Performance Of Air Filters Research Articles

Theoretical investigation and experimental validation on transient variation of particle concentration in a simulated consulting room in hospital

At present, the ceiling cassette fan-coil unit (CCFU) is widely used in Chinese hospitals. However, enough attention has not been paid on filter installation in CCFU. This will cause secondary pollution inside the CCFU, which may increase the risk of nosocomial infection. With the increasingly serious condition of atmospheric pollution and the complexity for coexistence of bacteria and virus in hospital, it is urgent for owners and operators of hospital to select suitable filters for CCFU. In this study, three kinds of air filters (G4, M5 and F7) were installed in a consulting room, respectively. Indoor air was re-circulated by CCFU. The performance of air filter was evaluated by monitoring the decay rate of particle concentration within a period corresponding to the average regular consulting time. It is found that the overall particle removal efficiency (via filter-integrated CCFU) (OPRE) increases with the increase of filter's classification level. Upgrading the G4 filter to M5 or F7 filter can significantly reduce indoor particle concentration. Compared with F7 filter, the performance improvement of the M5 filter is mainly obtained for particles with diameter 0.85–3.5 μm. As far as the dynamic variation of particle concentration in the period studied is concerned, there is an exponential relationship between OPRE and clean air delivery rate (CADR). Since the concentration of bacteria is correlated to that of particles with diameter close to 3 μm, it is suggested to install M5 filter for this application, which provided the basis for selection of filter in CCFU for hospitals.

Tailoring Supramolecular Nanofibers for Air Filtration Applications.

The demand of new materials and processes for nanofiber fabrication to enhance the performance of air filters is steadily increasing. Typical approaches to obtain nanofibers are based on top-down processes such as melt blowing, centrifugal spinning, and electrospinning of polymer materials. However, fabrication of polymer nanofibers is limited with respect to either a sufficiently high throughput or the smallest achievable fiber diameter. This study reports comprehensively on a fast and simple bottom-up process to prepare supramolecular nanofibers in situ inside viscose/polyester microfiber nonwovens. Here, selected small molecules of the materials class of 1,3,5-benzenetrisamides are employed. The microfiber-nanofiber composites exhibit a homogeneous nanofiber distribution and morphology throughout the entire nonwoven scaffold. Small changes in molecular structure and processing solvent have a strong influence on the final nanofiber diameter and diameter distribution and, consequently, on the filtration performance. Choosing proper processing conditions, microfiber-nanofiber composites with surprisingly high filtration efficiencies of particulate matter are obtained. In addition, the microfiber-nanofiber composite integrity at elevated temperatures was determined and revealed that the morphology of supramolecular nanofibers is maintained compared to that of the utilized polymer nonwoven.

Modeling unsteady filtration performance of pleated filter

ABSTRACTThe dust loading has a significant influence on the transient performance of air filters. This study developed two models based on the Lagrangian and Eulerian methods to simulate the unsteady filtration process in the pleated filter. The flow field through the filter was calculated by solving the Navier-Stokes equation with the DES-SA turbulence model. The filter media and the cake layer were modeled as the porous zone. The Lagrangian method tracked the particle trajectories to model the particle motion, but the Eulerian model treated the particle as continuous phase. Two cell models were proposed to simulate the transient particle deposition and the cake layer growth on the filter medium surface for the Lagrangian and Eulerian methods, respectively. The simulated results were validated by the available experimental data. Both of the methods could provide relative accurate results with acceptable error. But the computing speed of Eulerian model was faster than the Lagrangian method. Otherwise, the...

Photocatalytic Cleaning Performance of Air Filters for a Binary Mixture

Photocatalytic Cleaning Performance of Air Filters for a Binary Mixture

The key energy performance of novel electrostatic precipitators

Energy consumption of a filtration system depends largely on the pressure drop across the air ducts. The magnitude of this pressure drop is largely dependent on the presence of air filters designed to remove particles from the air stream. However, evaluating the performance of air filters by looking only at their pressure drop or collection efficiency is misleading because these two factors are not linearly dependent. A more rigorous approach uses key energy performance (KEP) to assess air filter performance, because KEP involves both collection efficiency and pressure drop. This paper provides methodology for the evaluation of performance of different types of filters, comparing the KEP of one fiber-based filter and three electrostatic precipitators (ESPs). One of the ESPs is commercially available, while the other two have novel particle-trapping mechanisms developed by our research group that substantially increase collection efficiency. The results show that, although all electrostatic precipitators have KEPs of at least nine times higher than fiber-based filters, newly developed electrostatic precipitators have KEPs of nearly twice as high as their commercially available counterparts. This paper also examines how three different operating conditions affect the KEPs of ESPs, and presents an example of energy savings in a filtration system when fiber-based filters are replaced with electrostatic precipitators.

