Low-cost PM sensors are widely applied in the field of particle immision measurement. In addition, they are already established in the application of emission characterization for the detection of temporal and local particle concentration. Due to those characteristics, low-cost PM sensors represent a promising approach for the use in autonomous process control and process management of dedusting systems.

For an effective process control and process management of dedusting systems, the characterization of particle properties (particle concentration and particle size distribution) is one of the key issues. Real-time access to relevant process parameters (particle concentrations and particle size distributions), e.g. by in-situ-measurements, is not feasible at the present development stage. The measurement of the particle properties should take place directly in the process (in-line). Therefore, in contrast to high-cost sensors, which cost above 20.000 EUR and are mainly suited for laboratory applications, particle measurement technologies available at reasonable costs are needed. For this reason, low-cost PM sensors for in-situ-measurement of particle concentrations and particle size distributions are to be investigated fundamentally with regard to their applicability in dedusting systems. The long-term stability of both the electronic and optical components of the sensors has not yet been investigated under the focus of emission characterization.

In this contribution, the aging behavior of low-cost PM sensors under idealized conditions (flow form, particle concentration levels, relative humidity), is presented in relation to the particle deposition inside the sensor...

Air filter clogging causes an increase in energy consumption, albeit still lower than that required for heating or air conditioning, since the fans speed may be increased to keep a constant air flow. Nevertheless, taking into account the working time of fan in various buildings such as commercial center, hospital…, this overconsumption can be significant. To avoid this over-consumption, one can either replace the filters more frequently or monitor the filter pressure drop to avoid unnecessary maintenance. Ultra-low energy monitoring system will thus help significantly reduce the fans power consumption [1,2] and improve the maintenance of central air handling units.

The aim of this work is to develop a filter clogging monitoring system by measuring the difference between upstream and downstream pressures of the filter. The energy supply and communication system of the connected filter will be wireless for ease of maintenance...

Replacing fossil fuels for heat and power generation by biomass combustion processes is a main topic and challenge during the coming years. By increasing the number of biomass heating systems without additional gas cleaning high dust load of the ambient air will be created. Straw, a role jutting out befit the energetic use of biomass, is included at this. For a utilization of this considerable potential however technical measures are necessary.

In case of this German government has given a new law for emissions. Stage 2 of this policy is valid until 2015 and restricts the emission value for dust down to 20 mg/m³. Important for the function of furnace is a low resistance of filtration system. Aerosols from wood and biomass- firing have a special behaviour. If the surface energy of filtration material is correlating to the loading of dust the separation efficiency increasing from 20 to 90 %. In addition, agglomeration effects are important for separation effect along the fibre structure.

Nonwoven fabric made by a composition between a coarse layer and a fine layer are able to separate the ultrafine dust from the gas stream. The key issue is the connection with water- jet between the fine and the coarse layer. But also the fibre material is important for the separation effect.

The high filtration efficiency for the biomass fly ash can’t be declared only because of mechanical effects. Surface effects and electrical potential have to be included. It was found that...

The difference in efficiency results in filter and filter media testing is often based on the difference in measuring technology. Scattered light particle sizers or SMPS systems usually used in fractional efficiency testing vs. the integral efficiency obtained by a scattered light photometer.

Various standards define different test instrumentation to measure the efficiency of various filters and filter materials for different applications.

Commonly used is either the efficiency by particle size as e.g.by ISO 11155-1 and DIN EN 71460 -1+3 in Cabin air filtration, ISO 29463 in HEPA/ULPA filtration, ISO 16890 in general ventilation filtration testing, or the integral efficiency with a defined test aerosol as by EN 149, EN 143, 42 CFR 84, and GB 2626 in mask testing, DIN EN/IEC 60335-2-69 A.3/AA.22.201.2 or DIN IEC 60312 in vacuum cleaner filter testing.

In the PMFT Series by Palas® the aerosol spectrometer Promo® was successfully integrated to measure integral efficiency with comparable results to the photometer as described in the mask testing standards. Based on the measurement of efficiency by particle size, the system can adjust the particle size distribution to the requirements of the different standards. This is necessary to get comparable results with the photometer method.

Additional advantage by using the particle counting device is for sure to obtain efficiency by particle size also. The system can be adjusted to different test conditions concerning particle concentration and air flow of filter media testing according to the standards for cabin air filters, general ventilation filters and to some extend even HEPA filters.

This presentation outlines the technical background to convert the data from the Promo® Aerosol spectrometer in comparable results with photometer-based measurements. The results from round robin tests for face masks in Europe and United States prove...

Due to the still ongoing Coronavirus (COVID-19) pandemic the process of virus transmission and infection prevention are the subject of several research studies. It is well known, that infectious particles such as viruses or bacteria can be transmitted via surfaces or directly via air from human to human. This mechanism depends on the virus species and the surface material but also on environmental conditions such as temperature or relative humidity (Whitworth et al, 2020). The behaviour and stability of viral particles on surfaces and in air can play a significant role when implementing viruses into air filtration processes (Verreault et al, 2015).

As air filters, air cleaning devices or protection masks are usually tested under laboratory conditions using predominantly non-biological aerosols such as DEHS, salt particles or tobacco smoke, it is important to also generate knowledge about the behaviour of viruses. Therefore, as a first step two surrogate viruses were chosen for further investigation of their stability on four different surfaces at three temperatures over a defined period of time (three months). MS2 bacteriophage, a well-known bacterial virus, was chosen as representative for a robust non-enveloped virus, whereas phi6 bacteriophage was selected as an enveloped virus posing as a surrogate for Ebola virus or Coronavirus. In a second step, both viral surrogates were meant to be used as aerosol for testing air filters within a filter test rig. While establishing this process, factors such as sampling stress by the aerosol generator or stable distribution within the air stream were considered. The aim was to compare the two viruses within the different setups in order to establish a stable test aerosol containing MS2 or phi6 bacteriophages...

The performance and operation of vehicles mainly depend on clean air supply to the IC engines. Air filters are necessary for providing clean air to the engines. A good air filter supports the engine operation by ensuring that the air entering the system is clean and free of grit and dust. Fibre diameter and pore size are critical parameters that significantly affect the air filter media’s filtration performance and dust deposition. Nanofibers are typically fibres with less than 1 μm, and the nanofiber-coated filter media offers higher filtration performance than the conventional filters. The addition of nanofibers also extends the life of the filter by making it easier to clean because the fibres keep the particulate at the surface rather than depth loading. In this study, Nylon nanofibers were coated over a cellulose based conventional filter media using an electrospinning process. The coated media’s performance was evaluated in terms of filtration efficiency, quality factor (Q-factor), etc. The filtration test was performed on a lab-scale air filtration test apparatus and compared to the conventional filter media. The addition of Nylon nanofibers on the surface of the conventional media showed...

One of the main design goals for filter media is a high separation performance while pressure drop is low. During manufacturing processes such as pleating filter media or during operation, the nonwoven material is compacted locally which is of importance for the mentioned quality characteristics, because the compaction leads to a local variation of the fiber volume fraction and therefore, to a non-uniform distribution of flow resistance and filtration performance.

In this work, the influence of compression on the performance of flat filter media is examined both for “classical” materials using mechanical deposition and electret media. Two different fibrous media made of polypropylene (PP, see Figure 1) investigated whereby one is electrically charged. After the characterization of both media by the thickness, basis weight and airflow for a given pressure drop, properties like the solid volume fraction and flow resistivity can be deduced...

Air pollution, due to high concentrations of fine/ultrafine particles, was ranked as the leading cause of death in the world, in a recent report by the State of Global Air (2008). The efficient fiber filtration process, for this fine particle separation, encounters great difficulties of clogging due to a significant increase in pressure drop resulting from the higher specific surface area of particles. To delay the onset of clogging, the surface area of fiber filters is increased through the pleating process. However, this method of manufacturing may generate local Solid Volume Fraction (SVF) heterogeneities. This filter characteristic being the critical parameter affecting the filter performance, it is essential to know the impacts of such modifications on the permeability and the efficiency of a filter.
To study the impact of solid volume fraction heterogeneties on the performance of filters, the filter structure needs to be perfectly characterized but available experimental techniques only allow access to very macroscopic information. Hence, for this purpose, the CFD approach was adopted in the present study to perform a detailed numerical study using the software, GeoDict...

Choosing the right air filtration system can be a difficult decision, and even with manufacturer information to hand, it can be hard to assess long-term efficiency in tricky filtration applications. Of course, this also assumes that there are no discrepancies between the documentation and product you receive.

EUROVENT is an umbrella association which sets out to ensure that indoor climate (HVAC), process cooling, food cold chain, and industrial ventilation industries provide complete transparency and security to customers, but what does a EUROVENT certification mean?

One of the numerous misconceptions of EUROVENT is, that EUROVENT in many ways resembles an industrial trust that ensures market dominance of a selected number of companies in the ventilation industry. This notion includes the operates via multilateral distribution agreements, for instance. Instead, EUROVENT an umbrella organisation of European industrial associations and its dominating entrepreneurial principles is the full respect of European anti-trust laws.

