We report on a steady-state based, and hence highly accurate numerical modelling study of the effect of the top and bottom wall in the current generation of micro-pillar array columns. These have a mesoporous retention layer that not only covers the pillar walls but also the bottom wall. Our results show that the performance of these columns can in general not be improved by also covering the top wall with the same layer, despite the increased column symmetry this approach would offer. The reason for this is that the local species retardation caused by a retentive layer is much stronger than the pure flow arresting effect of an uncovered wall. At least, this has a crucial impact in high aspect-ratio systems such as micro-pillar array columns because these require a small inter-pillar distance to promote mass transfer together with a large channel depth to enable a sufficiently high flow rate. On the other hand, a notable improvement could be made if micro-pillar array would be produced without having a retentive layer at the bottom. At Péclet number Pe = 50 and aspect ratio AR = 5 for flow-channels, this gain amounts up to about 4.5 h-units at a zone retention factor k’’ = 2 and 1.75 h-units at k’’ = 16 (gain scales almost linearly with Pe).

中文翻译：

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微柱阵列柱及相关高纵横比色谱系统顶壁和底壁的贡献

我们报告了基于稳态的、因此高度准确的数值模拟研究，研究了当前一代微柱阵列柱的顶壁和底壁的影响。它们具有介孔保留层，不仅覆盖柱壁而且还覆盖底壁。我们的结果表明，尽管这种方法可以增加柱的对称性，但通常也不能通过用相同的层覆盖顶壁来提高这些柱的性能。其原因是由滞留层引起的局部物质阻滞比未覆盖的壁的纯阻流效果强得多。至少，这对高纵横比系统（例如微柱阵列柱）具有至关重要的影响，因为这些系统需要较小的柱间距离来促进传质，同时需要较大的通道深度以实现足够高的流速。另一方面，如果在底部没有保持层的情况下生产微柱阵列，则可以取得显着的改进。当流道的佩克莱特数 Pe = 50 且纵横比 AR = 5 时，区域保留因子 k'' = 2 时的增益可达约 4.5 h 单位，k'' = 16 时增益可达 1.75 h 单位（增益几乎与 Pe 成线性比例）。