Realistic air filter media performance simulation. Part I: Navier–Stokes/finite-volume computational fluid dynamics procedures

A review of published studies of numerical techniques for air filter performance simulation shows that there are two general approaches to such simulations. One describes gases flowing through filter media as continuous fluids, influenced by the macro properties viscosity, density, and pressure. The alternate approach treats gases as molecules in random motion, impacting their own kind and solid surfaces on a micro-scale. The appropriate form for a given filter medium and operating condition depends on the gas properties and the Knudsen number (Kn) of the smallest fibers in the filter medium simulated. When no fiber Kn exceeds 0.01, the Navier–Stokes equation and finite-volume solutions should simulate filter media pressure drop and particle capture reliably, if correct particle and fiber boundary conditions, including “slip” at boundaries, are employed. In addition, fibrous media geometry must be modeled in enough detail to make simulation results match experimental data. Part I of this study reviews literature related to filter media flow and particle-capture simulation in the continuum regime using the finite-volume method for flow calculations; appropriate boundary conditions and parameter values are suggested. Part II discusses media simulation in flow regimes where other equations and computation techniques must be used.

Effect of Treatment with a Natural Extract of Mukdenia Rossii (Oliv) Koidz and Unipolar Ion Emission on the Antibacterial Performance of Air Filters

Airborne microorganisms are deposited on air filters when these are used to reduce aerosol concentrations in indoor environments. These microorganisms cause various undesirable effects, such as production of unpleasant odors and re-suspension of bacterial and fungal spore bioaerosols into the indoor air. To resolve these issues, we investigated the antimicrobial effects of a natural extract of Mukdenia rossii (Oliv) Koidz and unipolar ion emission against bioaerosols deposited on air filters. The experimental results showed that the natural extract had an antimicrobial effect on the deposited bioaerosols, and that unipolar ion emission enhanced the antimicrobial performance of the natural extract.

Using Field Measurements of Air Filter Performance and HVAC Fan Energy Measurements to Select Air Filters with Lowest Life Cycle Cost

ABSTRACT Properly selected and maintained, building air filters provide a simple and often overlooked opportunity for significant reductions in electric energy use. These savings can be achieved while maintaining or enhancing indoor air quality (IAQ) by filtration of incoming and recirculated air in building HVAC systems. This article reviews the technologies behind air filtration in buildings and describes methods to select air filters and to measure electric energy use from fans and blowers, as well as the field performance of particulate air filters. Using the criteria described, air filters and energy use are evaluated in several common settings, including offices and mixed-use buildings, manufacturing plants, laboratories, and hospitals. Several case studies are briefly described, showing in-situ filtration performance, electrical energy measurements, life cycle cost calculations, and total cost of ownership for air filters of various designs and qualities. Air filter performance is characterized usi...

Performance of air filters cleaned by supercritical carbon dioxide

A new technique based on the use of supercritical carbon dioxide (CO 2) for cleaning HEPA filters was developed. Glass fiber filters and polytetrafluoroethylene (PTFE) membranes loaded with dioctylphthalate (DOP) droplets were cleaned with supercritical carbon dioxide under various conditions. The cleaning performance was evaluated by the weight recovery of the filter media and the recoveries of their collection efficiencies and pressure drops. The extent of DOP removal from glass fiber filters was nearly complete with supercritical carbon dioxide cleaning at 20 MPa and 40 °C for a period of 120 min and the collection efficiency and pressure drop were also recovered to those of new filters. Furthermore, thermo-gravimetric (TG) analysis showed that cleaning did not wash away any of the binder resins. However, less satisfactory results were obtained for PTFE membrane filters.

