RELATIONSHIP BETWEEN MAXIMUM DIAMETERS AND SAUTER MEAN DIAMETERS IN SUBCOOLED FLOW BOILING WITH SEAWATER

A unique bubble foam flow presents in subcooled flow boiling of 3.5 wt% artificial seawater. Depending on the inlet temperatures of seawater, slug bubbles resulting from foam ruptures might prevail during the boiling period. It is of importance to reveal the Sauter mean diameters of bubbles in foam flow under different experimental conditions for seawater. Such characteristic of bubbles including maximum/minimum diameters and Sauter mean diameters is collected and analyzed from shadowgraph measurements by Image J as current datasets covering various inlet temperatures, heat and mass fluxes for both seawater and de-ionized water. Evidence is presented in this paper to describe the relationship between the maximum/minimum diameters and the Sauter mean diameters. Two existing correlations assuming the Sauter mean diameter is proportional to the maximum diameter are adopted in comparisons with current datasets. One relationship correlating the Sauter mean diameter with the shape characteristic including maximum and minimum diameter is also compared with the dataset. Large mean deviations of 57.10-80.27% and 54.06-76.79% for seawater and de-ionized water are found, respectively. It suggests that the poor applicability of these linear correlations. A new linear relationship with a different constant of 0.376 as its slope for seawater is shown at last with the mean deviation of 8.99% only. It provides the possibility to predict the Sauter mean diameters only with known measurements of geometric characteristics of bubbles from footages by high-speed cameras.