Theoretical Model of Single Fiber Efficiency and the Effect of Microstructure on Fibrous Filtration Performance: A Review

Bai, Hedan; Qian, Xiaoming; Fan, Jintu; Shi, Yunlong; Duo, Yongchao; Guo, Changsheng; Wang, Xiaobo

doi:10.1021/acs.iecr.0c04400

Cited by 38 publications

(24 citation statements)

References 214 publications

(357 reference statements)

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“…It has been reported that particles in a nonuniform filter vary in moving velocity depending on the local structure characteristic. [44,45] A quality factor that takes pressure drop and filtration efficiency into account was used to evaluate filter performance…”

Section: Air Filtration Performance Of Single-layer Nanofibrous Membranesmentioning

confidence: 99%

Improvement of Air Filtration Performance Using Nanofibrous Membranes with a Periodic Variation in Packing Density

Liu

Shao

Wang

et al. 2021

Adv Materials Inter

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particulate matter (particle size > 10 µm), inhalable particulate matter (particle size < 10 µm), and fine particulate matter (PM 2.5 , equivalent diameter < 2.5 µm). [1] PM 2.5 particles are particularly harmful because they can be inhaled into the lungs and even enter the blood circulatory system, causing health issues. [2] PM 2.5 particles are also a good carrier of bacteria and viruses, resulting in the transmission of diseases, such as COVID-19. [3] Filtration with a filter is an effective method to remove these harmful particles and prevent the diseases from spreading.The removal mechanism of fibrous filters for these tiny particles mainly includes inertial collision, [4,5] direct interception, [6] diffusion effect, [7] gravity sedimentation, [8] and electrostatic attraction. [9] Nanofibrous filters have outstanding filtration efficiency due to the fine fiber diameters and high specific surface areas. [10] In addition, nanofibers have lower pressure drop due to the "slip effect" of their unique fiber diameter size, similar to the mean air molecule free path, reducing the airflow resistance. [11] Hence, nanofibers are widely used in air filtration, especially in air filters, [12][13][14] ventilating and air conditioning filters, [15] and masks. [16] Xia et al. [17] compared 122 nanofibrous filters with conventional heating, ventilation, and air-conditioning (HVAC) filters and showed that nanofiber filters had a higher quality factor than the conventional filters because of nanofibers' "slip effect."Considerable research has been devoted to understanding the structural parameters of nanofibers and their effect on filtration performance. For example, Wang et al. [18] studied the influence of nanofiber morphology on filtration performance. Zhang et al. [19] reported a pore size gradient combination of different nanofibrous membranes, which showed a filtration efficiency of 99.992% for 300 nm particles at a low-pressure drop. Li et al. [20] proposed a mathematical relationship between filtration efficiency and nanofibrous pore size. Bian et al. [21] established a semiempirical model to predict the influence of nanofiber diameter, membrane thickness, and packing density on the pressure drop of nanofibrous filters. Most studies have been based on nanofiber membranes with a homogenous distribution of nanofibers along the membrane.This study reports a patterned nanofibrous membrane and its novel filtration performance. The nanofibers are prepared using an electrospinning technique, and the nanofibers are collected on a commercial nonwoven fabric covering a roller collector, which is prepared using a metal sheet with a round hole array. The nanofibers collected on the metal surface have a much denser structure than those in the hole areas. As a result, the patterned nanofibrous membrane has a different filtration performance (lower pressure drop and filtration efficiency) from the uniform nanofiber membrane, prepared under the same condition but using a smooth roller collector. When two layers of this patterned nanof...

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Section: Air Filtration Performance Of Single-layer Nanofibrous Membranesmentioning

confidence: 99%

Improvement of Air Filtration Performance Using Nanofibrous Membranes with a Periodic Variation in Packing Density

Liu

Shao

Wang

et al. 2021

Adv Materials Inter

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“…Of course, the efficiency of single fiber is a function of the flow field. The classical fibrous filtration theory of single fiber follows Kuwabara–Happel single cell flow field consideration for array of parallel circular cylinders, which evolved from potential flow model by Albercht and Lamb’s viscous flow model [ 51 , 52 ]. Kuwabara hydrodynamic factor (Ku) was introduced to characterize the effect of fluid interference on the fibers, as stated in Equation (5) [ 51 , 53 , 54 , 55 ].…”

Section: Filtration Of Pms Using Ultrafine Fibersmentioning

confidence: 99%

“…However, Equation (9) was later modified by Payet as it was found that for lower Pe, the expression may predict >100% efficiency. Therefore,

is given by [ 52 ]

…”

