The effect of pressure and frequency on the dynamic behavior and evaporation time of successive water droplets impacting onto hot surface

Multiple droplets are the drop of water which continuously dropped on a surface in certain time difference. The phenomenon droplets impacting a solid surface can be found in a various field, one of them is the cooling process in the metal industry. The cooling process is carried out by spraying a number of water droplets to hot surface until it reaches the desired condition. When droplets impinge on the surface, the dynamics of droplets, such as the spreading and recoil phenomena, depend on some properties. In this study, the effect of pressure and drop frequency to the droplet characteristics as well as cooling effectiveness will be investigated. Visualization process is used to find maximum spreading which can indicate the effectiveness of hot surface cooling. The experiment is performed by setting the distance of water tank and nozzle into 100cm, 150cm and 200cm while the frequency of droplets is set at 245, 386, and 623 drops/minute. The material used in the present work is Stainless Steel with the temperature ranged from 100°C - 220°C. In addition, image processing technique is applied to gather the quantitative data from the images that successfully taken by using high-speed camera. Based on the study, it is found that the pressure of water tank affects the frequency of generated droplet. Furthermore, the frequency of droplet impacting onto the hot surface also influences the evaporation time.