EUROVENT is headed by a Commission whose members are delegates from 17 participating European industrial associations. The EUROVENT Commission sets strategic objectives for the entire EUROVENT organization and to emphasize its democratic foundations all 17 members of the EUROVENT Commission have equal voting rights, regardless of their own number of members or the gross financial turnover of their national members.

Product groups are installed by the EUROVENT Commission to focus on different subsectors of the ventilation industry and aim to provide technical recommendations to legislative supranational bodies....

processes of particle structures. Either the collectors, the particles or both can be magnetized. Magnetic separation between particle structures and collectors is already well established in the field of solid-liquid separation and also allows separation of particles in the lower submicron size range on an industrial scale (Ladislav 2001; Svarovsky 2000).

The use of magnetic effects, such as magnetic-induced motion excitation for the regeneration of individual filter fibers (in the field of depth filtration) or entire filter media (in the field of surface filtration), could also find application in the field of gas-particle separation technology. However, there are no studies in literature dealing with the separation of non-magnetizable particle structures from ferromagnetic fibers by exploiting magnetic effects. The detachment of non-magnetizable particle structures depends on the structural build-up of the particle layer to be detached and the loading of the fiber (Löffler 1972; Müller 2017). Therefore, knowledge of the morphology of the particle layer and the total load is of high significance. It is expected that the different morphology of particle structures will also result in differences in the detachment behavior.

For the fundamental investigation of the novel regeneration concept by magnetic forces, the detachment of non-magnetic particle agglomerates will be performed using a single ferromagnetic fiber (Figure 1). The fiber is fixed on one side and is magnetized and deflected by the application of an external magnetic field (Helmholtz coils). If the inertial forces acting on the particle agglomerates due to the acceleration of the fiber are greater than the adhesive forces, the agglomerates detach from the fiber.

The presented work aims to introduce the novel concept of magnetic-induced cleaning and to present first findings on magnetic-induced particle detachment...

Electrical charges in fibrous filter media can lead to non-monotonic penetration curves because the dominant effect of filtration changes over time. The two orange curves in Figure 1 show how the penetration is low at the beginning of the experiment, then increases and finally decreases again. At first, the charges are so high that most particles get trapped. Over time, as more mass deposits, the charges weaken, and fewer particles are trapped. Later still, as enough mass was deposited, captured particles contribute increasingly to the capture efficiency and more particles are trapped again.

Our earlier attempts to simulate this behavior could not reproduce this behavior, as illustrated by the simulation results on the left of Figure 1. They were not taking decreasing charges into account. By making the electrical charges depend on the deposited dust, the digital filtration experiments reproduce the general behavior of the physical experiments as illustrated on the right of Figure 1.

As there are many unknowns regarding how exactly the charge reduction depends on the deposited mass, we developed and present a general modeling framework that allows the detailed modelling of electrical charges, both depending on the deposited mass but also on properties of individual fibers, in order to improve the agreement of digital filter experiments with physical filter experiments...

Simulation of fluid flow and particle deposition with 3D computer models of the pore structure of filter media is a tool for rapid cost-efficient layout of filter media for industrial filter applications, and moreover for improvement of the scientific understanding of filter processes and the involved material systems.

To obtain reliable simulation results which reproduce the real behavior precisely, the simulation must be validated under well-defined laboratory conditions. The validation usually consists of the comparison of pressure drops, filtration efficiencies, deposited particle masses and/or filter cake heights. If the comparison of simulation and measurement results shows considerable deviations, the physical models and numerical implementation of the simulation must be revised, and also measurement errors must be considered.
The aim of this work is to validate the simulation of continuous aerosol deposition at wire meshes, where non-trivial adhesion forces occur between particles and particles and between particles and wires, with it4e’s simulation software DNSlab^®...

Filtration solutions and dedusting systems make a significant contribution to safe production in the company. In this context, it is important to be able to meet the individual requirements of the process and the associated filtration technology. Innovation and development are the driving force in today's globally networked world. Especially in processes with high temperatures it is important to concentrate on the core tasks, namely the permanent further development of the process as well as the focus on pure productivity. Therefore, a filtration system needs to set new standards....Examples include various applications like dryers, biomass combustion plants, rotary kilns, glass tank dedusting and high-temperature filtration downstream of mill systems and so on....

SMF^® modules are proven for a very large number of exhaust gas filtration applications used by vehicle manufacturers for applications that are subject to the current European emission legislation and thus strict requirements for particle number reduction. More than 2 million m² of HJS Sintered Metal Filter (SMF^®) material have been produced for these applications within the last 15 years, with a peak production of 300.000 m² p.a..

In order to qualify the SMF material for industrial filtration processes and to describe the performance of the current filter medium measurements according to the corresponding standards of both oil filtration, e.g. Mulitpass acc. ISO 16889 and testing regulations for air filters as ISO 5011, VDI 3926 and ISO 16890 have been carried out. There are first applications in the industrial filtration of gases, in which in addition to the thermal robustness of the filter material, the high retention capacity and good cleanability of inert filtrate are key factors.

Following the qualification of the SMF material for hydraulic filtration applications and APC, the first promising applications are now emerging in the field of hot gas dedusting. Filter elements are produced in prototype manufacturing processes for the first tests that go beyond material tests. Filter cartridges with ø 130 mm, 160 mm and 325 mm up to 3 m in length are currently being tested and further developed for hot gas filtration to enable lengths of up to approx. 9 m. Tests have shown...

Electrostatic precipitators and fibrous filters are the most commonly used gas cleaning devices for the removal of particulate matter in power plants and industries. However, the collection efficiency of electrostatic precipitators decreases for particles smaller than 1 μm. Fibrous filters provide higher filtration efficiency for particles of this size, but the pressure drop is higher, and additional energy is needed to supply the outlet fan. Recently, special attention from engineers has been given to hybrid constructions, which apply electrostatic fields and forces in order to improve the performance of bag filters. However, to date, ESP-assisted fabric filter has limited use because of the increased complexity of the system, larger size, filter media may be easily damaged by sparks, and replacing filter bag may be difficult due to the existence of extra parts such as electrodes in complex design, or cost reason may exist due to the additional parts.

The present work proposes simplifying the construction of an electrostatic-assisted fabric filter system by using a pre-charger for efficient control of industrial air pollution. In view of the above, the current paper is aimed at studying the pulse jet filtration behavior assisted with a pre-charger using fly ash aerosol...

Several health effects are associated with the air quality and the presence of indoor generated pollutants, including NOx, volatile organic compounds (VOCs), formaldehyde, gases generated from cleaning products, etc. Considering that the world´s population generally spends 90% of their time indoors, it is highly important to eliminate indoor pollutants and particles. For this reason, the addition of gas filtration media in indoor purifiers is considerably increasing. All these pollutants can be removed with a media blend consisting of activated carbon and permanganate-based media.

The minimization of dust release from pellets is especially necessary for indoor air quality equipment in order to reduce the blockage rate of particle filters and increase the frequency of change of these particle filters. This implies a decrease in cost due to maintenance or replacement of particle filters. Higher dust generation will also increase the pressure drop, increasing the energy consumption and the operation cost. The minimization of the dust generated from the pellets is a must. The hardness is another important factor to consider for the assembly process of the filters containing the media, especially for automatic filling systems, since low hardness can cause issues and dust generation during the filling process of the filters.

The increase in hardness, decrease in dust and improvement of other mechanical parameters need to be adjusted to obtain a filtration product that complies with the operation conditions without clogging the particle filters. The most important development challenge of such robust product relies on the adsorption capacity, which is often significantly sacrificed to obtain better mechanical properties. Most of the already commercialized permanganate-based spheres, which show strong mechanical properties, present a sharp decrease in capacity of up to 70% compared to standard permanganate spheres with average mechanical properties and dust release.

This work presents the development of a novel formula with both strong mechanical properties, low dust generation and high adsorption capacity. Several laboratory and industrial tests have been done to demonstrate...

Process managers, consumers, and automobile operators are increasingly aware that airborne molecular contaminants (AMC) are problematic to production yields and the air we breathe in cars and buildings. Since these airborne contaminants are molecular in size, sorbent technologies must correctly match both the size of the molecules and the concentration levels inherent to the application conditions.

We will demonstrate by presentation of data that corresponds to specific application conditions how small mesh granular activated carbon (GAC) can be formatted in

non-woven structures to efficiently capture molecular contaminants. Adsorption data will be shared illustrating the removal of common gases such as VOC's, NHC, SOx, NOx, and aldehydes. These data will be correlated to flow conditions that match such applications as room air cleaners, HVAC systems, and fuel cell filters.

Finally, we will exhibit composite non-woven structures designed to serve dual purposes. This includes the layering of sorbent structures impregnated for different purposes; as well as sorbent media that is laminated to media designed for particulate removal. This segment demonstrates multi-layer composite design that can optimize system design within a smaller footprint...

The promotion of e-mobility and the need of energy storage leads to a high demand for corresponding battery solutions in many industrialized countries. The production of batteries is therefore the focus of many development activities.

In the production of lithium-ion batteries, a key industry in the energy transition with enormous growth potential, such production areas are the process steps "trimming" to "electrolyte filling". To keep a high battery performance the handling of lithium-containing materials requires a very clean and dry environment with dew points well below -40°C. To ensure an economic production the dry air have to be recirculated including a high efficiency filtration. The laser cutting process is ideal for sizing the electrodes, but this also produces large quantities of ultra-fine particles and an amount of trace gases.

