Abstract
Various concepts for oil evaporation prediction are summarized. Models can be divided into those models that use the basis of air-boundary-regulation or those that do not. 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, in which case it was found that evaporation rates were similar for all wind conditions and no-wind conditions. Experiments where the area and mass varied showed that boundary-layer regulation was not governing for petroleum products. Under all experimental and environmental conditions, oils or petroleum products were not found to be boundary-layer regulated. Experiments on the rate of evaporation of pure compounds showed that compounds 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 air 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 air boundary-regulated, is significantly less than that of several petroleum hydrocarbons. Lack of air boundary-layer regulation for oils is shown to be a result of both this higher saturation concentration as well as a low (below boundary-layer value) evaporation rate.
Highlights
Evaporation is an important process for most oil spills
The results of the following experimental series have shown the lack of boundary-layer regulation: 1) a study of the evaporation rate of several oils with increasing wind speed shows that the evaporation rate does not change measurably with wind level
Known to be boundary-layer regulated, does show a significant increase with wind speed, U (Ux, where x varies from 0.5 to 0.78, depending on the turbulence level); 2) the volume or mass of oil evaporating correlates with the evaporation rate
Summary
Evaporation is an important process for most oil spills. In a few days, typical crude oils can lose up to 45% of their volume. If the evaporation of oil was like that of water and was air boundary-layer regulated, one could write the mass transfer rate in semi-empirical form. This assumption was never tested by experimentation, as revealed by a literature search [2] The implications of these assumptions are that evaporation rate for a given oil is increased by: increasing turbulence, increasing wind speed, and increasing the surface area of a given mass of oil. These factors can be verified experimentally to test if oil is boundary-layer regulated or not. These factors formed the basis of experimentation for this paper
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