The rate of drying of moisture from a metal surface and its implication for time of wetness

A model of the evaporation of water and saline solutions from a metal surface is developed. The evaporation of a droplet of moisture from a flat metal plate over which a uniform laminar flow of air occurs is modelled by assuming an analogy between heat and mass transfer. The model is adjusted to predict the evaporation of a saline solution under the assumption that the presence of the salt affects only the vapour pressure. The predictions of the model are compared with observed experimental evaporation rates and are found to be of reasonable accuracy. Predicted drying times for moisture films under conditions typical of those associated with building microclimates are determined. The implications of these drying times to the traditional estimation of time of wetness are assessed.