Air Exhausts Research Articles

Impacts of gaps below both door and partition walls of cubicles on odorous gas transport and respiratory infection in a public lavatory

Odorous gas transport and respiratory infection in a public lavatory are highly subject to the adopted ventilation system. The gaps below both the cubicle door and the partition walls can affect the ventilation performance. This study employed a validated computational fluid dynamics (CFD) program to investigate a public lavatory containing four cubicles with squat toilets. The airflow, concentrations of hydrogen sulfide and methyl mercaptan, and respiratory infection risk during use of the toilet were modeled. Odorous gases were released from the squat pan, while the pathogens resulting in respiratory infection were released by the exhalation of the toilet users. A total of seven different gap designs were considered, including designs without any gap, with a gap below only the cubicle door in three different gap heights, and gaps in three different heights below both the door and the partition walls. In addition, the use of a single central air exhaust and the use of multiple air exhausts were compared. The results revealed that the air from the gap below each cubicle door can effectively dilute the odorous gases released from the squat pan, whereas the gap below the partition walls was not shown to be favorable. The use of multiple air exhausts restrains the pollutant's spread and reduces the respiratory infection risk.

Flow and sound field characteristics of a Hartmann whistle with flow-sound-separation feature

Acoustic agglomeration technology can arouse relative motion and rapid agglomeration for aerosol particles. Traditional electroacoustic transducers are commonly used in laboratories to produce high-intensity sound, but they are fragile and have low conversion efficiency. Hartmann whistle is a kind of air-jet generator with the characteristics of simple structure, absence of moving parts and high sound power. However, as a Hartmann whistle works, the spent airflow would be produced at the exit of the horn along with the sound field, which will push the aerosol particles away from the sound source and reduce the agglomeration efficiency. To solve the problem, this paper proposes a new Hartmann whistle with flow-sound-separation feature for the first time, and the influence of opening ratio (X/L) and inlet air pressure is studied by numerical simulation. Results show that when the opening ratio is 0.5, the air flow rate at the exit of the horn is reduced to 0 kg/h, which means that all of the spent air exhausts from the side opening. Meanwhile, the sound efficiency is decreased by 19 %. The air flow rate of the side opening increases with the increasing opening ratio or inlet air pressure. As the opening ratio exceeds 0.5, there will be backflow at the horn. The total sound power of the whistle maintains constant with the variation of opening ratio, and reaches the maximum value of 39 W at 0.275 MPa.

Ammonia Dispersion in the Closed Space of an Ammonia Engine Room with Forced Ventilation in an Industrial Plant

Air pollution is a global problem that is responsible for more than four million premature deaths each year. Air exchange in ammonia engine rooms is a priority for normal operating conditions, as well as in the event of an emergency release. A numerical approach with the use of computational fluid dynamics techniques can provide detailed data, such as spatial gas dispersion. Therefore, the objective of this study was to prepare a mathematical tool for the assessment of ammonia distribution in an engine room equipped with forced ventilation as a prediction tool for dangerous industrial setup working configurations. This study analyzed the uncontrolled release of ammonia during the production process in an engine room using Ansys Fluent software. It was observed that emergency ammonia leakage of 0.1 kg/s in the assumed air flow poses a great threat to the mechanics. In many simulated scenarios, ammonia spread to the entire building. Moreover, the mass fraction of ammonia was the highest in the gas stream right after its release. After being released, ammonia often accumulated in the ceiling zone, and in inactive exhaust chimneys, air inlets, and doors. It was observed that the effectiveness of the ventilation analyzed depended on the number of active air vents and exhausts, as well as their spatial distribution throughout the building.

Using a Micro Sampler on a Drone to Extract Organic Vapors—A Case Study of Monitoring Industrial Pollution

ABSTRACT Kaohsiung city located in the southern Taiwan is an industrial town and air pollutants were emitted from factories in the adjacent industrial zones. In order to track the pollution emission sources, a needle trap sampler (NTS), which is a micro solid phase microextraction (SPME) sampling device, was carried by a quadrotor drone to extract organic vapors from industries. The NTS was fabricated by packing divinylbenzene (DVB) particles of 60–80 mesh diameters into a 7 cm-long, 22-gauge stainless steel needle. The telescoping sampling device was carried by a DJI Mavic Pro quadrotor drone, and its effectiveness for extracting organic vapors from industrial processing air exhausts from chimneys was studied. The total weight of sampling device, including a NTS, a telescoping shaft, a Li-battery, a mini-air pump and the ABS (acrylonitrile butadiene styrene) loading frame, was less than 200 g. The mainly emitted compounds, including aromatic hydrocarbons (toluene of 1,450±650 ppb, ethylbenzene of 34±12 ppb and xylenes of 51±25 ppb), formaldehyde (50±12 ppb), alkanes (propane of 30±10 ppb), triacetin (7,620±1600 ppb) and terephthalic acid (20±5 ppb) were collected and then identified by the off-line gas chromatography (GC)-mass spectroscopy (MS) system in the laboratory. The quadrotor drone successfully monitored air pollution and tracked their emission sources from waste incineration, petroleum refinement, chemical processing and electronic part production.

