Studies on the evaporation of crude oil and petroleum products - II. Boundary layer regulation

Experiments were conducted to determine if oil and petroleum evaporation is regulated by the saturation of the air boundary layer. Experiments included the examination of the evaporation rate with and without wind. It was found that evaporation rates were similar for all wind conditions, but lower for the no-wind conditions. Experiments where the area and mass varied showed that boundary layer regulation was not dominant for petroleum products. Under all experimental and environmental conditions, oils or petroleum products were not found to be strictly boundary-layer-regulated. Experiments on the rate of evaporation of purl compounds showed that those larger than decane were not boundary-layer-regulated. Many oils and petroleum products contain few compounds smaller than decane, and this explains why their evaporation is not strictly boundary-layer-limited. Comparison of the air saturation levels of various oils and petroleum products shows that the saturation concentration of water, which is strongly boundary-regulated, is significantly less than that of several petroleum hydrocarbons. Lack of boundary layer regulation for oils, after a short initial time period, is shown to be a result of both this higher saturation concentration, as well as a low (below boundary layer value) evaporation rate. (C) 1998 Elsevier Science B.V.