Thermographic Observation and Hydrodynamic Patterns of Inclined Ethanol Droplet Train Impingement on a Non-Uniformly Heated Glass Surface

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Droplet train impingement is a fundamental approach to mimic the complicated interactions between the fluid and the substrate in advanced thermal engineering applications in industry. Differently from previous studies, the main original contribution of this study is to perform an inclined droplet train impingement on a non-uniformly heated surface. Ethanol was used as the liquid for droplet train impingement applications, while glass substrate was selected as the target surface. The inclined flow angle was 63 degrees. Both optical and thermographic observations were performed on the target surface by focusing on the droplet impact area. Three experimental sets were created with the Weber numbers 667.57, 841.90, and 998.01. A surface temperature range was selected between 85.00 °C and 200.00 °C, which was above the boiling point of the ethanol. The maximum spreading length was measured at 0.97 mm at the surface temperature of 82.00 °C for the experiment with the Weber number of 998.01, whilst the minimum spreading length was found at 0.18 mm at the highest surface temperature for the experiment with the Weber number of 667.57. A uniform splashing direction was observed above 170.00 °C for all experiments, which meant that the sign of the transition regime appeared.