Design criteria for outdoor air intakes and exhaust air outlets located on an external wall

Optimal placement of outdoor air intakes and exhaust outlets is a source control measure to avoid the degradation of air quality at the air intakes. Re-entrainment is an occasional air pollution instance that happens if pollutants in the exhaust air stream, after being discharged to outdoors, are transferred back to outdoor air intake location due to unfavorable meteorological conditions and inadequate positioning of the air intakes and exhaust outlets. In engineering practice, it is impractical to always conduct detailed dispersion modeling due to the complexity of airflow phenomena in the urban environments, and therefore, engineers rely on prescriptive design guidelines or simplified empirical models published in technical literature and regulation documents. Commonly, the design guidelines to avoid the re-entrainment phenomenon are for buildings with rooftop exhaust stacks, but the exhaust outlets might also be situated on the building façade. The objective of this paper is to overview the existing design guidelines for the placement of horizontal air intakes and exhaust outlets. Technical engineering literature, including international standards, codes, and guidebooks is reviewed to extract both qualitative and quantitative design guidelines relevant to the placement of air intakes and exhausts on an external wall.

Numerical Simulation and Experimental Research on Oil Mist Overflowing for a Giant Hydropower Generator

ABSTRACTOil mist leakage is quite dangerous to the health of the staff as well as for the safe functioning of hydro generators. In this study, a model was established based on flow theory analysis. Three-dimensional simulation was performed to determine the mechanism to calculate oil overflowing and for optimized effectiveness, and the results were proved by measured data. The results showed that negative air pressure was formed by upside airflow and caused oil mist diffusion. An optimized program could use impellers to produce air pressure drop, and exhausts and tuyeres can be used to recycle oil mist, which could reduce the oil mist rate from 4.9 m3/h to 0.36 m3/h and maintain a comfortable environment in hydropower stations.

The reduction of SOx emissions in the shipping industry: The case of Korean companies

As stricter environmental regulations for sulphur oxide (SOx) emissions emerge, the shipping industry has been deliberating new fuelling options. The three main alternatives for reducing sulphur emissions are switching to higher-quality and low sulphur fuels (commonly referred to as distillates), installing exhaust fuel cleaning structures (frequently referred to as scrubbers), retrofitting present vessels to operate as liquefied natural gas (LNG) powered vessels. Nevertheless, few studies evaluate the three existing alternatives that can reduce marine air exhausts, and fewer develop a general model for a resolution to the choice of the best technology. This study performs an empirical analysis focusing on the three alternatives considered by Korean shipping companies. The main approach involved conducting surveys and interviews to examine Korean shipping companies’ actual response to cope with SOx regulation. The results indicate that, among the nine sub-criteria regarding response to SOx regulation, investment costs (F11) are the most significant factor. In addition, through a description analysis of Korean shipping companies, this study found that there is a difference in the recognition and response direction among companies according to their size.

Comparison of air exhausts for surgical body suits (space suits) and the potential for periprosthetic joint infection

Periprosthetic joint infection is a major complication of total joint replacement surgery and is associated with significant morbidity, mortality and financial burden. Surgical body suits (space suits), originally designed to reduce the incidence of infection, have paradoxically been implicated in increased periprosthetic joint infection rates recently. Air exhausted from space suits may contribute to this increased rate of periprosthetic joint infection. To investigate the flow of air exhausted from space suits commonly used in modern operating theatres. The exhaust airflow patterns of four commercially available space suit systems were compared using a fog machine and serial still photographs. The space suit systems tested all air exhausted into the operating room. The single fan systems with a standard surgical gown exhausted air laterally from the posterior gown fold at approximately the level of the surgical field. The single fan system with a dedicated zippered suit exhausted air at a level below the surgical field. The dual fan system exhausted air out of the top of the helmet at a level above the surgical field. Space suit systems currently in use in joint replacement surgery differ significantly from traditional body exhaust systems; rather than removing contaminated air from the operating environment, modern systems exhaust this air into the operating room, in some cases potentially towards the sterile instrument tray and the surgical field.

