St. Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg 199034, Russia.
J Chem Phys. 2018 Jun 21;148(23):234103. doi: 10.1063/1.5026399.
A new kinetic analysis of degassing and swelling of a decompressed liquid solution with several dissolved gases has been presented. The analysis has been performed for the nucleation stage of formation and growth of supercritical gas bubbles in a closed system under conditions of a limited availability of the dissolved species. The nucleation stage is an important stage of degassing, on which a certain size distribution of gas bubbles is formed, being the starting point for further growth. This stage starts with the appearance of supercritical gas bubbles and is widely completed when the nucleation rate of supercritical gas bubbles diminishes by a decimal order. Neglecting the role of the Laplace pressure in large supercritical bubbles, we were able to introduce the concept of total gas supersaturation and to develop a theory of this stage for liquid solutions with arbitrary number and any values of supersaturations and solubilities of the dissolved gases. First, we have considered slowly growing bubbles within the mean-field approach assuming a stationary diffusion of gases to bubbles at moderate total gas supersaturation. In the case of large total gas supersaturation, we have built a description of fast growing bubbles on the basis of the extended excluded volume approach with nonstationary nonuniform diffusion shells around the bubbles and mean-field mixing of the concentration of gases at the external boundaries of the shells. A main novel feature of the developed theory is its ability to predict the kinetic behavior of the whole ensemble of bubbles with different sizes under changes in the initial gas composition in the liquid solution at its fast decompression. It has been shown that the effects of nonstationary diffusion may be very significant in the growth of multicomponent bubbles and, in particular, are responsible for a significant swelling of a decompressed liquid solution. Distribution of supercritical bubbles in sizes as a function of concentrations of solute gases at any moment of the nucleation stage, the duration of the nucleation stage, and the swelling ratio at the end of the nucleation stage have been determined.
已提出一种新的动力学分析方法，用于研究具有多种溶解气体的减压液体溶液的放气和膨胀。该分析是在溶解物质有限可利用的条件下，针对封闭系统中超临界气泡形成和生长的成核阶段进行的。成核阶段是放气的重要阶段，在此阶段形成了一定大小分布的气泡，这是进一步生长的起点。该阶段始于超临界气泡的出现，并在超临界气泡成核速率减小一个数量级时广泛完成。在忽略大超临界气泡中的拉普拉斯压力的作用下，我们能够引入总气体过饱和度的概念，并为具有任意数量和任何溶解气体过饱和度和溶解度的液体溶液发展该阶段的理论。首先，我们在中等总气体过饱和度下，采用平均场方法考虑了缓慢生长的气泡，假设气体向气泡的扩散是稳定的。在总气体过饱和度较大的情况下，我们基于扩展的排斥体积方法，建立了快速生长气泡的描述，其中包括气泡周围的非稳态非均匀扩散壳和壳外部边界处气体浓度的平均场混合。所开发理论的一个主要新颖特征是其能够预测在液体溶液快速减压时初始气体组成变化下，不同大小的整个气泡系综的动力学行为。结果表明，非稳态扩散的影响在多组分气泡的生长中可能非常显著，特别是在减压液体溶液的显著膨胀中起作用。在成核阶段的任何时刻，都可以确定不同尺寸的超临界气泡的分布情况、成核阶段的持续时间以及成核阶段结束时的膨胀比作为溶质气体浓度的函数。
