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1.
《International Journal of Hydrogen Energy》2022,47(57):24107-24118
Vehicle fires in the tunnel are a great threat to the safe operation of the tunnel. Due to the rapid development of the hydrogen economy, the fire due to the hydrogen leakage could not be avoided and may bring great damage to the passengers and infrastructure. Due to the large difference between pool fires of traditional fossil-fueled and jet fires of hydrogen-powered vehicles, it is in doubt whether the existing longitudinal ventilation design could still be effective for the safety issue of hydrogen powered vehicles. To solve this problem, it is necessary to compare temperature characteristics of hydrogen-powered and traditional vehicle fires with and without longitudinal ventilations. In present work, we conducted a numerical investigation to discuss the different temperature distributions of traditional and hydrogen-fueled vehicle fires. Results indicate that the high temperature zone of the pool fire only exists above the ceiling of the vehicle. For hydrogen-powered vehicle fire, the high-speed hydrogen jet with the strong inertial force could push the hot smoke flows back to the ground. The ceiling temperature of hydrogen-powered vehicle fire is larger since hydrogen-powered vehicle has a larger heat release rate and the fire hazard of jet fires bring more danger compared with the pool fire. Although the temperature stratification is also obvious for the hydrogen-powered vehicle fire, the air temperature in the lower region could be heated and still high enough to bring a great damage to the passengers’ lives. This is quite different with the traditional pool fire. In addition, the critical ventilation velocity is also discussed. The theoretical equation could well predicted the critical ventilation velocity of traditional vehicle fires. For hydrogen-powered vehicle fires, the critical ventilation velocity could reach up to 6 m/s. The theoretical equation could not well predict the critical ventilation velocity of hydrogen-powered vehicle fires due to exist of hydrogen jet fires. 相似文献
2.
大豆预处理车间的粉尘分为干式粉尘和湿式粉尘。粉尘易引起设备故障和车间污染,在限定空间和条件下会发生粉尘阴燃、起火甚至爆炸,给安全生产带来隐患。针对这些问题,根据大豆预处理工艺和设备的特点设计除尘风网和工艺风网。对大豆预处理车间的除尘风网和工艺风网进行了介绍。为减少含尘气体排放,除尘风网采取循环风设计,对可能出现阴燃、起火的溜管、弯头、设备的下料接管积尘处,以及可能出现粉尘爆炸的筒仓进行防燃、防爆和抑爆处理。通过对4 000 t/d 大豆压榨厂含尘气体排放实测表明,预处理车间的风网运行稳定,实现了安全和清洁生产。 相似文献
3.
屯兰煤矿是煤与瓦斯突出矿井,瓦斯涌出量大,上隅角瓦斯治理困难。为解决这一通风难题,该矿采取沿空留巷抽采措施进行作业。实践证明,该技术解决了上隅角瓦斯积聚隐患,保障了矿井高产高效。 相似文献
4.
5.
Chester J. Lau Max Loebel Roson Keifer M. Klimchuk Tania Gautam Boyang Zhao Ran Zhao 《Indoor air》2021,31(3):769-782
Household humidification is widely practiced to combat dry indoor air. While the benefits of household humidification are widely perceived, its implications to the indoor air have not been critically appraised. In particular, ultrasonic humidifiers are known to generate fine particulate matter (PM). In this study, we first conducted laboratory experiments to investigate the size, quantity, and chemical composition of PM generated by an ultrasonic humidifier. The mass of PM generated showed a correlation with the total alkalinity of charge water, suggesting that CaCO3 is likely making a major contribution to PM. Ion chromatography analysis revealed a large amount of SO42− in PM, representing a previously unrecognized indoor source. Preliminary results of organic compounds being present in humidifier PM are also presented. A whole-house experiment was further conducted at an actual residential house, with five low-cost sensors (AirBeam) monitoring PM in real time. Operation of a single ultrasonic humidifier resulted in PM2.5 concentrations up to hundreds of μg m−3, and its influence extended across the entire household. The transport and loss of PM2.5 depended on the rate of air circulation and ventilation. This study emphasizes the need to further investigate the impact of humidifier operation, both on human health and on the indoor atmospheric chemistry, for example, partitioning of acidic and basic compounds. 相似文献
6.