Dry Scrubbing of Hydrogen Sulfide Gas Using Nano Zinc Oxide Coated Glass Beads

Abstract. Hydrogen sulfide (H2S) is one of the most toxic and smelly gases emitted from animal production facilities, which also acts as a catalyst poison in many industrial processes. The principal objective of this research was to develop a dry scrubber to adsorb H2S gas efficiently from airstreams mimicking air exhausts of animal and poultry barns at the ambient atmospheric condition. Nano zinc oxide (nZnO) coated 3-mm sized glass beads were investigated to adsorb H2S gas in a vertical dry scrubber setting. Colloids of nZnO were prepared and thin films of nZnO were grown on the surfaces of commercially available glass beads following a sol-gel method. The sizes of nZnO on glass bead surfaces ranged from nm to µm and found to be clustered due to the repeated coatings on the same surfaces. The energy dispersion spectroscopy (EDS) analysis confirms the presence of sulfur (S) compound that indicated a conversion of H2S into zinc sulfide (ZnS) on nZnO coated bead surfaces. The highest H2S breakthrough capacity of 2.54 mg H2S g-1 sorbent was observed. Heating the beads at 550°C regenerated glass beads effectively but experienced a gradual loss of reactivity as a number of regeneration cycles progressed. This research demonstrated that nZnO supported on glass beads are promising adsorbents for capturing H2S gas from airstreams at ambient temperature. Keywords: Airstreams, Breakthrough capacity, Hydrogen sulfide, Nano zinc oxide, Regeneration.

Numerical Simulation on Conventional Ventilation System for Hospital Operating Room

Communities in the poor countries suffer from poor quality of health services. In the Republic of Yemen as one of those countries, some hospitals especially medium and small suffer of many problems which adversely affect health community life. This paper presents a case study conducted in a hospital operating room in Yemen, also computational fluids dynamics (CFD) analysis of the airflow, and temperature distribution are presented and discussed. The operating room model includes a patient lying on an operating table, four surgical staff, two air supply and four air exhausts. Results of simulation show a good agreement with experimental data from the literature and adopted standard. It is found that the airflow and air velocity significantly affects the thermal comfort of all workers in the operating room. Therefore, the air that enters the operating room is very importance and affects the room temperature. It is observed that the application of CFD in hospitals will give rise to design the internal environment and improved health outcomes especially in a country like Yemen.

Numerical Simulation on Conventional Ventilation System for Hospital Operating Room

Communities in the poor countries suffer from poor quality of health services. In the Republic of Yemen as one of those countries, some hospitals especially medium and small suffer of many problems which adversely affect health community life. This paper presents a case study conducted in a hospital operating room in Yemen, also computational fluids dynamics (CFD) analysis of the airflow, and temperature distribution are presented and discussed. The operating room model includes a patient lying on an operating table, four surgical staff, two air supply and four air exhausts. Results of simulation show a good agreement with experimental data from the literature and adopted standard. It is found that the airflow and air velocity significantly affects the thermal comfort of all workers in the operating room. Therefore, the air that enters the operating room is very importance and affects the room temperature. It is observed that the application of CFD in hospitals will give rise to design the internal environment and improved health outcomes especially in a country like Yemen.

An Image Based Mathematical Model for the Propagation of Fan Noise in a Plenum with Large Side Openings

This paper presents another application of an images group model for a special enclosure geometry and source orientation. A previous work outlined the concept via application to a special tight-fitting enclosure. Application of the concept to a fan plenum requires different mathematical descriptions for the image groups. This paper describes the sound reverberation inside a sound enclosure with mostly open sides where the primary noise sources are the air inlets and exhausts of axial type fans located at the top of the enclosure, the sound transmission through the air inlet openings, and the radiation to wayside positions. The main reverberation between the floor and ceiling is determined with an image based mathematical model. The model considers how the main reverberant part image group is amplified by its images from two parallel bulkheads and any side wall frame members. The method of images approach allows the hard surfaces of an untreated plenum to be represented by perfectly reflecting surfaces with zero sound absorption coefficients, thus not requiring any estimate or measurement for these surfaces. Numerical results show excellent comparison to experimental results for an actual plenum. The image model is also shown to be significantly more accurate than the standard large room diffuse field reverberant model.