These trace gases obviously include components that causes damages at the air drying system and could influence the product quality.

So it is part of a currently ILK research project to find suitable solutions to separate these components in an economic way. The project will

• determine main trace components that causes or could causes damages at the production line and/or the product,
• find suitable sorption technologies able to reduce them and
• build up an air cleaning prototype to verify the function also in real production environmental.

In the presentation first results of this project will be discussed...

Vapors from industrial processes such as rubber vulcanization are contaminants. Manufacturers of rubber goods must remove them from the fumes to obey maximum allowable emissions limits set by environmental protection agencies. Other processes, e.g., coffee roasting, release significant amounts of vapors that may have a commercial value into the atmosphere. These contaminants tend to condense in the smoke evacuation systems, implying an economic loss due to maintenance and machinery repositioning. In both cases, it is desirable to capture those vapors effectively, turning them into a resource whenever possible.

Examples of technologies suitable for removing vapors from the air are thermal oxidation, activated carbon adsorption, and wet scrubbers. However, those technologies require frequent maintenance and high operational costs.

We present some experimental results with a prototype built to demonstrate new patented technology to remove vapors from the air. The idea is to force the vapor condensation into tiny droplets and separate them using a high-efficiency cyclone...

Fibrous coalescence filters consisting of micro glass fibers and sometimes small amounts of synthetic fibers are widely applied in gas cleaning processes to separate liquid droplets from a gas flow (e.g. oil mists). When separated on the fibers of the filter media, the deposited oil can take different shapes dependent on the oil saturation, wettability, roughness and diameter of the fibers and fiber arrangement (e.g. axisymmetric barrel-shaped droplets, axially asymmetric clam-shell droplets or oil sails between adjacent fibers). To understand the initial state of the coalescence filtration process as well as the impact of the deposited oil structures within the filter matrix on the separation efficiency, it is essential to characterize these deposited oil structures. Using X-Ray microtomography (µ-CT) and an artificial intelligence tool for segmentation, deposited oil structures can be visualized, identified and analyzed down to sizes in the micrometer region. The main emphasis of this work is to quantify and compare oil structures formed at three different filtration velocities at a defined oil saturation of the coalescence filter media by a µ-CT...

Screw compressors are widely used to provide compressed air for a variety of processes. These compressors are predominantly oil-lubricated and disperse oil as oil mist into the compressed air. This dispersed oil needs to be separated in a following step to minimize oil consumption by recirculating the separated oil and to prevent problems further downstream. Therefore, oil-lubricated screw compressors are equipped with downstream separators, consisting of a centrifugal separator and a coalescence filter. The operating conditions at these coalescers are typically 70 to 100 °C and 5 to 13 bar. The dispersed oil mass that needs to be separated is five to ten times the mass of the compressed air. Unfortunately, most of the published literature characterizing the filter media in terms of differential pressure and filter efficiency is on research at atmospheric pressure, at room temperature, and using concentrations far below the typical values.

This project aimed to close the knowledge gap of oil mist characteristics and filter efficiencies at realistic conditions by making inline measurements of particle size distributions in raw and clean gas of oil-lubricated screw compressors at operating conditions possible...

Continuous operation of a compact dust collector with a pleated filter, which is widely used, requires the removal of collected dust particles accumulated on the filter surface and inside. The pulse-jet cleaning method is commonly used. However, since dust particles cannot be completely removed and some of them remain, the performance of the dust collector, such as pressure drop, effective filtration area etc., changes with operation time. The objective of this study is to investigate the influence of pulse-jet pressure on these performances and to analyze the accumulation behavior of dust particles on and inside the filter...

The steel industry is responsible for a large number of pollutants that need to be treated before being released into the atmosphere, such as particulate materials. To clean the particulate materials, the dirty gas passes through a bag filter that is a gas-solid filtration equipment with high collection efficiency for a wide particle size range, low cost and easy operation. A pre-treatment used in the filter bags to increase the collection efficiency is the precoating which aims to reduce or prevent the saturation of the bags. Precoating consists of covering the inside and the surface of non-woven filter media with particulate material forming an initial dust layer that acts as a filtering element with surface filtration as the collection mechanism. In addition to ensuring that the air flow passes freely through the bag, improving the performance of the filter medium while extending its useful life. Precoating is studied in a bag filter to remove particulate matter, however, there are not many studies on precoating in a bag filter in relation to industry, especially steel industry. Observing the deficiency in the literature on the subject, this work aims to evaluate the precoating efficiency in the particulate matter collection in the steel industry...

Particulate matter suspended in the air is a health hazard and it can cause a number of serious respiratory illnesses. In addition, microorganisms such as viruses, bacteria and fungi are also classified as particulate matter, more specifically, bioaerosols, and it can be inhaled by humans causing diseases such as: Influenza, tuberculosis and covid-19. To reatin particulate materials, electrospun filters are used due to their high surface area and good ability to capture airborne particles. In addition, this material allows the incorporation of nanoparticles in its fibers that improve filtration performance, some of which have a biocidal effect. In this context, this work aims at the production of a filter medium produced from dissolved dimethylformamide (DMF) polyacrylonitrile, with zinc oxide nanoparticles incorporated into the solution...

The ideal depth filter media aims for the highest possible degree of separation, with the lowest possible aerodynamic resistance of the fluid flowing through the medium and maximal particle loading capacity. The overall goal of this study is the development of an efficient filtration submodel, predicting collection efficiency and filter pressure drop of fibrous filter media over time, derived from data generated by detailed fully- resolved simulations at the micron- and submicron-scale for Arizona Dust. In this context, the current work investigates particle deposition on a single fiber collector using three-dimensional, fully resolved simulations based on a coupled Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) approach. In this approach the fluid field around each particle is accurately resolved through an immersed-boundary method and, consequently, the aerodynamic forces acting on each particle are accurately predicted after integrating the surface stresses and pressure along the particle surface. Contacts between two particles or particle and fiber are resolved directly by the DEM algorithm. Vital contact model parameters for the DEM simulation, e.g. coefficient of restitution, rolling- and sliding friction coefficients and adhesion- cohesion parameters, are calibrated upfront using a bulk calibration approach. Here, bulk material properties are measured from suitable experiments and used to calibrate relevant model parameters in virtual-twin simulations of said experiments. Based on the sizes of particles and fibers, the current work is divided into two parts. The first part considers the deposition of micron-sized particles on a micron- sized fiber, whereas the second part simulates the deposition of sub-micron-sized particles on a nanofiber. For the latter effort, slip flow around the fiber and Brownian motion of the particles is included. The presented model allows for an accurate description of the behavior of aerosol particles dispersed...

Due to the COVID-19 pandemic, the adjustment of air supply parameters is an important issue in terms of reducing the risk of indoor airborne infection. This is often done without considering energy efficiency or thermal comfort (Srivastava, 2021; Kurnitski, 2021). The risk of infection in existing HVAC systems has already been investigated in the past. There are extensive publications of experimental and simulative studies (Motamedi, 2022; Tobisch, 2021). In addition, recommendations for HVAC have been made using several models (Liu, 2021; Pathak, 2021). However, the studies are related to a specific space or rather to a regulation instead of a prediction and adapted control.

This work aims to predict and control an indoor HVAC system, e.g. in a classroom or in a public transport vehicle, and to adapt it in an energy-efficient and health-oriented manner using an artificial intelligence...

Since 2018, air filters for general ventilation have to be classified and the performance parameters pressure drop and fractional efficiency determined in accordance with ISO 16890. The introduction of this guideline also has an impact on regulations that (still) refer to filter classes according to EN 779. For example, there are different recommendations at national (VDI 6022) and international (Eurovent 4/23) levels for the selection of those air filters depending on the outside air quality and type of use of the building in order to achieve the required supply air quality. The achieved supply air qualities and in particular the achieved indoor air quality in practice when using the recommended filter types have not been published yet. These questions are being investigated in a current research project (IGF 21330 N)...

In the light of the growing awareness of air pollution and the COVID-19 pandemic, the need for improving the indoor air quality and reducing the transmission of airborne infections is steadily increasing. Air cleaners have a great potential for beneficially contributing to these aims by filtration of airborne particles. So far, most air cleaners utilize electret filters, which combine a high filtration efficiency with a low pressure drop. However, electret filters lose their non-regenerative charge over time, which reduces the filtration efficiency with increasing service life. On the other hand, there are electrostatic precipitators (ESP), which are resource saving as their collection plates can be washed, but the generation of ions by corona discharging is often accompanied by the emission of ozone. The goal of the project PureAir is to develop a filtration solution that combines the high filtration efficiency without ozone production of electret filters with the long-term stability and washability of ESP. The goal shall be achieved with...

Filters used in heating, ventilation and air-conditioning (HVAC) systems are categorised by ISO 16890 depending on the fractional efficiency for aerosol removal during testing measured using an Optical Particle Counter (OPC). ePM1 results are reported for DiEthylHexylSebacate (DEHS) particles with particle diameters of 0.3 µm – 1 µm. Higher efficiency filters (such as those intended for hospitals and clean room environments) are categorised by ISO 29463 based on the most penetrating particle size determined in the range 0.04 µm – 1 µm using monodisperse or polydisperse test aerosols and a Condensation Particle Counter (CPC) to detect the smallest particles. This submicron particle size range is of major public concern due to potential penetration through the respiratory system and negative effects on human health.

