STUDY ON COOLING MIST SPRAY CHARACTERISTICS AND CAVITATION INFLUENCE

Spray or nozzle have many engineering applications, such as in combustion system, agriculture and industrial process, dust control, firefighting, spray drying and evaporative cooling. This research was carried out to study the spray characteristics of commercial water cooling mist sprays (nozzle diameter of 1mm and 2mm), and the effect of cavitation on the characteristics of the spray. The spray angle, droplet velocity and droplet size of each nozzles were taken by the means of direct photography using high speed camera and digital still camera. Next, cavitation phenomenon was simulated by CFD software (ANSYS) and its relation to the results from experiment was established. Results show that, the higher the supply pressure, the stronger the cavitation that occurs. This is shown by the value of minus pressure that generated inside the nozzle. This in turn effect the spray droplet size, where it is proven that higher supply pressure produced smaller droplets. Results also shown that with longer nozzle length, the cavitation can become more significant, until reaching certain threshold. This suggests that there is a relation of L/D (nozzle length to diameter ratio) that governs the cavitation formation.