Droplet train impingement on the heated surface

• Main Author: Tan, Eileen
• Other Authors: Fei Duan
• Format: Final Year Project
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/67740
• Institution: Nanyang Technological University

Liquid droplet interactions have been the topic of interests of many research papers over the years. This is attributed to the complexity and its versatile use in many engineering applications. However, amongst the studies of droplet impingement, few studies have been done on droplet train impinging on a heated surface. Thus, the present experimental study investigates the characteristics of the transitioning wetted area diameter and splashing rebound angle due to a droplet train impinging perpendicularly on a solid surface on three varying surface roughness (0.136 µm, 0.286 µm and 1.51 µm). The transition phenomena are observed when droplet train of We=349 and We=94.8 impinged onto a heated copper surface (from 150°C to 280°C). Though the general trend observed shows that the wetted area diameter and splashing rebound angle decreases as surface temperature increases across the different surface roughness. This observation is due to the Weber number as such trend could be seen across all three surface roughness. Furthermore, results obtained at the same temperature indicates that the wetted area diameter and splashing rebound angle tends to be larger at a higher Weber number. Similarly, such trend can be observed across the different surface roughness. Hence, the effect of surface roughness on such phenomena can be seen as negligible or small. For droplet train of We=94.8, formation of vapor bubbles occurs across all three surfaces at different surface temperature. The vapor bubbles were generated at 221.6˚C, 221.6˚C and 204.5˚C for surface roughness 0.136 µm, 0.286 µm and 1.51 µm respectively. Further investigation states that as the surface roughness decrease, the formation of such vapor bubbles will occur at a lower surface temperature. Lastly, the radius, rebound angle and linear velocity of the secondary droplets did not form a co-relation with the surface roughness as a common trend could not be observed.