An ideal instrument for detailed characterisation of air filter media is the Aerodynamic Aerosol Classifier (AAC), which offers substantially higher particle transmission efficiency than electrical mobility techniques and elimination of multiple charging issues (Payne et al. 2018). The AAC selects truly monodisperse liquid or solid particles without charging from 0.025 µm to >5 µm, by passing aerosol between rotating concentric cylinders with a coaxial sheath flow. In conjunction with a CPC, the AAC can also conduct high resolution scans of polydisperse particle size distributions in aerodynamic space, which is the most relevant metric for aerosol flow through filters and particle capture by interception or impaction.

In this study the filtration properties of commercial air filter media adhering to different categories in ISO standards 16890 and 29463 were evaluated in detail. Polydisperse DEHS particle size distributions up-and downstream of the filter samples were recorded over a broad size range, using a continuous scanning AAC procedure (Payne et al. 2019)....

The air filters fabrics made up of polypropylene plastic were coated with novel anti- microbial electroless plating technology of electroless copper to neutralize bacteria and viruses on contact as the air passes over the mesh. The treated filters were fitted in the air conditioners and air samples from different locations, before and after switching on the device with filters were collected. The microbiological analysis of active air sampling as the air passes over the mesh was done and the total Plate Count (TPC), which detects and quantitates total bacterial concentration in the sample after 24 h of incubation and Yeast and Mold Counts (YMC) used to detect and quantify the amount of fungal growth, was recorded as under. Air samples collected with Sample 1 filters showed...

Copper oxide (CuO) nanoparticles functionalised using amino acids, were prepared and formulated into an effective antipathogenic ink. Following successful incorporation of the developed ink into disposable face masks for the prevention of respiratory infections, we demonstrate here the successful development and incorpration of the CuO nanoparticle ink into HVAC filter media. The nano ink was applied and cured on polyester and polypropelyne HVAC filtration material and evaluated for antiviral and antipathogenic performance. At least a 90% reduction was found in influenza and SARSCoV2 viruses after 2 hours treatment and at least 99% reduction was found in Pseudomonas aeruginosa Acinetobacter buamannii and Escherichia coli after 18 hours treatment.

The medicinal properties of copper has been well established and have been used since the time of the Egyptian empire. Current uses of copper include hospital touch surfaces e.g. bed frames and door handles, due to copper oxide having unique electrical properties allowing biomedical and antipathogenic properties. Copper nanoparticles were used during both the Swine flu and Bird flu outbreaks and, more recently, have been used to combat the SARSCoV-19 pandemic. Herein we report an optimised synthesis of copper nanoparticles and their functionalisation of filtration devices, including the antiviral and antimicrobial properties...

University and Schools are the most used social infrastructures, the first place for social activity and the most important indoor environment for students besides the home.

The COVID-19 pandemic has demonstrated the need for strategies to control the spread of airborne respiratory pathogens and whether HVAC filtering systems (including maintenance plans) are enough to guarantee good indoor air quality. This has brought an increasing demand for innovating filtering systems for novel technologies to prioritize clean air: Controlling the presence of biological pollutants must take in the countless sources of these pollutants, as the HVAC system itself, the recirculation rate of exhausted air, the continuous emission of microorganism by the occupants and pollutions entrance from outside areas.

The first aim of this paper has been to monitor the bacteria and fungi air concentration air by traditional microbiological techniques like counting the grown cultures on Petri dishes on air treated using microflow instruments and evaluating the efficacy of Crossfield filtering technologies in antimicrobial activity against bacteria, fungi, and viruses where the HVAC system already treats the air in university classroom during lessons.

The main objective of this test campaign will be to investigate the presence of Antibiotic-resistant pathogens in bacteria culture collected during this pilot campaign and their inactivation using Crossfield technology:

Antibiotic-resistant pathogens pose a significant threat to human health. Several dispersal mechanisms have been described, but the transport of microbes and antibiotic-resistance genes via atmospheric particles has received little attention as a pathway for global dissemination.

To reach the goal we will apply culture independent techniques based on next generation sequences to detect microorganisms’ nucleic acid in parallel to traditional microbiological technique.

Due to the flexible applicability and easy handling, mobile dust collection systems with cleanable filters are often used to reduce high particle loads at changing workplaces and to remove particles from the room air. Most mobile dust collectors use the established method of differential pressure-controlled pulse jet filter cleaning to unload and extend the life of the filter cartridges. The performance of dust collection systems depends on many factors: the filter element used, dust and carrier gas properties, operating method, and time. The size and design are primarily based on the extraction volume flow and dust concentration. Dust collectors from different manufacturers thus differ in their collection performance due to their design. The objective is to define a testing procedure to evaluate in advance and compare the performance of dust collection systems with integrated fan and cleanable filters after a long period of usage among different manufacturers. Performance data such as system pressure drop, gas flow rate, system energy consumption, and particulate emission from the system after accelerated aging are to be determined...

Urban Greenings represent high-performance instruments dealing the consequences of the climate change. They provide shade, cool the air by evaporation and ensure the vital gas exchange concerning oxygen, carbon dioxide and nitrogen oxide. After all, the plants separate harmful fine dust as well.

Measuring the overall performance of these greenings is possible comparing the values of the parameters on the luv- and on the lee-side using high-performance measuring devices. Due to the dependence on the wind direction those investigations are very time- and cost-consuming.

The project´s core is therefore the development of a fully-automatic system using a higher number of low-cost sensors for fine dust, gaseous components and temperature. Combined with meteorological measurements like wind-speed and

-direction and communication via Long Range Wide Area Network (LoRaWAN) the system enables the identification of the relevant pair of sensors balancing the performance of urban greenings...

This contribution presents a new on-line method for measuring trace gas concentrations for pursuing gas emissions which are released from filters.

The method based primarily on the photoacoustic (PA-) effect. In the underlying PA-effect light is first absorbed by molecules and the absorbed energy is then converted into sound via intermolecular energy transfer processes. The generated sound can then easily be detected by a microphone. The experimental setup only needs a pulsed light source, a sound detector and a measuring cell as basic components. For measuring traces of hydrocarbons the setup was...

Particle filtering face masks are designed to protect against (droplet) infection with COVID-19. The viruses that settle in the respiratory tract of an infected person become airborne through fine infectious droplets when sneezing, coughing or speaking, but also when breathing itself, and can thus be inhaled by other people.

The use of conventional microfiber filter media for face masks would be limiting in terms of the filtration performance and protective effect. Due to the mechanical filtration mechanisms, such filter media typically have a filtration minimum for particles in the range around 0.3 μm (Most Penetrating Particle Size), which is also where the infectious droplets and viruses are. This filtration minimum can be compensated by electrostatic fiber charging. Face masks made of such electret filters can be used to filter both infectious droplets and viruses. Consequently, the spread of aerosolized viruses can be contained by wearing face masks.

Unfortunately, research to date has not provided any reliable findings on the influences of real-life wearing conditions, such as wetting of the filter media by droplets from the breathing air and mechanical deformation under alternating flow directions (inhalation and exhalation) on the flow/breathing resistance of the face masks. Local airflow dynamics through the filter media and leaky zones in the contact of the face masks with the face are are also poorly studied. Thus, there is a possibility of becoming infected with the SARS-CoV-2 virus despite wearing a tested face mask. To minimize or eliminate the infection risk, masks have been studied with the aim of optimization.

Crucial is here the transfer of real-life wearing conditions into lab studies. For this purpose, wearing was mimicked using a Sheffield test head with a face mask on. A microtomography (µCT) was used to scan the 3D fir in detail. The resulting scans are shown...

Today, cabin air filters are part of the basic equipment of passenger cars. In addition to the highest possible filtration efficiency for particles and, in the case of combination filters with an activated carbon layer, for harmful gases, the filters must also have a low pressure drop. Another requirement is that the filters fit into the limited installation volume, which usually has a small installation cross-section. Automotive cabin air filters are offered as pleated filters to increase the filter media surface and thus reduce the effective face velocity, resulting in a lower pressure drop.

In the project "Test method for characterizing multi-effect filters for indoor air as a basis for realistic performance assessment", one aspect investigated was the extent to which the relationships between filter media structure (fiber layers and incorporated sorbents), filter geometry (number and depth of pleats), pressure drop and separation efficiency for particles and gaseous contaminants can be described with the aid of CFD simulations.

For this purpose, the pressure differences were determined as experimental tests on both prefabricated automotive cabin filters and the filter media used in them. In addition, tests were carried out to determine the particle fractional collection efficiency as well as breakthrough tests to determine the adsorption capacity. The results were...

Cabin air filters are part of standard equipment in modern vehicles and protect users in a car cabin from exposure to a variety of contaminants. The presence of fine dust particles in air can cause serious adverse health problems on passengers in car. Despite the various advantages of micro-sized fibrous air filters in the automobile cabin today, more functional improvements are required because they cannot capture ultra-fine dust particles. In order to solve these problems, this study have developed automobile cabin air filter media with nano-sized fibers using nanotechnology.

