An Analysis of Frost Formation on Vehicle Windows

Modern vehicles are expected to both be able to provide thermal comfort and to insure visibility for safe driving by preventing frost formation on the windows even at temperatures of below −20°C. Frost formation is the phenomenon resulting from breathed vapor which saturates along the inner surface of the windows at below 0°C and prevents the penetration of light from outside. To analyze the formation of frost on vehicle windows, the air flow in the compartment that controls the transfer of breathed vapor and the local air flow along the inner surface of the windows were observed using a herium bubble tracing method. The frost point and temperature distribution of the air in the compartment were measured for making a quantitative evaluation of vapor saturation

As the result of this study, engineering techniques for optimizing the structure of a cowl to effective utilize ram pressure, a defroster nozzle to cover the surface of the windows with hot dry air, and a drafter to prevent air stirring in the compartment were obtained. A prototype vehicle incorporating these developments was built and tested under low-temperature conditions. The test results verified the high performance of the defroster and confirmed that a comfortable interior climate was obtained.