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Experimental and theoretical study on multicomponent diffusion of gases under rarefied conditions

稀薄条件下气体多组分扩散的实验与理论研究

基本信息

批准号：
253170578
负责人：
Professor Dr.-Ing. Jorg Thöming, since 1/2016
金额：
--
依托单位：
Fachgebiet Verfahrenstechnik der Wertstoffrückgewinnung (VdW) (aufgelöst)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2014
资助国家：
德国
起止时间：
2013-12-31 至 2015-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/253170578?language=en
关键词：
Experimental theoretical study multicomponent diffusion

项目摘要

Multicomponent diffusion of gases in micro scale and nanoscale confined geometries is determining the integral behavior and efficiency of many natural and technical processes. In such small systems the gas is in a state referred to as rarefied where diffusion is the dominating, and hence limiting, transport mechanism. Considerable enhancement on the macroscale in, e.g., membrane gas separation, heterogeneous catalysis, and microelectromechanical systems is only possible when understanding the dependence of gaseous rarefaction on multicomponent diffusion fundamentally. The Maxwell-Stefan equations (MSE) yield reasonable results for bulk multicomponent diffusion but fail for the description of transport under rarefied conditions. Runstedtler's approach from 2006 superimposes bulk diffusion and Knudsen diffusion to the MSE. However, in this approach surface diffusion is disregarded which, according to my own work, under higher orders of rarefaction is the dominating diffusion mechanism. The nowadays accepted Binary Friction Model (BFM) contains a correction factor that accounts for the transition between the continuum regime and the free molecular regime. This indicates that the BFM does not fully explain the mechanisms yet, and potential for improvement is given. Furthermore, in literature all experimental and numerical analysis on multicomponent diffusion confine on uniform ducts as object of examination. This is wondrous since 'real' pores are mostly tapered and diffusive flux strongly depends on the duct's cross-sectional area as it was shown in an own earlier work. This project aims for a new, experimentally validated model that allows for the prediction of multicomponent diffusion in uniform and tapered ducts over a wide range of gaseous rarefaction.

气体在微尺度和纳米尺度受限几何结构中的多组分扩散决定了许多自然和技术过程的整体行为和效率。在这样的小系统中，气体处于被称为稀薄的状态，其中扩散是主要的，因此是限制性的传输机制。在宏观尺度上有相当大的提高，例如，膜气体分离、多相催化和微机电系统只有在从根本上理解气体稀薄对多组分扩散的依赖性时才是可能的。麦克斯韦-斯特凡方程（MSE）对体相多组分扩散产生了合理的结果，但无法描述稀薄条件下的输运。Runstedtler在2006年的方法将体扩散和努森扩散叠加到MSE。然而，在这种方法中，表面扩散被忽略，根据我自己的工作，在更高的稀疏阶数下，表面扩散是主要的扩散机制。目前公认的二元摩擦模型（BFM）包含一个修正因子，该因子解释了连续区和自由分子区之间的过渡。这表明BFM还没有完全解释这些机制，并给出了改进的潜力。此外，在文献中，所有的实验和数值分析的多组分扩散限制在均匀管道作为检查对象。这是令人惊奇的，因为“真实的”孔隙大多是锥形的，扩散通量强烈依赖于管道的横截面积，正如在自己的早期工作中所示。该项目的目的是一个新的，实验验证的模型，允许在广泛的气体稀薄均匀和锥形管道中的多组分扩散的预测。