Photographic determination of bubble departure diameter in subcooled flow boiling of aqueous calcium sulfate solution

) solutions. The impacts of heat flux, bulk liquid temperature, volumetric flow rate, and salt concentration were methodically investigated utilizing a laboratory-scale flow boiling loop. Bubble growth and departure processes were recorded by high-speed photography and analyzed with digital image processing techniques. The results demonstrate that increasing heat flux and solute concentration lead to larger bubble departure diameters, while higher flow rates tend to suppress bubble growth. The number of bubbles per unit of volume (Population) also increases with heat flux and concentration, but decreases with flow rate. A new correlation regarding heat flux, Reynolds number, Jakob number, and salt concentration has been developed, which predicts bubble departure diameters within ± 10% of the observed values. This study contributes to the understanding of boiling heat transfer performance for saline solutions and has direct implications for the design and operating conditions of heat exchangers exposed to a scaling fluid. The proposed correlation improves predictive capability within the investigated conditions and may be useful for the design and analysis of heat exchangers operating with scaling fluids.