Simulation of Freezing and Frozen Precipitation for the Evaluation of De/anti-icing Systems

Simulating freezing and frozen precipitation in an indoor laboratory setting can permit year round evaluation of de/anti-icing systems and fluids. At AMIL, freezing rain, freezing drizzle, icing fog and in-cloud icing as well as frost, snow, ice pellets and icing clouds can be simulated in a variety of cold chambers of different heights and with different wind conditions using specialized spraying systems and temperature set-ups. Freezing rain is simulated using a 9 m high vertical chamber capable of supercooling water droplets from 100 to 1000 μm, so they freeze not long after impact. The freezing drizzle is simulated in a 4 m high chamber where supercooled droplets from 50 to 250 μm freeze on impact. Icing fog and in-cloud icing are simulated with the help of a pneumatic spray nozzle system which allows for a finer water spray, in the 20 μm diameter range. The frost is simulated by saturating a cold room with humidity generated from a heated, temperature controlled water bath. Snow is simulated with a fine pneumatic water spray which forms a soft rime simulating the effect of natural snow. Ice pellets are made in the 9 m high vertical cold chamber using strong turbulent wind that increases the air residency and convective air cooling of water droplets so they freeze before impact. Finally, icing wind tunnels allow for the simulation of an object iced through a passing supercooled cloud. For all simulations, humidity can be controlled by using a heated water bath to increase it, or by using an independent refrigeration unit or molecular sieves to decrease it. This paper reviews the various simulated precipitation obtained at AMIL.