Bubble Detections and Geometric Measurements Using Four Algorithms: Huang, Li, Otsu, and Yen

The image analysis of two-phase flow pattern during subcooled flow boiling of seawater, raw datasets are analyzed through the following routine: collections of image stacks from videos by high-speed camera, 8-bit treatment, scale setting, threshold by algorithms, watershed treatment, and measurements. For the thresholding process, seventeen (17) algorithms embedded in Image J may be employed for the detections and measurements of research of interests (ROIs). In the present study, four algorithms are selected and employed to current datasets covering the whole experimental conditions of subcooled flow boiling of artificial seawater in an annulus with different heat and mass fluxes at the inlet temperatures of 55℃, 65℃, 75℃, and 85℃. Each dataset of one specific inlet temperature consists of 10 frames from the original video with the time interval of 0.04s. After the thresholding and watershed, ROIs are collected for fitting with ellipses based on the assumption that all bubbles can be described by ellipses. Characteristics of both ROIs (counts, area, Feret’s diameter, etc.) and fitted ellipses (equivalent diameters and orientations) are shown and discussed by mean values of each frame of the dataset. At last, discussions and suggestions of selections in algorithms are given.