Pan Zhengyuan, Ou Qisheng, Romay Francisco J, Chen Weiqi, Liang Yun, Pui David Y H
Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN, 55455, USA.
State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, 510640, China.
Small. 2024 Dec;20(50):e2406619. doi: 10.1002/smll.202406619. Epub 2024 Oct 2.
Nanofiber filters are widely used in air filtration applications due to their superior performance over microfiber filters. Velocity slip around nanofibers has been identified as a key factor contributing to their high figure of merit, yet its impact on filter performance, especially particle collection efficiency, remains unclear due to the difficulty in isolating the slip effect as the sole variable. This study combines experimental and simulation methods to investigate the slip effect by adjusting the air molecule mean free path, rather than varying fiber size as done in previous studies. Filter media with mean fiber sizes ranging from 16.2 to 0.084 µm are utilized. An image-based regression method is developed to address the challenge of determining the solidity of thin nanofiber layers. The results show that the slip effect is enhanced as the testing pressure decreases, reducing pressure drop by less than 15% for microfiber filters and over 50% for nanofiber filters ≈100 nm. The enhanced slip effect at low pressures (i.e., relatively low pressure compared to the ambient environment) significantly improves filtration efficiency, especially for particles larger than 100 nm. It also proposes semi-empirical equations for predicting filter performance in slip and transition flow regimes.
纳米纤维过滤器因其相对于微纤维过滤器的卓越性能而广泛应用于空气过滤领域。纳米纤维周围的速度滑移已被确定为其高品质因数的关键因素，然而由于难以将滑移效应作为唯一变量分离出来，其对过滤性能，尤其是颗粒收集效率的影响仍不明确。本研究结合实验和模拟方法，通过调整空气分子平均自由程来研究滑移效应，而不是像以往研究那样改变纤维尺寸。使用了平均纤维尺寸范围为16.2至0.084微米的过滤介质。开发了一种基于图像的回归方法来应对确定薄纳米纤维层密实度的挑战。结果表明，随着测试压力降低，滑移效应增强，微纤维过滤器的压降降低不到15%，而约100纳米的纳米纤维过滤器的压降降低超过50%。在低压下（即相对于环境而言压力较低）增强的滑移效应显著提高了过滤效率，尤其是对于大于100纳米的颗粒。研究还提出了用于预测滑移和过渡流态下过滤性能的半经验方程。