Section: Filtration Of Pms Using Ultrafine Fibersmentioning

confidence: 99%

“…Interception coefficient (R) (

, where d p is particle diameter) was considered as the basis of efficiency measurement where flow rate coincides with fiber volume fraction [ 46 ]. There was hardly any parity found between theoretical SFFE for interception and the experimental results, until effect of neighboring fibers, packing density, limiting streamlines, and slip flow were taken into consideration [ 52 ]. Lee and Liu et al (1982) [ 61 ] proposed interception efficiency (

) given by Equation (12)

…”

Section: Filtration Of Pms Using Ultrafine Fibersmentioning

confidence: 99%

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Ultrafine PVDF Nanofibers for Filtration of Air-Borne Particulate Matters: A Comprehensive Review

Sanyal

Sinha-Ray

2021

Polymers

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The ongoing global pandemic has bestowed high priority uponthe separation of air-borne particulate matters (PMs), aerosols, etc. using nonwoven fibrous materials, especially for face masks as a means of personal protection. Although spunbond or meltblown nonwoven materials are amongst the forerunners for polymer microfiber-based face mask or air filter development in mass scale, relatively new process of nonwoven manufacturing such as electrospinning is gaining a lot of momentum amongst the filter membrane manufacturers for its scalability of nanofiber-based filter membrane fabrication. There are several nanofiber-based face masks developing industries, which claim a very high efficiency in filtration of particulate matters (PM0.1–10) as well as other aerosols for their products. Polyvinylidene fluoride (PVDF), which is commonly known for its use of tactile sensors and energy harvesters, due to its piezoelectric property, is slowly gaining popularity among researchers and developers as an air filter material. Electrospun PVDF nanofibers can be as fine as 50 nm in mass scale, which allows the membrane to have large surface area compared to its volume, enhancing nanofiber–PM interaction. At the same time, the breathability index can be improved through these PVDF nanofiber membranes due to their architectural uniqueness that promotes slip flow around the fibers. The conductive nature of PVDF makes it advantageous as a promising electret filter allowing better capturing of ultrafine particles. This review aims to provide a comprehensive overview of such PVDF nanofiber-based filter membranes and their roles in air filtration, especially its application in filtrate of air-borne PMs.

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“…Further, GeoDict has successfully generated virtual fibrous media with varying solid volume fraction and orientation distribution and performed simulations to study the dependence of permeability on the microstructural characteristics 34 , 35 . In a comprehensive review of theoretical filtration models, Bai et al 36 compared theoretical, simulated, and experimental data for different filtration mechanisms, including diffusion, interception, and impaction. These previous works show that numerical simulations can be a valuable tool for predicting the filtration performance of nonwoven materials.…”

Section: Introductionmentioning

confidence: 99%

Unfolding the effects of decontamination treatments on the structural and functional integrity of N95 respirators via numerical simulations

Sharma

Wang

Rao

et al. 2022

Sci Rep

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Filtering facepiece respirators (FFRs) provide effective protection against diseases spread through airborne infectious droplets and particles. The widespread use of FFRs during the COVID-19 pandemic has not only led to supply shortages, but the disposal of single-use facemasks also threatens the environment with a new kind of plastic pollution. While limited reuse of filtering facepiece respirators has been permitted as a crisis capacity strategy, there are currently no standard test methods available for decontamination before their repeated use. The decontamination of respirators can compromise the structural and functional integrity by reducing the filtration efficiency and breathability. Digital segmentation of X-ray microcomputed tomography (microCT) scans of the meltblown nonwoven layers of a specific N95 respirator model (Venus-4400) after treatment with one and five cycles of liquid hydrogen peroxide, ultraviolet radiation, moist heat, and aqueous soap solution enabled us to perform filtration simulations of decontaminated respirators. The computed filtration efficiencies for 0.3 µm particles agreed well with experimental measurements, and the distribution of particle penetration depths was correlated with the structural changes resulting from decontamination. The combination of X-ray microCT imaging with numerical simulations thus provides a strategy for quantitative evaluation of the effectiveness of decontamination treatments for a specific respirator model.

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Theoretical Model of Single Fiber Efficiency and the Effect of Microstructure on Fibrous Filtration Performance: A Review

Cited by 38 publications

References 214 publications

Improvement of Air Filtration Performance Using Nanofibrous Membranes with a Periodic Variation in Packing Density

Improvement of Air Filtration Performance Using Nanofibrous Membranes with a Periodic Variation in Packing Density

Ultrafine PVDF Nanofibers for Filtration of Air-Borne Particulate Matters: A Comprehensive Review

Unfolding the effects of decontamination treatments on the structural and functional integrity of N95 respirators via numerical simulations

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