Droplet Impact on a Superheated Concave Surface Having a Curvature Ratio of Unity

In the past, attention has been focused on symmetric superheated surfaces, such as spherical and flat geometries. However, more research needs to be done on how droplet dynamics affect asymmetric curvatures. The focus of the current study is on the impingement of water droplets on asymmetric surfaces, such as cylindrical concave heated surfaces with drop-sized curvatures. Concave surfaces main-trained in the extremely high-temperature range of 250–450 °C are impinged with water droplets. A high-speed imaging technique is utilized to follow a droplet, while the Weber number is varied between 8 and 50. The experiment showed that the droplet shape and spreading characteristics on the aforementioned concave surface are entirely different from those on flat surfaces due to non-uniform momentum distribution. Furthermore, it is demonstrated that impact Weber number and enhanced superheat have an effect on the maximum spread factor and resident time. Since gravity opposes the momentum spreading in concave geometry, it is obvious that around 56% less contact time occurs when compared to flat surfaces. In addition, conversion of enthalpy into vapour pressure contributes to the reduction in contact time.