"Nano" technically refers to physical quantities within the scale of a billionth of the reference unit and nanofibers are the fibers with diameters in the nanometer range. Nanofibers are produced in the form of spider web like structures [1]. Because of easy usage and ability to fabricate nanofibers, electrospinning is one of the most commonly used method [2]. Nanofiber media have low weight, high air permeability and small pore size that make them suitable for various filtration applications, particularly for smaller particles [3-4].

Nanofiber webs formed by nanofibers are able to capture very small particles with their small pores and provide low pressure drop due to their high porosity. By adjusting the amount of nanofiber on the filtration material, the target particles in smaller size can be kept at the desired fractional efficiency levels and the air can be cleaned at the desired rate.

In this study cabin air nanofiber filter media for automotive compared to conventional filter media has been designed to offer the highest protection against fine particles and microorganisms, optimizing the pressure drop and the efficiency of the filter. The capabilities of nanofibers will be explored cabin air filter media performance data. Scanning electron microscope (SEM) and Porometer were used for fiber characterization, and finally, efficiency test were conducted to evaluate the filter performance of developed nanofiber based and traditioanal spunbond air filter. The results showed that...

Gas adsorption layers for air filtration were fabricated by wet-laid nonwoven process using activated carbon fibers. Considering the wetting effect of ACF during the wet-laid process, the optimal content of ACF was 0.2g/100cm². The gas removal capacity was not hindered by the blending of the PET binders. The tensile strength, stiffness, and the dimensional stability of the ACF nonwoven could be adjusted by the amount and composition of the binders. With the increase of low-melting PET binder, the mechanical strength was improved but shrinkage during the bonding procedure increased.

The effect of binders on the particulate filtration performances were also evaluated. Binder content and blend ratio had an effect on PFE and air flow resistance, respectively. The ACF nonwoven showed...

The cyclone separator is an essential mechanical gas-solid separation equipment, widely used in the pharmaceutical, metallurgical and petrochemical industries. Vortex plays a significant role in the cyclone fluid motion but an insufficient understanding of this underpinning operating mechanism has plagued the performance and expansion of the cyclone technology, leaving the device penchant for several reliability challenges. This study thus aims to numerically investigate the dynamic characteristics and periodic motion of vortex core in the cyclone...

A cyclone is a common piece of equipment that has been used in industry since the 1800s to separate pollutants from gas streams. Although the geometry is simple, the flow in a cyclone is complex, due to the highly turbulent transient three-dimensional nature of the flow. It can therefore be challenging to achieve an accurate estimation of the pressure and velocity field using computational fluid dynamics (CFD). Besides the influence of the geometry and turbulence model, the selected numerical interpolation schemes affect the results of the CFD simulation. The aim of this paper is to provide an overview of the influence of the various numerical interpolation schemes available in Ansys Fluent 2021 R1 on the calculated pressure and velocity field in a Stairmand High-Efficiency cyclone. The CFD results are compared with experimental data obtained by Hoekstra using laser Doppler anemometry (LDA).

Ansys Fluent offers multiple pressure interpolation techniques, where the PRESTO! and body force weighted (BFW) are recommended by Ansys for (axisymmetric) swirling flows. These two pressure interpolation schemes are varied with the available spatial interpolation schemes, including higher-order interpolation schemes for the Reynolds stress term. The interpolation schemes available are first-order upwind (FOU), second-order upwind (SOU), QUICK, and MUSCL, where the latter three are higher-order schemes.

The BFW pressure interpolation scheme significantly underestimates the pressure loss in the cyclone. This deviation in pressure loss can be reduced by using a higher-order interpolation scheme for the Reynolds stress term. However, the deviation is higher than the experimental error for all combinations using the BFW interpolation scheme. For the PRESTO! pressure interpolation scheme, the difference in pressure loss falls within...

Due to their potential and remarkable promises, nanomaterial’s market has considerably increased during the last two decades and it is expected to grow even more in the coming years. This leads to the presence of engineered nanoparticles (ENP) in waste discharges. To date, there is no global strategy for handling waste containing ENP (called nano-waste), therefore it is treated with no specific standard. Thermal treatment is usually preferred as management strategy for nano-waste, although recent studies have shown that, when incinerated, part of its ENP can be released as an aerosol into the flue gas [1-2]. A combination of flue gas cleaning systems is used in Waste Incineration Plants (WIP) to reduce the release of pollutants into the environment. Electrostatic precipitators (ESP) and bag filters are typically used for fine particle removal, while wet scrubbers are employed for acid gases cleaning. Depending on the operating and design conditions, interesting particle collection efficiencies can be achieved by spray scrubbers [3]. Nevertheless, there are only few studies on the performance of downsized [4] or full-scale [5] scrubbers for nanoparticle removal. As regulatory frameworks on particulate emissions intensify, bridging the knowledge gap on nanoparticle collection by wet scrubbers in WIP becomes of great importance. The aim of this study is to present an original methodology to consider, based on numerical particle collection efficiency, for the design of a pilot-scale scrubber intended to be operated on-site of a WIP and fed with the real fumes, with an attempt to evaluate wet scrubber performance in collecting flue gas nanoparticles...

The use of various raw materials in the form of bulk materials takes place in the building materials industry, agriculture and the food industry, among others. Bulk material handling, transport and storage result in the particle emissions, referred to as dusting.

The aim of the project is to demonstrate the effectiveness of the dust reduction measure "use of spray nozzles" in combination with the effect of electrostatic charging. The special feature here is that the investigations are oriented to the type of stress and the material and thus take into account the character of the dust emissions in a macroscopic scale. Different test set-ups are used to realistically illustrate the bulk handling operations during which dust is released. The effectiveness of the reduction measure is investigated using different operating parameters for dust emission as well as separation. The subsequent electrostatic charging of the spray mist allows the use of water and compressed air to be reduced. An evaluation method for spray nozzle systems is being developed, which considers the economics of the used resources and the material-related efficiency of the dust reduction, with a focus on the fine particle fractions PM_2.5 and PM₁...

In bulk material handling, the identification of the possible released dust is crucial. This form of particle emission can cause explosive atmospheres, induce long-term sicknesses or lead to environmental pollution. The identification of the particle mechanisms can help to understand the release process and opens the possibility to invent reliable prediction methods. The release of particles as emissions when handling a bulk solid contains complex mechanisms. It depends on various parameters which can be grouped in environmental aspects, process conditions and in material properties. The use of model bodies for experiments or simulations representing a bulk material in order to identify these mechanisms can be a tool of simplification. Already in several applications, a reference material is considered for the first and further attempts [1–3] when developing and improving simulation models.

The paper deals with the advantages of a reference material using it for investigations in development and improvement of model functions. Further, the challenges using a reference material are outlined. After analysing the named theoretical aspects, the selection process of the components of the material is introduced. Next to this, the manufacturing process is considered here as well...

In order to improve models for simulating processes including dust release, single bulk particle investigations were carried out. These investigations focus on the loading scenario “impact” and “fluid stressing”, which both can cause the release of dust particles.

The reason to deal with dust emissions resulting from the handling of bulk solids in production processes is that they can lead to environmental pollution, long-term diseases or cause explosive atmospheres. To reduce these hazards for humans and the environment, prediction methods determining the released dust mass during a process have to be developed. In order to improve dust release simulations a project collaboration between the Institute of Particle Technology (University of Wuppertal) and the Chair of Mechanical Process Engineering and Solids Processing (Technische Universität Berlin) focuses on the development of these methods. The investigations are carried out experimentally and numerically...

By mixing heterogeneous particle systems, materially different particles can come into direct contact with each other (hetero-contacts), so that new special properties can arise through the resulting interface or in the contact between the different components. The resulting particle systems are also called hetero-aggregates. The overall objective of this research project is to contribute to the development of new particulate products based on hetero-aggregates formed in the gas phase. To achieve this goal, a jet-based process of direct mixed aggregation in the gas phase is to be generated, which enables the controlled formation of hetero-aggregates in suitable quantity and quality...

The development and optimization of equipment aimed at removing nanoparticles from atmospheric air has been gaining importance in the current scenario. The adverse effects of these ultrafine particles on human health and the environment motivate the development of techniques for their removal, both for the processes’ sustainability and the mitigation of pollutants. Among the commonly used equipment, electrostatic precipitators stand out for their versatility and, for certain configurations, efficiencies are up to 99.9% in a wide size range.

The present study aims to evaluate the influence of the electric field and spacing between wires in the collection of polydispersed NaCl nanoparticles...

Electrospinning is a promising method for the production of filter media for air treatment. This technique allows to obtain fibers in a nanoscale in a simple way and with different morphologies. Aligning this with the possibility of recycling waste increases the potential contribution to the environment and society. Among materials, expanded polystyrene (EPS) represents a major global problem due to its inadequate disposition and difficulty recycling. However, producing fibers by reusing materials is a challenge due to the difficulty of keeping the fibers’ properties constant. In addition, large-scale production should be economically viable, leading to the need for research in order to produce resistant filters, with high filtration efficiency and low pressure drops. Thus, the present work aims at the development of nanometric fibers with good efficiency, low pressure drops and high resistance, from EPS...

