Identification of Deposited Oil Structures on Thin Porous Oil Mist Filter Media Applying µ-CT Imaging Technique

Straube, Christian; Meyer, Jörg; Dittler, Achim

doi:10.3390/separations8100193

Cited by 17 publications

(4 citation statements)

References 24 publications

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“…Studies utilizing microscopy for characterizing challenged filter surfaces are scarce. Observation of "beading" morphologies was observed in several publications focusing on liquid-phase organic aerosols [82,85].…”

Section: Effect Of Smoke Loading On the Filtration Efficiency And Mor...mentioning

confidence: 95%

Evaluation of Filtration Efficiency of Various Filter Media in Addressing Wildfire Smoke in Indoor Environments: Importance of Particle Size and Composition

Shirman,

Liu

2023

Atmosphere

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Sub-micron particles are ubiquitous in the indoor environment, especially during wildfire smoke episodes, and have a higher impact on human health than larger particles. Conventional fibrous air filters installed in heating, ventilation, and air conditioning (HVAC) systems play an important role in controlling indoor air quality by removing various air pollutants, including particulate matter (PM). However, it is evident that the removal efficiency of wildfire smoke PM and its effect on filter performance is significantly under-studied. This study delves into the size-specific removal efficiency of pine needle smoke, a representative of wildfire smoke and emissions. We test an array of filter media with minimum efficiency reporting values (MERV) spanning 11–15. Both size-resolved particle number concentrations and mass concentrations were measured using an Optical Particle Sizer (OPS, TSI, Inc.) and a Scanning Mobility Particle Sizer (SMPS, TSI, Inc.). Furthermore, we characterize the filter media morphology and smoke particles deposited on filter fibers using Scanning Electron Microscopy (SEM) to gain insights into the interaction dynamics of these particles. Our findings add to the comprehension of the relationship between MERV designations and smoke removal efficiency. Such insight can inform standards and guidelines and equip decision-makers with the knowledge needed to initiate measures for mitigating the impact of air pollution, specifically on the indoor environment.

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Section: Effect Of Smoke Loading On the Filtration Efficiency And Mor...mentioning

confidence: 95%

Evaluation of Filtration Efficiency of Various Filter Media in Addressing Wildfire Smoke in Indoor Environments: Importance of Particle Size and Composition

Shirman,

Liu

2023

Atmosphere

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“…µ-CT scans presented in this publication were generated with a ZEISS Xradia 520 Versa. A detailed description of its functionality and use can, for example, be found in the work by Straube et al [19]. A sample of 0.5 cm × 2 cm was cut out of the filter.…”

Section: Post-experimental Analysis and Reference Filtersmentioning

confidence: 99%

Penetration of Water-Soluble Material through Gas-Cleaning Filters

2022

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To predict the behavior of gas-cleaning filters during real-world operation, it is essential to understand their response to ambient conditions. The temporary presence of water droplets in gas-cleaning filtration systems due to fog, spray rain, or condensation, as examples of irregular events, has an impact on the filters’ operating performance, especially when soluble particles are present. In this work, surface filters were loaded with mixtures of water-soluble salt particles and insoluble glass spheres. These were, subsequently, exposed to water mist and dried by a particle-free gas stream. A novel approach to analyze the drainage of solution on filters with soluble filter cakes is presented, which allows the detection of solubles on the clean gas side of the filter. As a result, this work, for the first time, presents a sighting of the penetration of soluble filter cake material through gas-cleaning filters. Furthermore, filter performance, in terms of differential pressure and fractional separation efficiency, was determined and a characteristic differential pressure evolution for hydrophilic filters during exposure to water mist was also identified. The fractional separation efficiency of gas-cleaning filters decreases due to exposure to water mist. The findings are supported by scanning electron microscopy (SEM) images, energy-dispersive X-ray (EDX), and X-ray microtomography (µ-CT analysis) images.

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“…Droplet-shaped liquid structures (clamshell and barrel shaped droplets) are formed as well as so-called liquid sails. Liquid sails can be spanned between adjacent fibers, when enough liquid is accumulated, which cover often a larger area inside the filter [8]. The resulting structures and the deposition behaviour depend on the media properties of the fiber (pore size, fiber diameter, fiber orientation, wetting behaviour), the fluid properties (viscosity, density, surface tension) and operating parameters (temperature, pressure, gas velocity).…”

Section: Introductionmentioning

confidence: 99%

“…This mechanism has been observed by many other investigations. Many of the investigations focused on the filter performance or the resulting liquid structure [1,8,18,19]. Mead-Hunter et al [19] simulated for a portion of a coalescing filter the processes steps of droplet capture, coalescence, film break-up, and the motion of coalesced liquid droplets in coalescing filters.…”

Section: Introductionmentioning

confidence: 99%

Experimental Analysis of Fundamental Water Droplet Coalescence Mechanisms on a Single Vertical Fiber

Schwarzwälder

Dittler

Meyer

2022

Preprint

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In mist filtration, fiber-based coalescers are an established form of filtering droplets contained in mist. The filtration process can be divided into different process steps, describing the impact of the droplets on fibers, the liquid transport, and the formation of fluid structures. According to the current state of knowledge, the transport of fluid along the fibre is caused by gravitational draining, pressure, shearing, and electrostatic forces. The formation of fluid structures includes the creation of larger droplets by coalescing and fluid sails between adjacent fibres [1–3]. In order to investigate mechanisms inside depth filters on a microscopic level, investigations are often reduced to single fibers [1, 4–6]. Zhang et al. [7] observed self-propelled detachment of coalesced droplets which were arranged side by side on identical axial position. In this work, the coalescence mechanisms of axial distributed water droplets on a vertical fiber, subjected to gravity, are investigated. This is done with the latest high-speed camera technology commercially available. Automated tracking of droplets is used for a frame-by-frame investigation of droplet position, size, and oscillation behaviour. Characteristic coalescence mechanisms are reported and describe the process of fluid formation. The first coalescence mechanism is identified by the coalescence of droplets contained in mist with an adhering droplet at the fiber. The second coalescence mechanism describes the coalescence of two closely spaced sessile droplets on a fiber. As a result, the newly formed droplet oscillates and can begin to drain. Furthermore, the coalescence mechanism of a draining and sessile droplet is investigated. Additional observed mechanisms describe the process of droplet transportation. These mechanisms are: gravitational draining, droplet bouncing, and droplet sweeping.

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Identification of Deposited Oil Structures on Thin Porous Oil Mist Filter Media Applying µ-CT Imaging Technique

Cited by 17 publications

References 24 publications

Evaluation of Filtration Efficiency of Various Filter Media in Addressing Wildfire Smoke in Indoor Environments: Importance of Particle Size and Composition

Evaluation of Filtration Efficiency of Various Filter Media in Addressing Wildfire Smoke in Indoor Environments: Importance of Particle Size and Composition

Penetration of Water-Soluble Material through Gas-Cleaning Filters

Experimental Analysis of Fundamental Water Droplet Coalescence Mechanisms on a Single Vertical Fiber

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