주민대피시설의 성능개선을 위한 실태조사에 관한 연구

purpose of this study was to conduct status survey on existing shelter facilities for residents and use it as basic material to plan and design improved shelter facilities in the future. As the result, first, although existing shelter facilities are judged to have been designed in consideration only of the protection from high explosive shells, actual protection capability is significantly low against high explosive shells when exit direction and protection capabilities of main entrances were investigated. Second, all the 7 facilities did not have air purifier with filters installed for the air that flows into the inside from outside and since the height of air exhausts and intake pipes in the outside are also close to the earth, there are possibilities that heavy contaminated air can flow into the inside. Third, although some facilities have anti-explosion doors installed, it is impossible to use them as chemical, biological and radiological (CBR) shelter because of improper installation of openings and anti-explosion valves as well as poor plumbing that cannot ensure air-tightness and poor finish of piping penetration.

Dispersion of coughed droplets in a fully-occupied high-speed rail cabin

The dispersion process of respiratory droplets released by coughing of an individual in a high speed rail cabin is studied using CFD simulations. The cabin is fully-occupied by 48 passengers with a seating arrangement of 12 rows and 4 columns. Four cases of different boundary conditions of air supply and exhausts are studied. The droplets dispersion characteristics and the maximum dispersion distances under specified ventilation conditions are studied. All 48 passengers are simulated by relatively realistic three-dimensional thermal manikins. The coughing individual is located on an aisle seat in the seventh row. The duration of a single cough is assumed to be 0.4 s; and a time-dependent coughing velocity profile is used. Within the first 10 s after coughing, a separation phenomenon of the so-called “old” and “new” droplets is observed. The “old” droplets generated in the first 0.2 s escaped from the body plume, and were injected into the lower zone of the cabin. These droplets stayed longer in the lower zone of the cabin. The “new” droplets generated in the next 0.2 s, had a relatively small velocity, and thus followed the upward body plume, entering directly the upper zone. The luggage rack also has an effect on the airflow patterns in the HSR cabin. The droplets removal ability is stronger when there is a through flow from the front door to back. However, in this situation, the droplets can disperse much further and affect more passengers.

Effects of inlet and exhaust locations and emitted gas density on indoor air contaminant concentrations

The steady-state distribution of contaminant concentrations in a workroom is a function of several factors, of which the types and relative position of air inlets and exhausts are some of the most important. Here several different inlet and exhaust locations and types (with or without diffuser) were investigated to determine the optimum inlet and exhaust positions. Room concentration patterns for a workroom were explored by computational fluid dynamics (CFD) simulations for various inlet locations, exhaust locations, contaminant gas densities, and dilution air flow rates. Average contaminant concentrations were calculated for the entire room, the breathing zone plane, and the near-source breathing zone (BZ). The computational results were validated with experimental results. For wall jet inlets and for lighter than air, the exhausts located near the ceiling resulted in lower concentrations than the corresponding exhausts near the floor. Also, the exhausts located on the same wall as the inlet were relatively better than that of the opposite side wall. The relative density of the contaminant was found to have some effects on the concentration distribution at low flow rates, whereas this effect was negligible at higher flow rates (8 ACH or higher). Exhaust location was not important for ceiling inlets as the room was well mixed. Although ceiling inlet type had almost no effect on average concentration, near-source concentrations were markedly less for the ceiling jet inlet than for the ceiling diffuser inlet.

Optimizing PEFC Stack Design and Operation for Energy and Water Balance in Transportation Systems

A simple model of a fuel-cell system is used to examine the effects of selected stack characteristics on the energy- and water-balance of the system. The results show that operating pressure, air stoichiometry, and the temperature difference between the air and coolant exhausts from the stack have major impacts on the heat-rejection requirement of the system. Interestingly, a system that utilizes a stack with an ambient exit pressure can have heat-rejection requirements comparable to a system that utilizes an elevated stack exit pressure. It is also shown that UTC Fuel Cells' technology provides a means of achieving excellent performance at low operating pressure and air stoichiometry, while maintaining the desired temperature profiles within the stack. The result is a system with high efficiency and modest heat-rejection requirements.