Pulse-jet cleaned filters are commonly used for the separation of particles from dust-laden gas streams for the purpose of product recovery or environmental protection. While past research focused on e.g. minimizing dust emissions, energy aspects are gaining relevance in the context of rising energy-costs and tackling climate change.

While the differential pressure between the raw-gas side and the clean-gas side of the filter is one major indication for the energy demand, the required consumption of pressurized air for the jet-pulse also has to be considered in a total energy balance. Filter operation allows for a variety of parameters (e.g. cleaning frequency, tank pressure for filter regeneration, valve opening time, etc.) to be adjusted that have an impact on energy demand and dust emissions. While frequent cleaning of the filters creates a low differential pressure level, the consumption of pressurized air may become considerable. Additionally, particle penetration is predominantly possible only after cake detachment so that emissions presumably increase for shorter cycle times. Höflinger et al. proposed a method for the evaluation of filter media under energy considerations for filter test rigs, taking into account the contribution of differential pressure as well as pressurized air that can be transferred to actual filter operation in order to evaluate filter performance regarding energy aspects.

In this study, the operation behavior of a pilot-scale baghouse filter with a total of nine filter bags (needle-felt filter medium) was analyzed regarding energy consumption and particle emissions...

Fabric dust collectors work by drawing dust laden gas through a semi-permeable fabric which is usually constructed in the form of tubular sleeves, longitudinal envelopes or pleated elements. As the gas passes through the fabric, the particles in the gas stream are retained, leading to the formation of a layer of dust on the surface. This is normally referred to as a ‘dust cake’. After a period of time, the accumulated dust leads to a reduction in the permeability of the material, and creates an increased pressure drop. Consequently, the fabric must be cleaned at appropriate intervals to return the pressure drop to a more acceptable level. Dust is then again collected and the filter continues through cycles of dust accumulation and cleaning. Earlier the work carried out by Mukhopadhyay and Chaudhary the following conclusion is drawn: All the pressure parameters (peak pressure, residual pressure and cake pressure) decrease with an increase in cleaning pulse pressure (higher cleaning intensity) and fibre denier in the media. Furthermore, at any level of pulse pressure and fibre fineness, all the aforesaid pressure parameters increase significantly from the unsteady state to the steady stage of operation. Interaction effects among pulse pressure and fibre denier in filter media becomes very large with the passage of filtration time. This implies that the role of dust-fabric interaction on various pressure differentials becomes prominent at the steady state of filtration operation. At steady state, pulse pressure can be set at a lower level for media made up of coarser fibre and vice versa. This will result in...

Pulse jet is a well-established technique for cleaning of fabric filters, which consists in exploiting the mechanical (shaking) action of a pressure wave produced by a compressed air jet and travelling across the bag filter to remove the dust cake from its surface. Considerable attention has been devoted to making the process more efficient and cost-effective, resulting in a collection of best practices and guidelines obtained from the professional experience of practitioners, often complemented by experimental testing on pilot plants at the laboratory scale. Here a different approach is adopted, namely, the computer simulation of the air flow through Computational Fluid Dynamics (CFD) techniques. Thanks to the constant increase in computer power and capability of simulation software, CFD is now used in any engineering area involving fluid flows. Key advantages of CFD compared to the more traditional laboratory testing are the large amount of distributed information that a computer simulation can provide, the (relatively) low economic cost, as well as the (virtual) possibility to simulate any type of flow process regardless of its complexity and geometrical scale. However, from the point of view of the user, the main drawback is the high computational burden of the simulation, intended as the combination of calculation time and memory requirements. In almost all cases of engineering relevance, such as for instance those involving turbulent flows, the fluid flow equations obtained from the basic physical principles, i.e. mass, momentum, and energy conservation, must be first mathematically manipulated and then numerically approximated to be handled by a computer. This produces a number of coefficients, parameters, and closure equations which are, in the end, not well characterized and empirical in nature. These must be decided by the user, thus, creating uncertainty and possible lack of confidence in the simulation results. So, the real challenge of CFD users is not only (and not so much) to solve the equations but, rather, to ensure that the combination of settings (sub-models, parameters etc.) allows for reliable numerical predictions.

The present contribution aims at disclosing the potential of CFD in the application to pulse jet cleaning of fabric filters. Indeed, some studies have been already published in which CFD was used to simulate the process; however, most of them are either pioneering explorations (e.g., Laux et al., 1993) or recent investigations shedding some light on the functioning of the entire cleaning line (e.g., Anderson et al., 2016). Conversely, the scope of the current work is to assess the actual capability of CFD as an effective engineering tool, satisfying the requirements of accuracy, robustness, and computational performance...

In many systems, multiple filter elements are used to increase the filter area. Typical examples are dust filter plants with hundreds of single filter bags or cartridge filter plants with several filter elements. The crucial factor for an efficient use of the installed filter area is a uniform loading of the filter area. However, this cannot always be achieved on the upstream side, especially if the filter system has to be individually adapted to the constructional conditions. If the filters are not loaded evenly, this can easily lead to increased operating costs due to high pressure loss, frequent cleaning, damage to the filters and thus shorter service lifetimes of the filter system.

The contribution presents a simulation tool based on flow simulations (CFD) for filtration plants. The simulation tool is based on the open-source CFD toolbox OpenFOAM. In the modelling approach an Euler-Lagrangian formulation for particle transport and a porous media representation for the filters are used. The interactions of local loading on the filter segment, the local resistance increase due to particle deposition and the resulting shift of the continuous flow are considered in an iterative approach.

This modelling approach has been extensively extended with regard to multiple filter systems in order to represent these systems efficiently....

A new, clean filter medium for surface filtration always starts with the initial phase in which the dust separation can be described by the principle of depth filtration in the given medium. The term filtration kinetics refers to the time behaviour of the separation efficiency of the entire filtering layer, which includes both the given medium and the deposited particles in the medium. If the dust separation on a given filter medium is carried out for a sufficiently long time, a dust cake is formed after a completed clogging phase, which is often a gradual process. A fully formed dust cake on the given filter medium has, in addition to the core region of the cake, in which the packing density practically no longer changes, a highly porous packing section on its surface, which has a characteristic, stable height profile of the packing density in the direction of the gas flow. This packing section on the surface of the dust cake acts as the actual, active separation zone of the cake for the coming dust particles, since hardly any particles penetrate into the core region of ​​the cake below. Therefore, with surface filtration which is named in relation to the original filter medium, there is always a special, highly effective depth filtration in the highly porous packing section of ​​the dust cake on the microscopic level. This special depth filtration achieves a dynamic equilibrium of the filtration kinetics in which the structure of the active separation zone in the sense of a filtering layer no longer changes.

In this study, the overall filtration process is therefore viewed from a completely new perspective: There is a continuous, systematic change in the active separation zone of a given filtering system which is transformed from the initial clean filter medium via continuous particle separation under the given filtration conditions to a new, dynamically preserved stable porous structure – this is the active separation zone of the dust cake. Results from 3D simulations of cake formation on filter models for fabric filters are evaluated and converted into a dimensionless form to describe structural changes in the filtering layer during the overall filtration process. Possible approaches to describe this systematic change mathematically are presented and discussed...

Personal cyclone samplers have been widely used to measure the respirable mass of particles in occupational and ambient environments. In respirable dust sampling, it is essential that the cyclone cut-off characteristics be known and constant, and that each cyclone be operated at a flow rate which produces the desired cut-off. The personal sampling methods used today comprise air flows up to 10 l/min. The aim of this work is to develop a 20 l/min sampling cyclone that meet the respirable convention. This was realised by using Computational Fluid Dynamics (CFD).

The particle-laden flow within cyclone samplers has been investigated with LES applying a dynamic Smagorinsky-Lilly subgrid-scale model. The air phase was treated using a Eulerian approach while the Lagrange method was applied to model the movement of particles, which were tracked through the cyclone. CFD simulations have been validated based on experimental measurements of pressure drop and penetration.

Two cyclone designs, Higgins-Dewell (HD) family and GK family, have been computationally investigated at a flow rate of 20 l/min and the flow pattern, cyclone pressure drop and particle penetration have been analysed....

Indoor air cleaners are widely used to improve the indoor air quality and can contribute to reducing infection risks by filtration of virus-carrying droplets. There are several test standards using sealed, well-mixed and unfurnished chambers to determine the clean air delivery rate (CADR) as a measure for the cleaning performance. However, there is only limited knowledge on how the results transfer to real applications and how several air cleaners in the same room interact with each other. Moreover, the detailed distribution of cleaned air can be experimentally obtained only with low spatial resolution. Here, computational fluid dynamics (CFD) simulations can deliver additional information after a validation with experimental results. To address these aspects, we considered three scenarios typical for the application of air cleaners.

Firstly, we investigated the effect of the position of the air cleaner in a 63 m³-sized meeting room. Paraffin particles were dispersed with an atomizer and the decay of the particle concentration measured in different size ranges and at different locations without and with one or more air cleaners operating. We show that the cleaning efficacy is nearly independent of the position of the air cleaner. The cleaned air can be homogeneously distributed even in the presence of flow obstacles such as acrylic glass sheets, which are often used to prohibit direct infections between individuals. Furthermore, we demonstrate that the combination of two air cleaners operated at a lower flow setting can have the same cleaning effect as a single air cleaner at higher flow setting, but at a lower power consumption and less nuisance due to noise.

