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首页> 外文期刊>International Journal of Heat and Mass Transfer >Correlation for the convective and diffusive evaporation of a sessile drop
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Correlation for the convective and diffusive evaporation of a sessile drop

机译：固着液滴对流蒸发和扩散蒸发的相关性

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摘要

A simple correlation is developed to compute the evaporation rates of sessile drops and small puddles which are evaporating under the influences of both diffusion and natural convection of the vapor-air mixture surrounding the drop. The correlation is based on experiments conducted with eight hydrocarbons, which provide a factor of 16.6 variation in volatility as indicated by the equilibrium vapor pressures, a factor of 3.6 variation in molecular mass, and a factor of 2.2 variation in mass diffusivity, and thus the correlation is applicable for liquids having a broad range of properties. The correlation predicts the evaporation rates to within a root-mean-square (RMS) error of 6.5% over the broad range of conditions. Limitations of the correlation are investigated, and when one of the species is excluded, the RMS error is reduced to 4.9%. There are two main differences between this new correlation and the correlations that have been published previously. The first difference is the new correlation reduces to an expression for diffusion-limited evaporation as the density difference between the vapor-air mixture at the surface of the drop and the ambient air becomes negligible, or when the drop size becomes very small. The second difference is the form of the dependency on the density difference ratio, which in previous correlations is obtained solely through the Rayleigh number (Ra). This new correlation contains a term which represents the influence of natural convection on the evaporation rate and this term provides insight into the nature of the coupling of the diffusive and convective transport of the vapor.
机译：建立了一种简单的相关性，以计算在液滴周围的蒸气-空气混合物的扩散和自然对流的影响下，无蒂液滴和小水坑的蒸发速率。相关性是基于对八种碳氢化合物进行的实验得出的，这些碳氢化合物的挥发性由平衡蒸汽压指示为16.6的变化，分子质量为3.6的变化，质量扩散系数为2.2的变化，因此相关性适用于具有广泛特性的液体。该相关性预测在宽范围的条件下，蒸发速率将在均方根（RMS）误差内达到6.5％。研究了相关性的局限性，当排除其中一种时，RMS误差降至4.9％。这种新的相关性与以前已经发布的相关性之间有两个主要区别。第一个差异是新的相关性简化为扩散受限蒸发的表达式，因为液滴表面的蒸气-空气混合物与周围空气之间的密度差可以忽略不计，或者当液滴尺寸变得非常小时。第二个差异是对密度差异比的依赖形式，在以前的相关中，仅通过瑞利数（Ra）获得。这个新的相关性包含一个代表自然对流对蒸发速率的影响的术语，该术语提供了对蒸气的扩散和对流传输耦合的本质的了解。

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