Homologous series of C 1–C 10 monocarboxylic acids and C 1–C 6 carbonyls in Los Angeles air and motor vehicle exhausts

Molecular distributions of monocarboxylic acids (C 1–C 10) and aldehydes (C 1–C 6) have been studied in the atmosphere of Los Angeles, as well as in motor exhaust and city dust samples. Acetic and formic acids followed by propionic acid were found to be the dominant organic acid in the gaseous phase. Formaldehyde and acetaldehyde are two dominant carbonyls, followed by propionaldehyde and glyoxal. The concentrations of organic acids and aldehydes in Los Angeles air during autumn 1984 was 0.52–5.2 and 0.94–5.8 ppb, respectively. In contrast, concentrations of the organic acids and aldehydes in motor exhaust collected under running modes were 140–410 and 340–2500 ppb, respectively. This suggests that internal combustion engines are important primary sources of both volatile organic acids and aldehydes in the urban atmosphere. By contrast, diurnal variations in concentrations of organic acids were observed during clear hot days (maximum temperature: up to 40°C), whereas such trends were largely absent during low overcast days. A positive correlation ( r=0.8) was observed between the acid concentrations and maximum ambient temperatures, suggesting that secondary photochemical production of organic acids is much more important in Los Angeles than primary emissions from automobiles during daytime under strong solar radiation.

Animal Welfare in Slaughter Plants

There are five basic causes of animal welfare problems in slaughter plants. They are: 1) Poorly designed or improper stunning and handling equipment. 2) Distractions which impede animal movement, such as sparkling reflections on a wet fioor, air hissing, high-pitched noise or air drafts blowing down the race towards approaching animals. These distractions can ruin the performance of a well designed system and cause animals to become excited. When this happens, prodding will be required to make them move. 3) Lack of employee training and poor supervision of employees by management. 4) Poor maintenance of equipment and facilities, such as malfunctioning stunners or worn, slick fioors which cause animals to slip and fall. 5) Poor condition of animals arriving at the plant, such as cripples and sick animals. Another problem is pigs and cattle from excitable genetic lines which are more likely to become agitated during handling. To maintain a high standard of welfare, all five problem areas must be addressed. A survey of 29 Canadian slaughter plants indicated that 27% had excellent non-slip fioors and 21% had slick fioors which would cause animals to slip. Twenty-four percent had high pitched motor noise or hissing air exhausts that caused animals to balk. Air drafts blowing down the race towards approaching animals were a problem in 9% of the plants. Air drafts will often impede animal movement.

TCDD receptor ligands present in extracts of urban air particulate matter induce aryl hydrocarbon hydroxylase activity and cytochrome P-450c gene expression in rat hepatoma cells

In previous studies we have shown that substances associated with particulates collected from urban air and automobile exhaust bind with high affinity to the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) receptor present in rat liver cytosol. In this study we used a rat hepatoma cell line, H4IIE, to investigate the effect of such substances on an enzyme system, aryl hydrocarbon hydroxylase (AHH), which is regulated via the TCDD receptor. The results demonstrate that AHH activity in the H4IIE cell line can be induced by extracts of particulates collected from urban air and automobile exhausts in a dose-dependent manner, and that the AHH activity is inducible by five polycyclic aromatic hydrocarbons (PAHs) including 1-/3-nitrobenzo[a]pyrene and 6-chlorochrysene, all present in extracts of particulates from urban air and automobile exhausts. The induction of AHH activity is correlated to apparent TCDD receptor affinity for investigated PAHs (r = 0.85) and particulate extracts. Biochemically, treatment of the cells with 5,6-benzoflavone significantly increased the level of cytochrome P-450c but not P-450d as shown by immunoblotting and analysis of mRNA levels. The data indicate that substances present in extracts of urban air particulates can interact with the TCDD receptor in intact cells and cause an accumulation of cytochrome P-450c mRNA leading to an increased synthesis of the gene product and thus an increase in enzyme activity.

Collecting Particles from Gin Lint Cleaner Air Exhausts

ABSTRACT MEETING strict particulate emission standards is currently a problem for the ginning industry. Small-diameter cyclones are currently used as primary collectors on gin seed-cotton system exhausts. A study was conducted to determine the effectiveness of small-diameter cyclones (1D3D design) as primary collectors on lint-cleaner exhausts. A wet scrubber was also evaluated as a secondary cleaner on the cyclone exhaust. The cyclone collectors captured an average of 90.8 per-cent by weight of exhaust particulates as a primary cleaner. The scrubber then removed an average of 73.5 percent by weight as a secondary cleaner. The combined collection efficiency of the cyclone and wet scrubber system averaged 97.6 percent. This information should be useful to the ginning industry in designing particulate collection systems to meet particulate emission stand-ards.