scholarly journals Numerical Assessment of an Air Cleaner Device under Different Working Conditions in an Indoor Environment

2021 ◽  
Vol 13 (1) ◽  
pp. 369
Author(s):  
Farshad Moradi Kashkooli ◽  
Mostafa Sefidgar ◽  
Madjid Soltani ◽  
Shahab Anbari ◽  
Seyed-Amir Shahandashti ◽  
...  
Keyword(s):  
Working Conditions ◽  
Indoor Air ◽  
Indoor Environment ◽  
Removal Rate ◽  
Operating Conditions ◽  
Exit Angle ◽  
Maximum Reduction ◽  
Numerical Assessment ◽  
Air Cleaner ◽  
Air Ejection

Transmission and spread of exhaled contaminants in the air may cause many airborne infectious diseases. In addition to appropriate ventilation, air cleaner devices are used as one of the most common ways to improve the indoor air quality. Therefore, it is necessary to understand the performance of an air cleaner under different operating conditions. This study mainly concerns investigating the effect of presence or absence of furniture and its displacement on the removal rate of the particles leaving a person’s mouth while coughing in an isolated room. Moreover, the effect of air exit angle of the device on removal rate of contaminated particles and the pattern of their dispersion within a room was studied. To this aim, computational fluid dynamics were employed to examine the mentioned effects by using the Eulerian− Lagrangian method. As the results indicated, when the furniture was placed farther away from the device, more particles were removed by the device. Additionally, the air ejection angle of the air cleaner device significantly affects the removal of particles. Results of the present study could improve use of air cleaner devices for maximum reduction of particles in the indoor environment.

scholarly journals Electrostatic Precipitators as an Indoor Air Cleaner—A Literature Review

2020 ◽  
Vol 12 (21) ◽  
pp. 8774
Author(s):  
Alireza Afshari ◽  
Lars Ekberg ◽  
Luboš Forejt ◽  
Jinhan Mo ◽  
Siamak Rahimi ◽  
...  
Keyword(s):  
Indoor Air ◽  
Indoor Environment ◽  
Indoor Environmental Quality ◽  
Air Filtration ◽  
Pressure Drops ◽  
Air Cleaning ◽  
Air Cleaner ◽  
Air Cleaners ◽  
Electrostatic Precipitators ◽  
Cleaning Technology

Many people spend most of their time in an indoor environment. A positive relationship exists between indoor environmental quality and the health, wellbeing, and productivity of occupants in buildings. The indoor environment is affected by pollutants, such as gases and particles. Pollutants can be removed from the indoor environment in various ways. Air-cleaning devices are commonly marketed as benefiting the removal of air pollutants and, consequently, improving indoor air quality. Depending on the type of cleaning technology, air cleaners may generate undesired and toxic byproducts. Different air filtration technologies, such as electrostatic precipitators (ESPs) have been introduced to the market. The ESP has been used in buildings because it can remove particles while only causing low pressure drops. Moreover, ESPs can be either in-duct or standalone units. This review aims to provide an overview of ESP use, methods for testing this product, the performance of existing ESPs concerning removing pollutants and their byproducts, and the existing market for ESPs.

scholarly journals Core Stress Analysis of Amorphous Alloy Transformer for Rail Transit under Different Working Conditions

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 164
Author(s):  
Jianwei Shao ◽  
Cuidong Xu ◽  
Ka Wai Eric Cheng
Keyword(s):  
Amorphous Alloy ◽  
Working Conditions ◽  
Short Circuit ◽  
Element Model ◽  
Operating Conditions ◽  
Iron Core ◽  
Rail Transit ◽  
Transit System ◽  
The Core ◽  
Distribution Transformers

The rail transit system is a large electric vehicle system that is strongly dependent on the energy technologies of the power system. The use of new energy-saving amorphous alloy transformers can not only reduce the loss of rail transit power, but also help alleviate the power shortage situation and electromagnetic emissions. The application of the transformer in the field of rail transit is limited by the problem that amorphous alloy is prone to debris. this paper studied the stress conditions of amorphous alloy transformer cores under different working conditions and determined that the location where the core is prone to fragmentation, which is the key problem of smoothly integrating amorphous alloy distribution transformers on rail transit power supply systems. In this study, we investigate the changes in the electromagnetic field and stress of the amorphous alloy transformer core under different operating conditions. The finite element model of an amorphous alloy transformer is established and verified. The simulation results of the magnetic field and stress of the core under different working conditions are given. The no-load current and no-load loss are simulated and compared with the actual experimental data to verify practicability of amorphous alloy transformers. The biggest influence on the iron core is the overload state and the maximum value is higher than the core stress during short circuit. The core strain caused by the side-phase short circuit is larger than the middle-phase short circuit.

