ISSN Online: 2377-424X
International Heat Transfer Conference 12
Freezing of supercooled water droplets impinging upon solid surfaces
Sinopsis
Freezing behavior of supercooled water droplets impinging upon solid surfaces was experimentally studied. Each droplet of 2−3 mm in diameter was supercooled on a water-repellent guideway in a dry nitrogen-gas ambience adjusted to −10°C or −15°C, then blasted horizontally by a jet of pressurized nitrogen gas to impinge upon the vertical surface of a thick block made of aluminum or poly(methyl methacrylate). The behavior of the impact against the block surface and of the deformation and freezing of the droplet were observed using a high-speed videocamera. Different freezing modes were recognized to occur depending on the supercooling, the material of the block, and the finishing/treatment of the block surface. Immediate freezing inception (within 10 ms after the impact) of droplets occurred only on aluminum blocks at the lower temperature, −15°C, more preferably on a roughened surface than on a polished one. The block surface coated with a water-
repellent polymer layer made the droplets bounce back before the inception of freezing even at −15°C; this
finding indicates the potential of such coatings for preventing icing due to droplet freezing.