Importance of characterizing a reference filter test system

Standards governing the performance of air filters are there to enable comparisons to be made between different filter tests. However, measurement data from different filter test systems can vary widely, making comparisons difficult. Palas GmbH, Germany, has developed a modifed test system that it says meets the minimum requirements of a reference filter test system.

イメージングプレートを利用したエアフィルタの捕集性能の簡易評価法

Collection performance such as collection efficiency and surface collection efficiency is considerably important in order to select a suitable filter for the measurement of the concentrations of airborne radioactive particles. A simple method with imaging plates is proposed to evaluate the collection performance of air filters. By comparing the collection performance of some filters with natural airborne radioactivity as a test aerosol, it was confirmed that the method could reliably evaluate the collection performance of filters.

Study of Performance of Air Filters in Public Shelters

Study of Performance of Air Filters in Public Shelters

Characterization of Silica Particles Generated with Raskin Nozzles and Their Application to Air Filter Performance Tests.

Characterization of Silica Particles Generated with Raskin Nozzles and Their Application to Air Filter Performance Tests.

Method for investigation of various iodine species in the primary coolant of the Nuclear Power Plant in Paks

Iodine isotopes formed in the course of fission in nuclear reactors may be present in the primary coolant in different oxidation states, i.e., in different chemical forms. It is important to know the chemical forms and their proportions in order to asses the environmental effect of the emitted iodine and the performance of air filters used in the primary circuit for binding iodine species, since both depend on the chemical forms in which it is present. Volatile components were separated from water samples taken separately from each block of the nuclear power station by purging with inert gas, then the aerosol, iodine vapour and alkyl iodides were selectively bound on the filter system of the “KOMBI” sampler. I 3 − , I−, IO−, IO 3 − and IO 4 − left in the aqueous phase after purging were separated by consecutive physical and chemical procedures (extraction, isotope exchange, reduction). The results of the investigations have shown that the water technology used in the Nuclear Power Plant in Paks is appropriate with respect to the radioiodine balance. Iodine was found to be the predominant species, and no volatile iodine species were found to be present in the primary coolant. Volatile iodine species sometimes appearing in emissions may be formed from leaching waters due to secondary effects.

Laminar-airflow equipment certification: What the pharmacist needs to know

The basic information pharmacy practitioners need to determine the suitability and applicability of laminar-airflow equipment test standards and procedures is presented. The operative guideline for any laminar-flow clean bench (LFCB) certification is the cleanroom and work station requirements for controlled environments as defined by the federal government under Federal Standard 209b (FS 209b). FS 209b outlines the tests, test procedures, and acceptable performance ranges for all LFCB equipment. National Sanitation Foundation Standard Number 49 (NSF 49) is used in the certification of biological-safety cabinets (BSCs). NSF 49 covers those aspects of safety, maintenance, performance, and testing that are unique BSCs. To monitor certification properly, practitioners should be familiar with these standards and the air-velocity profile, high-efficiency particulate air filter performance, noise output, light, and electrical test procedures. A review of the requisite knowledge, experience, and reputation of certifying agents is presented, along with an outline of all the necessary procedures, equipment, and documentation to be used in the process. A thorough test report should be issued upon unit certification. As pharmacy practitioners are responsible for all other aspects of quality assurance, they should also be capable of auditing these certifications to ensure the aseptic quality of products compounded in the laminar-airflow environment.

Evaluation of air filters with submicron viral aerosols and bacterial aerosols.

Abstract Velocity, aerosol particle size, aerosol charge, and exposure to high humidity were found to affect the performance of air filters. Filter papers and the DOP scan-tested filter units (HEPA filters) fabricated from these papers were evaluated with submicron T1 bacteriophage aerosols having a number median diameter (NMD) of 0.12 micron and with Bacillus subtilis var niger spore aerosols with a NMD of 1 micron. Penetration of submicron phage aerosols through filter papers increased markedly with an increase in velocity. Neutralizing phage aerosol with bipolar air ions resulted in 2- to 5-fold increases in penetration. Penetration of bacterial spore aerosols through the filter papers was essentially zero. Phage aerosol penetration through HEPA filters averaged 0.00095%. Spore aerosol penetration was 0.00005%. Exposure to high humidity (>95%) resulted in roughly a 3-fold increase in HEPA penetration. HEPA filters can be expected to provide excellent protection against submicron viral aerosols as well ...