down the liquid into a fine spray. We analyze the bubbles' expansion process and determine their size before bursting as a reasonable indication of the generated droplets' size. Here we consider a mixed regime where both heterogeneous and homogeneous nucleation may occur. Our results suggest that an increase in the heating power leads to a significant decrease in the bubbles' mean diameter, thus contributing to the refinement of the generated droplets. The study evaluates the energetic efficiency of the proposed novel mechanism, exposing a rather complex behavior. The model predicts a maximum efficiency of 0.05% when homogeneous nucleation is dominant, while the efficiency for systems governed by heterogeneous boiling aspires to near-zero values.