Liquid agent transport was investigated around an unheated and heated cylinder (to a near-surface temperature of approximately 423 K) under ambient conditions. Experimental results are presented for a well-characterized, droplet-laden homogenous turbulent flow field, using water, HFE-7100 (with a boiling point of 334 K), and HFE-7000 (with a boiling point of 307 K). Phase Doppler interferometry and visualization techniques were used to explore the thermal effects on droplet surface impingement, vaporization, and transport around and downstream behind the cylinder, by providing information of droplet size and velocity in the vicinity of a cylinder. Results indicated that droplets larger than 30 mm - 50 mm tend to impinge on the cylinder surface or disperse around the cylinder to be transported far downstream of the obstacle. Impinging droplets generally coat the surface with few droplets rebounding back into the free stream. Downstream in the wake region of the cylinder, smaller size droplets (generally, of less than 30 mm) are entrained into the recirculation zone. Near the heated cylinder surface, thermal effects reduce droplet mean size significantly. Liquid impingement, coating, and dripping were eliminated for the lower boiling point HFE agents due to rapid vaporization. Droplet mean size decreased and velocity increased with lower boiling point agents.
Proceedings Title: 19th Annual ILASS-Americas Conference Institute for Liquid Atomization and Spray Systems
Conference Dates: May 23-26, 0006
Conference Location: Toronto,
Pub Type: Conferences
computational fluid dynamics, droplet transport, fire suppression, halon alternatives, homogeneous turbulent flow, model validation, phase Doppler interferometry