In a second step, experiments in a 200 m³-sized classroom were performed. Firstly, the most realistic situation with about 30 pupils in the room, inducing a natural airflow by their body heat and activities, was considered. In this case, particles entering the room when opening the windows were used as test aerosol. After closing the windows and operating the air cleaner, the decay rates were measured to determine the CADR. For comparison, measurements in the unoccupied room using an artificial source of NaCl particles were performed. We show that both measurements are in reasonable agreement. This means that the efficacy of an air cleaner can be determined to good approximation on site using surrogate particles and without the presence of persons in the room.

Finally, a 260 m³-sized open-plan office equipped with two identical indoor air cleaners was chosen to validate numerical simulations with experimental data. While many studies in the past have used Reynolds Averaged Navier Stokes (RANS) approaches for predicting the particle propagation, the turbulence length scales accurately captured in these simulations might not be sufficient to provide a realistic spread and mixing of particles under the effects of forced convection. Thus, here a Lattice Boltzmann Very Large Eddy Simulation (VLES) approach was applied. We investigated both the cleaning of an initially contaminated room as well as the steady state situation reached in the presence of a continuous particle source. Both simulations and measurements with salt aerosol particles were...

Though particles below 0.3 µm are not considered in ISO 16890 filter classification, they are critical to human health because of high number concentrations in ambient air, respirability and lung deposition together with the ability to cross the blood/brain barrier. Increasing air filter efficiency usually requires denser filter material when using only mechanical filtration principles, which leads to higher energy consumption of ventilation devices in the system. Filters based on mechanical separation usually show a minimum efficiency between 200 and 400 nm, which can only be increased on the cost of high air resistance of the filter medium. Therefore, alternative principles combining low pressure drop and high removal efficiency are of interest, such as electrostatic aerosol separation. Generating ionized air upstream of a standard coarse filter material is supposed to improve filter performance significantly, especially at nanometre particle size range.

The aim of this research was a better understanding of ionization induced aerosol separation principles, as well as of interactions and dependencies with existing technical components. Based on experimental data, conclusions for the further development and application in air filtration systems should be formulated. Suitable measurement methods had to be developed.

Within the presented study, prototypical components for ionization and standard filtration materials were characterized, the combination of both was investigated at lab scale and basic design principles were derived. The potential of separation improvement by this technology should be quantified....

Management of infectious bioaerosols in indoor air has emerged as an important technology due to the COVID-19 pandemic. Bioaerosol management can be divided into physical capture and physicochemical inactivation steps. KIMS is researching technologies to inactivate physically captured aerosols with dielectric filter discharge.

The plasma filter generates surface plasma on the porous ceramic to oxidize the bioaerosol captured in the ceramic foam, and supplies reactive oxygen species including ozone to the polymer filter located at the rear for secondary oxidation. Ozone emission, an inevitable problem of atmospheric pressure low-temperature plasma technology, has been solved through a catalyst, and ozone concentration of 0.05 ppm or less can be maintained for more than 200 hours. It was demonstrated that the SARS-CoV-2 aerosol was inactivated by more than 99% immediately after passing the plasma filter.

In this presentation, we will briefly introduce the developed technologies and report the commercialization results.

Both stationary ventilation systems and mobile air purifiers can remove potentially harmful aerosol particles from indoor air by either capturing them in a highly efficient filter medium or by exchanging aerosol-laden air with fresh air. During the pandemic, focus on health protection was typically the most pressing need - often without taking the energy efficiency of the measures into account or adapting volumetric fluxes, and thus, energy consumption, to the actual or current aerosol pollution.

Therefore, the aim of the funded project ESTATE is to evaluate for a given demonstration room various scenario for reducing particle concentration with regard to their energy efficiency. Measures to improve energy efficiency are considered at both component and system levels. Reference cases will be developed combine measures for optimal performance w.r.t. energy efficiency and air quality level. Measures are evaluated based on digital technologies such as sensor networks, flow simulation and cloud-based data analysis. Improved energy efficiency at both component and system levels is to be achieved through the further development of technology and in combination with artificial intelligence. The results should provide building blocks for the COVID-19 pandemic in the short term and for potential future infectious diseases that can be transmitted by aerosols in the longer term, which offer a stable level of health protection and actively promote the achievement of climate targets through CO₂ savings using digitalised, energy-efficient solutions.

A progress report of the ongoing research will be presented, using thermal manikins and a spatially resolved sensor network comprised of sensor nodes that are able to monitor air quality, and the air velocity vector. The transport of aerosol particles will be studied inside a lecture hall under three different configurations: using the hall’s own stationary air handling unit, using a mobile air purifier, and using both. In addition to aerosol particle concentration, the results of thermal comfort will be presented along with environmental parameters such as temperature, relative humidity, and CO₂ concentrations. Finally, CFD models will be setup and validated for both aerosol particle transport and thermal comfort, as defined by predicted mean vote (PMV) and percent of persons dissatisfied (PPD) parameters. Based on heatmaps of the clean air delivery rate, the critical response time of the sensors, and of PMV and PPD we show that...

With the continual increase in air pollutants due to industrial and technological activities, air quality has become an important area of concern in recent years [1]. Particularly, high number of pollutants have been detected in indoor air which may be two to five times higher than the outdoor level. These pollutants which are mostly particulate matters (PMs) with harmful microorganisms have posed a great threat to human health [1,2]. One of the promising methods to remove PM from indoor air is using air filters in air conditioners whereas air conditioner with UV module can be an effective device to kill pathogens [3]. For PM reduction, porous and fibrous filters particularly high-efficiency particulate air (HEPA) filters, intense field dielectric (IFD) filters and electrostatic filters have received a great attention since they effectively capture PM and maintain low pressure drop at air conditioners [4]. HEPA filters capture particles via adsorption. IFD filters work as a magnet to pull particles out of the air with electric field as they travel through the filter. Electrostatic filters are mostly positively charged filters and capture negatively charged PM which obtained via an ionizer. However, the best filter with high PM reduction capacity, low energy consumption, high selectivity and zero by-product invention is still unclear and there are various standards to follow. Therefore, it is necessary to investigate a comparative study among the filters to decide the best filter for PM reduction via providing microorganism elimination. In this study, we explored PM reduction performance of HEPA, IFD, electrostatic filters. Performance of filters were tested in an air-conditioner and effects of PM concentration in the air and slot number of filters on their PM reduction performance were investigated. For electrostatic filters, effects of presence and number of ionizer, position of ionizer on air conditioner and the distance between the ionizer and the filter were also examined. Microorganisim removal functionality...

Cleanrooms are critical environments in many industries, such as micro-electronics and pharmaceuticals. Contamination control has been a necessity for semiconductor processing since its beginning more than 50 years ago. Over time, the semiconductor industry has evolved cleanroom designs to minimize impact of Airborne Molecular Contamination (AMC), gas-phase chemicals of organic and inorganic nature, typically at parts per billion (ppb)-level ambient concentrations. AMC is introduced from outside and from internal sources and dispersed into the cleanroom environment, where it can cause damage to process tools, induce defects and reduce product yield.

To minimize airborne contamination and localize its impact, semiconductor cleanrooms are operated under laminar air flow from top down, entering through ceiling Fan Filter Units (FFU) and exiting through open floors. AMC filters are employed in conjunction with ULPA particle filters on top of FFUs to adsorb AMC. However, laminar flow patterns of the incoming air are often disrupted and altered by the process tools spread out over the cleanroom area. Therefore, to maintain ultra-pure air quality of the clean room, it is important to understand AMC concentrations and flow profiles around the process tools such as scanners, clean tracks and metrology tools.

Computational Fluid Dynamics (CFD) modeling has been proven to be an efficient and productive tool to understand physical behavior of air flow and airborne contaminant concentrations in cleanroom environments. CFD can be employed to create virtual prototypes of cleanrooms and offers insights into air flow and AMC concentration profiles through the interaction of mathematical models with varying cleanroom layout parameters.

This study demonstrates a CFD modeling approach to simulate air flow patterns and the distribution and mixing of AMC in semiconductor cleanrooms...

Emissions from gasoline engines and brakes of commercial or municipal vehicles as well as by metro or train contribute to health problems and premature deaths. These existing vehicles will continue populating the roads for the next decades emitting PM10/PM2.5 exhaust particles and toxic secondary emissions. For immediate reduction, retrofit filtration solutions for tailpipe and brake wear emissions must be brought to the market. Timing is crucial as retrofits are transition technologies until full electrification of Europe’s transport fleet. But even beyond, brake retrofits may still play an important role in the electrified fleet.

AeroSolfd, a Horizon Europe Innovation Action, addresses quick wins in the reduction of the overall footprint of the existing fleets by developing retrofit filtration devices for tailpipe, brake, and closed environments. The focus is on reducing particle/NOx for tailpipe and brake emissions. This can be filtering emissions at the source (tailpipe and brake) or filtering the air at metro stations as example of semi-closed environments to reduce the overall exposure. Currently, retrofit devices do not depend on legislation like upcoming EURO 7. Nevertheless, there is a need for public awareness, incentives, and policies to support the implementation of the filtration devices and for a market ramp-up. Moreover, the retrofit solutions should also contribute best possible to high innovation governance standards considering safety and overall sustainability along the entire life cycle of the products. The innovation project consists of pillars A) Development to bring existing retrofit technologies from TRL 4-7 to TRL 8 and B) Market preparation including sustainability assessment, public awareness, stakeholder engagement and proposal of incentive schemes.

