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排序方式: 共有139条查询结果,搜索用时 15 毫秒
1.
This paper provides a synthesis of current knowledge about the associations of ventilation system types in office buildings with sick building syndrome (SBS) symptoms and discusses potential explanations for the associations. Most studies completed to date indicate that relative to natural ventilation, air conditioning, with or without humidification, was consistently associated with a statistically significant increase in the prevalence of one or more SBS symptoms, by approximately 30 to 200%. In two of three analyses from a single study (assessments), symptom prevalences were also significantly higher in air-conditioned buildings than in buildings with simple mechanical ventilation and no humidification. The available data also suggest, with less consistency, an increase in risk of symptoms with simple mechanical ventilation relative to natural ventilation. Insufficient information was available for conclusions about the potential increased risk of SBS symptoms with humidification or recirculation of return air. The statistically significant associations of mechanical ventilation and air conditioning with SBS symptoms are much more frequent than expected from chance and also not likely to be a consequence of confounding by several potential personal, job, or building-related confounders. Multiple deficiencies in HVAC system design, construction, operation, or maintenance, including some which cause pollutant emissions from HVAC systems, may contribute to the increases in symptom prevalences but other possible reasons remain unclear. 相似文献
2.
Diesel emission control system using combined process of nonthermal plasma and exhaust gas components' recirculation 总被引:1,自引:0,他引:1
A NOx aftertreatment system, using nonthermal plasma (NTP) reduction and exhaust gas components' recirculation, is investigated. A pilot-scale system is applied to a stationary diesel engine. In this system, NOx is first removed by adsorption, and subsequently, the adsorbent is regenerated by thermal desorption. NOx desorbed is reduced by using nitrogen NTP. Moreover, NOx, CO2, and water vapor recirculated into the engine intake reduce NOx. In this study, approximately 57% of the NOx of the exhaust (NOx: 240-325 ppm, flow rate = 300 NL/min) can be continuously treated for 58 h. A system energy efficiency of 120 g (NO2)/kWh is obtained. 相似文献
3.
Recirculating turbulent flow within a cavity with an inlet wall jet was examined. In steady water flow profiles were constructed with measurements taken with a Laser Dopplcr Anemometer system mounted on a traversing mechanism for two different inlet velocities. The results are presented in terms of mean velocities and turbulent kinetic energy distributions. Comparisons are then made with results obtained using a finite difference computational scheme based on the k-ε turbulence model. In general, good agreement was obtained between the computer code predictions and the experimental data. However, the agreement between measurements and the code predictions was much better for the mean velocity field as compared to the turbulent kinetic energy field. 相似文献
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6.
EGR和催化转化净化汽油车排气的试验研究 总被引:1,自引:0,他引:1
在发动机排气再循环和催化转化机理与车用汽油机排气特性研究的基础上,本文通过对车用汽油机装上EGR的催化转化装置后,在发动机台架上进行中低转速下的发动机负荷特性试验,探讨在有无EGR时对催化转化净化效果的影响。 相似文献
7.
E. Kouakou T. Salmon D. Toye P. Marchot M. Crine 《Chemical engineering science》2005,60(22):6346-6353
Based on airlift configuration, a novel circulating jet-loop submerged membrane bioreactor (JLMBR) adapted to ammonium partial oxidation has been developed. Membrane technology and combined air and water forced circulation are adopted to obtain a high biomass retention time and to achieve a separate control of mixing and aeration. This study is intended to determine how gas-liquid mass transfer is affected by operating conditions. In a first approximation, liquid was assumed to be perfectly mixed. A classical non-steady state clean water test, known as the “gas out-gas in” method, was used to determine the gas-liquid mass transfer coefficient kLa. Air and recirculated liquid superficial velocities were gradually increased from 0.013 to and 0.0056 to , respectively. Subsequently, the gas-liquid mass transfer coefficient kLa varied from 0.01 to . It appears to be influenced by the combined action of air and recirculated liquid flowrates in the range and , respectively, for air and liquid. Correlations are proposed to describe this double influence. Experiments were performed on tap water and a culture medium used for the autotrophic growth of nitrifying bacteria, respectively. Oxygen transfer appeared to be not significantly affected by the mineral salt encountered in this medium. 相似文献
8.
Soon Hyun Yoon Kyung Chun Kim Dae Seong Kim Myung Kyoon Chung 《Journal of Mechanical Science and Technology》1993,7(2):101-112
The flow field characteristics of a two-dimensional wall-attaching offset jet (WAOJ) are experimentally investigated by comparing
with those of a turbulent plane wall jet(PWJ). The mean velocity, the turbulent stresses and triple velocity correlations
are measured with a split film probe and anX wire probe. Even with the strong influence of the suction pressure field in the recirculation bubble at the lower corner,
it is found that the WAOJ in the wall jet region has a close similarity with the PWJ. Especially, the decay of maximum velocity
and the upper jet spread along the maximum velocity line of the WAOJ are virtually the same as those of the PWJ. The mean
velocity profile of the WAOJ attains similarity after the jet impingement onto the lower plate. However the profiles of second
and third-order moments of fluctuating velocities vary rapidly before the impingement and then relax very slowly to the similarity
profiles of the PWJ. 相似文献
9.
废气再循环降低汽油机NOx排放的实验研究及其微机控制系统的设计 总被引:2,自引:0,他引:2
为大幅度降低汽油机NOx排放,同时使发动机动力性,经济性,HC和CO排放及工作稳定性基本不变,采用废气再循环,导气屏组织进气涡流加快燃烧速率和多火花点火助燃措施,在EQ6100汽油机上进行试验研究。根据实验结果,制作了不同工况下最佳废气再循环率的脉谱,并以8031芯片为核心,脉谱为依据,设计出一种能付诸实用的车用发动机废气再循环控制系统。 相似文献
10.
本文讨论了用中频积累法实现低信噪比直接序列扩频信号的解扩,分析了中频积累法的基本原理以及环路设计中的若干问题。最后,给出了通过卫星信道时的实验数据。 相似文献