Abstract

The characteristic features of the diffusion of helium and nitrous oxide diluted by propane to the same extent are experimentally studied at different pressures and concentrations of the diluent gas in the mixture. It is found that, at a certain pressure, convection currents appear in the system which intensify the partial mass transfer, which uncommon for diffusion. An increase in pressure intensifies the mixing of the components of the mixture. An increase in the concentration of the diluent gas in the mixture leads to the stabilization of convection modes. Solving diffusion equations shows that, in systems with a ballast gas, conditions for the nonlinear distribution of the concentrations of the components of the mixture along the length of the channel are implemented which can lead to the appearance of an extremum of the density of the mixture (i.e., inversion of the density gradient of the mixture), which induces the appearance of convection currents. The stability of the mechanical equilibrium of the ternary mixture in a vertical cylindrical channel under the action of gravity and at the predefined concentration gradients of the components is numerically studied. The boundary of the diffusion–convection kinetic transition is determined. The experimental and numerical results are compared in the coordinates of the Rayleigh number and pressure.

中文翻译：

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在具有稀释气体的三元混合物中改变扩散-对流模式

摘要

实验研究了在不同压力和混合物中稀释气体浓度下，丙烷稀释的氦气和一氧化二氮扩散至相同程度的特征。发现在一定压力下，系统中会出现对流，这种对流会加剧部分质量传递，这对于扩散是不常见的。压力的增加增强了混合物中各组分的混合。混合物中稀释气体浓度的增加导致对流模式的稳定。求解扩散方程式表明，在带有压载气体的系统中，沿着通道的长度实现了混合物成分浓度的非线性分布的条件，这可能导致出现混合物密度的极值（即，混合物密度梯度的倒置），引起对流的出现。数值研究了垂直圆柱通道中三元混合物在重力作用下和组分的预定浓度梯度下的机械平衡稳定性。确定了扩散-对流动力学转变的边界。在瑞利数和压力的坐标下比较了实验结果和数值结果。数值研究了垂直圆柱通道中三元混合物在重力作用下和组分的预定浓度梯度下的机械平衡稳定性。确定了扩散-对流动力学转变的边界。在瑞利数和压力的坐标下比较了实验结果和数值结果。数值研究了垂直圆柱通道中三元混合物在重力作用下和组分的预定浓度梯度下的机械平衡稳定性。确定了扩散-对流动力学转变的边界。在瑞利数和压力的坐标下比较了实验结果和数值结果。