A correlation for onset of significant void (OSV) in forced convective subcooled flow boiling

The aim of this research was to propose a new correlation for the onset of significant void (OSV) using a verified database encompassing a broad spectrum of experimental conditions. These conditions included variables such as pressure, inlet subcooling, diameter, length, flow channel, heat flux, and mass flux. The database also accounted for the use of six different coolants (R-113, R-114, R-12, R-22, water, and heavy water) and flow in five distinct heated flow channels (round tube, two types of annular tubes, and two types of rectangular channels). The applicable range of the database is as follows: hydraulic diameter (0.00240–0.0240 m), pressure (1.00–158.00 bar), mass flux (27.50–7500.00 kg/m²s), and heat flux (0.006–8.520 MW/m²). Previous studies have largely focused on acquiring the void fraction distribution, with limited attention given to OSV calculations. To address this gap, we established a database that integrated 206 OSV data points calculated using graphical methods from 402 previously published void fraction distribution datasets. This was further supplemented with 246 verified OSV data points obtained from published literature, resulting in a comprehensive database of 452 OSV data points. Utilizing this database, we developed a new OSV correlation that introduces a novel criterion for flow boiling regions, based on Weber number of 10. This number delineates between a 'surface tension dominated flow region' and an 'inertia dominated flow region.' The new correlation outperformed nine other published correlations in terms of OSV prediction, exhibiting a mean error (ME) of 0.25 % and a root mean square error (RMSE) of 27.56 %.