Jodelle Degois Marc Veillette Patrick Poulin Benoit Lévesque Daniel Aubin Boualem Ouazia Mario Brisson François Maltais Caroline Duchaine 《Indoor air》2021,31(6):2213-2225
Indoor air quality is a major issue for public health, particularly in northern communities. In this extreme environment, adequate ventilation is crucial to provide a healthier indoor environment, especially in airtight dwellings. The main objective of the study is to assess the impact of ventilation systems and their optimization on microbial communities in bioaerosols and dust in 54 dwellings in Nunavik. Dwellings with three ventilation strategies (without mechanical ventilators, with heat recovery ventilators, and with energy recovery ventilators) were investigated before and after optimization of the ventilation systems. Indoor environmental conditions (temperature, relative humidity) and microbiological parameters (total bacteria, Aspergillus/Penicillium, endotoxin, and microbial biodiversity) were measured. Dust samples were collected in closed face cassettes with a polycarbonate filter using a micro-vacuum while a volume of 20 m3 of bioaerosols were collected on filters using a SASS3100 (airflow of 300 L/min). In bioaerosols, the median number of copies was 4.01 × 103 copies/m3 of air for total bacteria and 1.45 × 101 copies/m3 for Aspergillus/Penicillium. Median concentrations were 5.13 × 104 copies/mg of dust, 5.07 × 101 copies/mg, 9.98 EU/mg for total bacteria, Aspergillus/Penicillium and endotoxin concentrations, respectively. The main microorganisms were associated with human occupancy such as skin-related bacteria or yeasts, regardless of the type of ventilation. 相似文献
7.
The emission rate of carbon dioxide (CO2) depends on many factors but mainly on the activity level (metabolic rate) of occupants. In this study, we examined two other factors that may influence the CO2 emission rate, namely the background CO2 concentration and the indoor temperature. Six male volunteers sat one by one in a 1.7 m3 chamber for 2.5 h and performed light office-type work under five different conditions with two temperature levels (23 vs. 28°C) and three background concentrations of CO2 (800 vs. 1400 vs. 3000 ppm). Background CO2 levels were increased either by dosing CO2 from a cylinder or by reducing the outdoor air supply rate. Physiological responses to warmth, added CO2, and bioeffluents were monitored. The rate of CO2 emission was estimated using a mass-balance equation. The results indicate a higher CO2 emission rate at the higher temperature, at which the subjects were warm, and a lower emission rate in all conditions in which the background CO2 concentration increased. Physiological measurements partially explained the present results but more measurements are needed. 相似文献
8.
Kasper Kristensen David M. Lunderberg Yingjun Liu Pawel K. Misztal Yilin Tian Caleb Arata William W Nazaroff Allen H. Goldstein 《Indoor air》2019,29(4):645-655
Semivolatile organic compounds (SVOCs) emitted from building materials, consumer products, and occupant activities alter the composition of air in residences where people spend most of their time. Exposures to specific SVOCs potentially pose risks to human health. However, little is known about the chemical complexity, total burden, and dynamic behavior of SVOCs in residential environments. Furthermore, little is known about the influence of human occupancy on the emissions and fates of SVOCs in residential air. Here, we present the first‐ever hourly measurements of airborne SVOCs in a residence during normal occupancy. We employ state‐of‐the‐art semivolatile thermal‐desorption aerosol gas chromatography (SV‐TAG). Indoor air is shown consistently to contain much higher levels of SVOCs than outdoors, in terms of both abundance and chemical complexity. Time‐series data are characterized by temperature‐dependent elevated background levels for a broad suite of chemicals, underlining the importance of continuous emissions from static indoor sources. Substantial increases in SVOC concentrations were associated with episodic occupant activities, especially cooking and cleaning. The number of occupants within the residence showed little influence on the total airborne SVOC concentration. Enhanced ventilation was effective in reducing SVOCs in indoor air, but only temporarily; SVOCs recovered to previous levels within hours. 相似文献
9.
Window opening and closing is the most preferred behavior for occupants to control their indoor environment in homes. This study aims to identify driving forces for window opening and closing behavior in the home. The additional field survey was carried out for the cooling period after following the previous study. The state of windows and environmental variables for outdoor and indoor were continuously monitored in 23 sample homes over one year. The monitored data provide evidence that there is a statistically significant relationship between window opening behavior and outdoor temperature. The behavior of the occupant's manual control of windows can be described by seasonal effects, occupancy, and time of day. Indoor stimuli, such as such as temperature, humidity, and CO2, can better account for the window opening behavior than can outdoor stimuli. There are clear differences in driving variables between window opening and closing behavior. The closing behavior is better described when the outdoor and indoor variables are combined. Finally, multivariate logistic regression models were developed to predict typical patterns of window opening and closing as a function of indoor and outdoor variables. 相似文献
10.
Prof. Dr.‐Ing. Falk Jaeger 《Mauerwerk》2019,23(1):50-54
Brick masonry is not only a question of building physics, building construction and durability, i.e. sustainability, but has much to do with aesthetics and making sense, which may have been forgotten in modern architecture with its absolute lack of décor. Masonry as an art form has been scarce since the era of brick expressionism. Recently, there have been some exceptions – and thoroughly welcome. The ”Fjordenhus“ in Vejle, Denmark, is an astonishing example. 相似文献