We will present the overall project setup and scope of the Horizon Europe Innovation Action AeroSolfd. The status quo of the filtration devices will be described. The focus is on the development from TRL 4-7 to TRL 8 of the brake dust particle filter and the filtration solution for (semi-)closed environments. The ongoing developments as well as the methodology considered for the next steps will be presented. Preliminary results on how to assess the status quo of brake emission on city bus routes and about the passengers’ exposure at metro stations will be discussed in detail...

Since the emergence of the COVID-19 pandemic, transmission of viruses in indoor environment has become one of the major focuses of research. This is not only limited to hospital environments and other public facilities such as schools, but also means of transport ranging from high capacity public transport systems such as airplanes and trains down to individual transport methods such as cars have become areas of interest. Prolonged stays in closed environments can increase the risk of transmitting airborne biological particles, therefore appropriate ventilation and filtration of the indoor air is of high importance with various strategies and devices, such as air cleaners and HVAC being tested.

Currently, HVAC systems and air cleaners, as well as car ventilation systems and indoor cabin filters are primarily tested within laboratory conditions on filter test rigs or in enclosed test chambers using standardised plasticizer aerosols or mineral particles such as DEHS or smoke. The drawback to this approach is, while these test aerosols represent the bioaerosol particle size, they do not evaluate whether the filtration or cleaning mechanisms lead to significant inactivation of potential biohazards. With the focus on car cabin air cleaning, the aim was to develop a standardized method for testing car ventilation systems directly in cars under real-life conditions: on the one hand and carrying out said testing with phi6 bacteriophage bioaerosol, serving as virus surrogate, on the other hand to investigate actual decreases of viral activity within the enclosed car interior.

Zero emission cars are one key to reach cleaner environment. However up to now it`s still a long way to reach that goal.

In the past the standards like the ISO 5011/ ISO TS 19713 for Engine Intake Filter to protect the engine and it`s performance, ISO 17536 for Crank Case Ventilation Filter to reduce the aerosol emissions, were very common in the automotive application, as well as the ISO 11155 Cabin Air Filtration for the protection of the passengers.

The Particle Measurement Programme or PMP is a programme for advancing the particle measurement technique for particulate vehicle exhaust gases. This was seen up to now the main driving for the car emissions, which lead us to the DPF filters in the automotive section. Recently the PMP test equipment shift their cut off size from 23 nm down to 10 nm.

In the automotive area there are several approaches in the past as well as upcoming guidelines to reach a zero-emission car.

Some approaches and research are nowadays done on the tyre abrasion, as well as on the brake emissions. The goal is to get a full footprint of the car emissions. The problem in that case is the output of fine dust as well as microplastic caused by abrasion of tyres and brakes. With the upcoming EU 7 standard the brake emission guideline GTR Proposal on Laboratory Measurement of Brake Emissions for Light-Duty Vehicles is on the way. Within the GTR Proposal the particle number counts as well as the PM 2.5 and PM 10 values are now in the focus. The solution is a brake dust emission filter which lead us closer to a zero-emission car and cleaner air.

Some zero emission cars are even available on horizon, like Prototype Zero Emission Drive Unit – Generation 1, the ZEDU-1. This car was developed by DLR (Deutsche Zentrum für Luft- und Raumfahrt) and the automotive company HWA. The ZEDU-1 was first introduced to public on the 28^th of September 2022 on the Karlsplatz in Stuttgart, Germany.

There is still a long way to go until zero emission cars will be something normal. We like to show in this paper some solutions and measurement concepts to reach that goal...

Reduction of particle emissions from the mobile sector has worldwide focussed on diesel engines. Limit values have been introduced from 1982 and today the diesel particle filter DPF is a standard component for HD and LD vehicles as well as for offroad machines. Petrol engines however have never been controlled for particle emissions, nowhere on the globe until 2017 when new DI petrol engines received a PN limit value, still higher than diesels. The simple reason was, that diesels can and sometimes do smoke and petrol engines have a non-smoky transparent exhaust gas.

Research however knows that petrol exhaust is only transparent because petrol particles are smaller than diesel particles an thus invisible. Research also knows that smaller particles are easily penetrating alveoli membranes and thus effect health stronger. These small particles may even be smaller than size cut-off of actual EU-particle metrology thus they may not even be detected today. On the other side we have to take note that worldwide vehicle fleets contain many more petrol engines than diesel engines and since new research has revealed that particle number concentration of petrol engines can be orders of magnitude higher than with diesels, we have to worry about a carcinogenic pollution effect which today is not recognized by emission statistics, not even in the USA and Europe, a hidden health thread, maybe the largest.

A technology is needed, which must be flexible enough to also be applied to in-use vehicles and the EU looks for a technical demonstration proving that this technology can be made available within three years at reasonable implementation cost. Within the AeroSolfd project we will therfore investigate a statistic sample of 1000 vehicles for ultrafine particle emissions in order to get a feeling about the size and urgency of this problem and we will retrofit 50 vehicles of different brands in three different countries. We also would like to think outside the box based on fleet analysis in Mexico city where VERT has analysed 400‘000 vehicles with shocking results with respect to the high emitter effects.

But do we have the technology? DPF cannot just be applied to petrol engines like to diesels, since DPF only filter efficiently after a soot layer has been build up on the ceramic filter wall since the average pore size of the ceramic wall is around 10 μm and the diesel particle might be as small as 100 nm. Petrol engines however do not build up this filtering soot layer, so a petrol engine with a DPF may only filter < 70% which is by far not good enough.

Quite recently new pore structure technologies have been developed, called membrane technology or hierarchic pore structure technology, which promise much better results. These technologies have been already pre-tested and demonstrated particle filtration in the size range of 10 nm – 500 nm of over 99% even with the brand new filter or fully regenerated.

Another problem must be solved to detoxify exhaust gas of petrol engines, which is the high concentration of PAH coated on these particles which might become desorbed even between regeneration phases which requires an additional catalytic activity to be included in this system.

The paper will present the best available technology for this project and first results with different GPF with respect to size specific filtration and toxic gaseous emissions.

Air pollution is one of the biggest health risks worldwide. The toxicity of particulate substances depends on quantity, particle size as well as chemical composition. The smaller the particle size the deeper particles can penetrate the human body. Particles with a size smaller than 0.1 µm can enter the lung tissue and then the bloodstream. As a result, these particles can cause not only acute and chronic lung diseases, but also cardiovascular diseases. In addition to classical organic and inorganic pollutants, the recent COVID pandemic has increased concern and understanding of the impact of micro-organisms and bacteria in the atmosphere. Consequently, awareness regarding air pollution and its consequences is increasing worldwide. The level of fine dust increases with higher traffic volume with increasing levels of particles entering the cabin of the car. State-of-the-art cabin air filters consist of different filter layers. In many systems, the particle filter layer is a so-called electret filter medium. Such filter media offer an acceptable initial retention at a relatively low differential pressure. However, during the lifetime of the element, the filtration efficiency decreases dramatically. The efficiency in the microscale particle size range can drop under 10 %. Consequently, different car manufacturers have introduced solutions that rely more on mechanical rather than electrostatic filtration. Since the permeability of those media is much lower the required filter size can be–depending on the targeted efficiency level –up to 10 times compared to state-of-the-art cabin air filters. Alternatively, utilizing those media in existing small package the pressure drop and consequently the energy demand of the system increases by a similar order. Hengst Filtration has developed an innovative filtration solution that achieves high filtration efficiency on compact space at a low pressure drop. This is achieved through electrification of the system using a combination of ionization and polarization. Ionization provides the particles with a very high level of electrostatic charge making them more likely to be captured in an electret filter medium. Polarization of the filter element leads to a conservation of the charge distribution within the filter medium. Therefore, the high initial filtration efficiency can be conserved over filter lifetime.

In the presentation, the effects of ionization and polarization alone as well as in interaction are presented. The filtration performance of the electrified filter system under various conditions will be discussed...

The research work presented here is related to 3wheeler Autorickshaw actual vehicle air filter performance comparison with testing laboratory results. These vehicles are used in India for commuting between cities, towns and near by villages by the urban and rural village men and women.

Since these vehicles are used very frequently, day and night by the country men, it is necessary to take care of their health, air pollution and reduction of emission of toxics gases, etc. Hence it is necessary to have highly efficient air intake system in engine.

The comparison of laboratory results which were tested according to ISO5011 standard of air filters, indicates that the actual conditions were very much safer with respect to above parameters. This study was done for air filter testing before fitting on vehicle and after vehicle running for 20,000 kilometres. The pressure drops, initial and full life efficiencies and element dust holding capacities were studied. This study helped to predict better mileages and air filter element service life increased by 65%. Another objective of this study was to understand the difference between laboratory test results and actual performance as actual tests are not possible to conduct every time as they are time consuming and not feasible due to various real-life conditions...