Determination of cost-efficient cooling power range for improving the performance of internally cooled ultrasonic atomization liquid desiccant dehumidifiers

2020 ◽  
Vol 29 (9) ◽  
pp. 1260-1276
Author(s):  
Zili Yang ◽  
Lu-An Chen ◽  
Ruiyang Tao ◽  
Ke Zhong
Keyword(s):  
Power Efficiency ◽  
Removal Rate ◽  
Operating Conditions ◽  
Cooling Power ◽  
Internal Cooling ◽  
Liquid Desiccant ◽  
Improvement Rate ◽  
Ultrasonic Atomization ◽  
Internally Cooled ◽  
Cost Efficient

Liquid desiccant dehumidifiers (LDDs) can be improved by adding internal cooling. However, the addition of excessive cooling power may deteriorate the system‘s cost-efficiency, whereas the addition of insufficient cooling power leads to negligible performance improvements. The objective of this study is to determine the suitable cost-efficient cooling power range for improving the performance of internally cooled LDDs (IC-LDDs). A novel method and a set of criteria related to the moisture removal rate, cooling-power efficiency ( ηc) and coefficient of dehumidification performance from cooling power ( DCOPcooling) were proposed to determine cost-efficient cooling power. The internally cooled ultrasonic atomization liquid desiccant system (IC-UADS), together with a well-validated model based on the conservation laws of mass and energy and the sensible heat balance, was adopted to demonstrate the analysis. The results showed that, although the dehumidification performance improves with increasing cooling power, the improvement rate decreases, while ηcand DCOPcoolingdecline quickly (by 87.9%). For cost-efficient improvement, the necessary power proportion of internal cooling to the system‘s target dehumidification capacity tends to be stable, which was about 29% for the IC-UADS, and independent of the operating conditions. The results may help to determine the reasonable cooling power range for cost-efficient improvement of IC-LDDs.

Statistical Evaluation of Indoor Air Quality Changes after Installation of the PSD System in Seoul’s Metro

2011 ◽  
Vol 20 (1) ◽  
pp. 187-197 ◽  
Author(s):  
Min Jeong Kim ◽  
Yong Su Kim ◽  
Abtin Ataei ◽  
Jeong Tai Kim ◽  
Jung Jin Lim ◽  
...  
Keyword(s):  
Air Quality ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Operating Conditions ◽  
Indoor Environments ◽  
Multivariate System ◽  
Metro Station ◽  
Adverse Health Effects ◽  
Subway Stations ◽  
Tele Monitoring

The purpose of this study was to evaluate changes in the concentration of air pollutants in the indoor environments, which could be caused by seasonal changes or changes in operating conditions of subway metro stations. In fact, there are many different types of pollution that can cause contamination in subway stations, and changes in operating conditions can also lead to changes in the indoor air quality (IAQ). Therefore, in order to establish a proper management of IAQ, it would be necessary to evaluate the changes in IAQ according to the changes in conditions. To do this, the present study used a multivariate analysis of variance (MANOVA). The results of testing the hypothesis proved that two groups, divided by the condition of a platform screen door (PSD) system, could differ statistically. Furthermore, those multidimensional differences were caused by installation of a PSD system. When applied to a real-time tele-monitoring system, MANOVA could clearly identify the daily and weekly variations of IAQ in the subway station, as well as the PSD system’s condition. Accordingly, this method could be useful for developing a multivariate system to statistically evaluate the experimental IAQ results in order to optimise operating conditions in a subway metro station to improve IAQ, and to minimise adverse health effects on passengers by exposure to harmful substances.

scholarly journals Effects of room airflow on accurate determination of PUF-PAS sampling rates in the indoor environment

2018 ◽  
Vol 20 (5) ◽  
pp. 757-766 ◽  
Author(s):  
Nicholas J. Herkert ◽  
Keri C. Hornbuckle
Keyword(s):  
Indoor Air ◽  
Indoor Environment ◽  
Accurate Determination ◽  
Passive Samplers ◽  
Air Toxics ◽  
Precise Interpretation

Accurate and precise interpretation of concentrations from polyurethane passive samplers (PUF-PAS) is important as more studies show elevated concentrations of PCBs and other semivolatile air toxics in indoor air of schools and homes.

Study on De-Nitrification of Improved Step-Feed Progress

2014 ◽  
Vol 703 ◽  
pp. 171-174
Author(s):  
Bing Wang ◽  
Yi Xiao ◽  
Shou Hui Tong ◽  
Lan Fang ◽  
Da Hai You ◽  
...  
Keyword(s):  
Water Quality ◽  
Organic Matter ◽  
Fluidized Bed ◽  
Removal Efficiency ◽  
Nitrogen Removal ◽  
Removal Rate ◽  
Operating Conditions ◽  
Removal Mechanism ◽  
Aerobic Zone

Improved step-feed de-nitrification progress combined with biological fluidized bed was introduced in this study. The progress had good performance and capacity of de-nitrification and organic matter. The experiment result showed that the de-nitrification efficiency of the improved biological fluidized bed with step-feed process was higher than the fluidized bed A/O process under the same water quality and the operating conditions. When the influent proportion of each segment was equal, the system showed good nitrogen removal efficiency with the change of influent C/N ratio, HRT and sludge return ratio. The removal rate of TN reached up to 88.2%. It showed that the simultaneous nitrification and de-nitrification phenomenon happened in the aerobic zone. The nitrogen removal mechanism was also studied.

