Experimental Setup Simulating Hoarfrost Formation on Roadways

Abstract

Hoarfrost on roadways and bridges can cause slippery and dangerous conditions for motorists. To reduce the costs and environmental impact of countermeasures, road authorities wish to optimize their winter maintenance operations. To support this, good knowledge of the hoarfrost formation process is required. This paper presents a laboratory setup designed and built to study hoarfrost formation in detail under controlled conditions. The accumulation of hoarfrost and the stability of the main controlling parameters (air temperature, surface temperature, and relative humidity) are quantified. By using an open-loop wind tunnel with warm, humid air flowing over a cold stone surface, we produced conditions similar to those of frost formation on a road with good stability. The hoarfrost growth rates were found to be within the range of field measurements published previously. The growth rates were constant during each test and were directly related to the driving force created by the difference in the water vapor pressure in the air and at the stone surface.