This study presented a comprehensive gas permeation model to predict the skin parameters of a complex system, specifically a hollow fiber membrane with an asymmetric structure consisting of two external and internal skin layers. According to the work of Haefer for segments of pores connected in series as in hollow fiber membranes, applying the Wakao et al. model, a comprehensive model for the transition regime was derived. The model was examined against the various fabricated PES and PEI hollow fiber membranes. Unlike conventional models, the proposed method predicted the mean pore size and mean pore length independent of surface porosity for each skin layer. The study revealed valuable insights into i) the middle pressure, ii) the difference between the skin parameters of the two membrane skins, and iii) the impact of the feeding direction on gas permeation behavior. It was shown that the dependency of permeation behavior on the feeding direction is linked to the influence of middle pressure on viscous flow, which is closely related to surface porosities of each side. It is evident that even the slightest variations in the fabrication parameters can result in different structures. Furthermore, it is evident that the assumption of neglecting slip flow was reasonable within the experienced Knudsen number range. The model also highlighted that the skin parameters of the two skin layers may not be identical, a distinction not captured by the current models. The traditional approach of setting the middle pressure as the average of the upstream and downstream pressures has been improved by expressing it as a linear function of both pressures. In the feed side, higher pressures led to dominant viscous flow, whilst the permeate side was more influenced by the free molecular regime due to lower pressures. There existed a competition between the Knudsen flow and the viscous flow at a specific Knudsen number for the feeding side pores, whether it was the inner or outer surface. The finding emphasized the significance of porosity values on each side in determining the proximity of middle pressure to feed and permeate side pressures, underscoring the importance of accurate knowledge of surface porosities, mean pore sizes, and pore lengths for both skin layers in understanding processes involving porous dual-skin hollow fiber membranes.

中文翻译：

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双皮不对称中空纤维微孔膜建模，通过气体渗透测试分别预测皮参数

这项研究提出了一个综合气体渗透模型来预测复杂系统的表皮参数，特别是具有由两个外部和内部表皮层组成的不对称结构的中空纤维膜。根据 Haefer 对中空纤维膜中串联连接的孔段的研究，应用了 Wakao 等人的方法。模型，导出了过渡制度的综合模型。该模型针对各种制造的 PES 和 PEI 中空纤维膜进行了检查。与传统模型不同，所提出的方法预测了独立于每个皮肤层的表面孔隙率的平均孔径和平均孔径长度。该研究揭示了以下方面的宝贵见解：i) 中间压力，ii) 两个膜皮的表皮参数之间的差异，以及 iii) 进料方向对气体渗透行为的影响。结果表明，渗透行为对进料方向的依赖性与中间压力对粘性流的影响有关，而粘性流与各面的表面孔隙率密切相关。显然，即使制造参数最微小的变化也可能导致不同的结构。此外，很明显，忽略滑流的假设在经验的努森数范围内是合理的。该模型还强调，两个皮肤层的皮肤参数可能不相同，当前模型未捕捉到这一区别。将中间压力设置为上游和下游压力的平均值的传统方法已得到改进，将其表示为两个压力的线性函数。在进料侧，较高的压力导致粘性流占主导地位，而渗透侧由于压力较低而更容易受到自由分子状态的影响。在特定的努森数下，无论是内表面还是外表面，对于进料侧孔，努森流和粘性流之间都存在竞争。该发现强调了每一侧的孔隙率值在确定中间压力与进料侧压力和渗透侧压力的接近程度方面的重要性，强调了准确了解两个表层的表面孔隙率、平均孔径和孔隙长度在理解涉及的过程中的重要性。多孔双层中空纤维膜。