Computational Modeling of Particulate Pollutant Transport in a Ventilated Room in the Presence of Two Heated Breathing and Rotating Manikins

2017 ◽  
Author(s):  
Seyed Ali Keshavarz ◽  
Mazyar Salmanzadeh ◽  
Goodarz Ahmadi
Keyword(s):  
Air Quality ◽  
Computational Modeling ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Rotational Motion ◽  
Indoor Environment ◽  
Ventilation System ◽  
Thermal Plume ◽  
Displacement Ventilation ◽  
Simulation Results

Recently, attention has been given to indoor air quality due to its serious health concerns. Clearly the dispersion of pollutant is directly affected by the airflow patterns. The airflow in indoor environment is the results of a combination of several factors. In the present study, the effects of thermal plume and respiration on the indoor air quality in a ventilated cubicle were investigated using an unsteady computational modeling approach. The person-to-person contaminant transports in a ventilated room with mixing and displacement ventilation systems were studied. The effects of rotational motion of the heated manikins were also analyzed. Simulation results showed that in the cases which rotational motion was included, the human thermal plume and associated particle transport were significantly distorted. The distortion was more noticeable for the displacement ventilation system. Also it was found that the displacement ventilation system lowered the risk of person-to-person transmission in an office space in comparison with the mixing ventilation system. On the other hand the mixing system was shown to be more effective compared to the displacement ventilation in removing the particles and pollutant that entered the room through the inlet air diffuser.

A Self-Correcting and Self-Checking Gas Turbine Meter

1982 ◽  
Vol 104 (2) ◽  
pp. 143-149 ◽  
Author(s):  
W. F. Z. Lee ◽  
D. C. Blakeslee ◽  
R. V. White
Keyword(s):  
Gas Turbine ◽  
Operating Conditions ◽  
Exit Angle ◽  
Test Results ◽  
Main Rotor ◽  
Calibration Accuracy

A new metering concept of a self-correcting and self-checking turbine meter is described in which a sensor rotor downstream from the main rotor senses and responds to changes in the exit angle of the fluid leaving the main rotor. The output from the sensor rotor is then electronically combined with the output from the main rotor to produce an adjusted output which automatically and continuously corrects to original meter calibration accuracy. This takes place despite changes in retarding torques, bearing wear and/or upstream conditions occurring in field operations over those which were experienced during calibration. The ratio of the sensor rotor output to the main rotor output at operating conditions is also automatically and continuously compared with that at calibration conditions. This provides an indication of the amount of accuracy deviation from initial calibration that is being corrected by the sensor rotor. This concept is studied theoretically and experimentally. Both the theory and test results (laboratory and field) confirm the concept’s validity and practicability.

A new strategy to improve ramie degumming based on removal of the xylan branched structure

2021 ◽  
pp. 004051752110449
Author(s):  
Huihui Wang ◽  
Tong Shu ◽  
Pandeng Li ◽  
Yun Bai ◽  
Mengxiong Xiang ◽  
...  
Keyword(s):  
Removal Rate ◽  
Natural Fibers ◽  
Green Manufacturing ◽  
Operating Conditions ◽  
Ramie Fiber ◽  
Wild Type ◽  
Acetyl Xylan Esterase ◽  
Degumming Process ◽  
Main Component ◽  
Engineered Strain

Ramie fiber is known as the “king of natural fibers,” and the key to its wide application is efficient and green manufacturing. Microbial degumming has gradually become a hot area of research due to its environmental protection and mild operating conditions. However, some gummy materials remain after microbial degumming. Xylan is the main component of residual gums; its acetylated branched chains create the space barrier that makes the removal of hemicellulose difficult during ramie degumming. An acetyl xylan esterase (AXE) was obtained from Bacillus pumilus and characterized to solve this problem. Its optimum temperature and pH were 35°C and 8.0, respectively, and it had good temperature and pH stability. These properties were consistent with the conditions of ramie degumming and they laid a foundation for the application of AXE in ramie degumming. Besides, an engineered strain with a high activity of AXE was constructed successfully on the basis of the wild-type degumming strain Pectobacterium carotovorum HG-49 and used for ramie degumming. The removal rate of hemicellulose and total gums by the engineered strain increased by 4.89% and 2.53%, respectively, compared with that of the wild-type strain. Moreover, the role of this AXE in ramie degumming was further proven by X-ray diffraction and scanning electron microscopy. This study showed that AXE played an important role in the removal of hemicellulose in the degumming process of ramie fibers, thus providing a promising degumming strategy for ramie and other bast fiber plants.

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