Heat transfer, dynamic characteristics and disturbance to water of bubbles generated on vertical surfaces featuring extreme wettability patterns

•Effect of patterns on heat transfer, bubble dynamics, and perturbation of water.•Correlations containing the influence factor of patterns wettability and width.•Summary of bubble formation modes on different wettability patterns. Surfaces with mixed wettability patterns are one of the potential ways to improve energy conversion efficiency of industrial equipment. It can significantly change the boiling heat transfer proformance of the surface by affecting the bubble dynamics, as well as the flow field properties. Accordingly, this work simultaneously investigates the thermodynamic, bubble dynamics, and water velocity vector field of the bubbles generated on the designed surfaces, through a combination of thermal parameter measurements, high-speed photography, and particle image velocimetry (PIV). The surfaces are designed in six types, and coated by alternating superhydrophilic materials (contact angle of 9.8°) and superhydrophobic materials (contact angle of 154.8°) at intervals with widths of 5 mm, 10 mm, and 15 mm, respectively. The results showed that the different wettability of the pattern at the bubble generation leads to different bubble formation modes, which in turn affects the heat transfer and the initial dynamics of the bubble. The different width of the pattern affects the bubble floatation and water motion. After comparison, it is found that the bubbles have the best heat transfer proformance when they are generated on a superhydrophilic pattern with a width of 15 mm. However, regardless of pattern wettability and width, the bubble frequency, size, and velocity, as well as the water vorticity and velocity, increase with decreasing supercooling, and first increase and then decrease with increasing heat flux. Based on the experimental results, the correlations of bubble velocity and water velocity are modified by introducing the influence factor of wettability patterns. It is tested that it is not only adaptable to the data of this experiment, but can also be generalized to the data of other works.