阻燃剂对棉布和地毯热解燃烧性能的影响研究

研究了氢氧化铝和三聚氰胺氰尿酸盐对棉布和地毯热解和燃烧行为,考察了阻燃剂添加量对棉布和地毯点燃时间、热解速度和火焰持续时间的影响,并利用锥形量热仪测定了添加阻燃剂前后材料在点燃时间、热释放速率、质量损失速率和CO释放速率的变化,结果表明海水中添加10%的Al(OH)3和MCA可显著降低棉布和地毯的热解速度及热释放速率.     

Importance of accounting for the piping system and boundary conditions in determining the maximum surge pressure following heat-exchanger tube-rupture

Shell-tube type heat exchangers are often used to exchange heat between a high-pressure fluid and a low-pressure fluid, and the pressure difference between the two fluids could be significantly high. If the difference in the design pressure between the low-pressure (LP) and high-pressure sides is greater than that covered by American Petroleum Institute (API 520 and 521) 10/13^th rule, dynamic analysis is required to ascertain that the maximum surge pressure that could be reached does not compromise the integrity of the LP side of the exchanger. API guidelines also notes that attention should also be given not only to the shell-side of the heat exchanger under evaluation, but also to the “upstream and downstream systems” This paper offers further insight into the importance of including the surrounding piping systems around the subject heat-exchanger where a tube-rupture scenario is considered, and also directs attention to the importance of correctly specifying the appropriate boundary conditions (B.C.) at the far ends of both the upstream and downstream piping systems. It demonstrates the effects of specifying different B.C. on the maximum pressure surge via a case study of a hot separator vapour condenser in a bitumen hydrotreating unit, where the process fluid on the tube-side is a vapour–liquid mixture at 9660 kPa(g). The vapour mass fraction of the process fluid is approximately 0.5, and is mostly hydrogen. The fluid on the LP side is cooling water connected to the plant supply and return cooling systems as well as another adjacent low pressure condenser. The design pressure for the cooling water piping system and the adjacent condenser is 1380 kPa(g).     

特大断面公路隧道线型感温火灾探测系统适用性研究

随着我国公路交通量日益增多,大断面、特大断面公路隧道不断涌现,可靠、有效的隧道火灾探测越来越重要。选取了6种典型的隧道断面,综合考虑探测器类型、纵向风速、火源功率、火源位置等因素,运用火灾动力学模拟软件FDS分析了系列火灾场景下温度、烟气分布、探测器报警时间、报警位置偏移量等特性。研究结果表明: 隧道断面尺寸、纵向风速越大,感温探测器报警时间越长。通过对顶棚烟气温度的分析,发现特大断面隧道中线型感温探测系统采用差温报警较定温报警更有效。在使用差温报警时,纵向通风会使报警位置发生偏移,报警位置偏移量d与隧道纵向风速v、火源到隧道顶棚距离Hd满足线性关系式:d=6.404v+0.923Hd-6.762。随着隧道断面尺寸的增大,需要敷设更多的感温光纤以在规定时间(60 s)内探测到火灾。对于高度H≥12 m的隧道,即使增设多条感温光纤,也无法在60 s内有效报警,需补充设置基于火焰和烟气特征的非接触式火灾探测器。     

The main and added effects of heat on mortality in 33 Chinese cities from 2007 to 2013

● The main and added effect from heat co-existed in China. ● Both of the main and added effect could increase the mortality risk of population. ● Females, the elderly, the less educated and inland residents were more vulnerable. Increases in ambient temperatures and the frequency of extreme heat events constitute important burdens on global public health. However, evidence on their effects on public health is limited and inconclusive in China. In this study, data on daily deaths recorded in 33 Chinese cities from 2007 to 2013 was used to evaluate the effect of heat on mortality in China. In addition to the definition of a heatwave established by the China Meteorological Administration, we combined four city-specific relative thresholds (90th, 92.5th, 95th, and 97.5th percentiles) of the daily mean temperature during the study period and three durations of ≥ 2, ≥ 3, and ≥ 4 days, from which 13 heatwave definitions were developed. Then, we estimated the main and added effects of heat at the city level using a quasi-Poisson generalized additive model combined with a distributed lag nonlinear model. Next, the estimates for the effects were pooled at the national level using a multivariable meta-analysis. Subgroup analysis was performed according to sex, age, educational attainment, and spatially stratified heterogeneity. The results showed that the mortality risk increased from 22.3% to 37.1% due to the effects of the different heatwave definitions. The added effects were much lower, with the highest increase of 3.9% (95% CI: 1.7%–6.1%) in mortality risk. Females, the elderly, populations with low educational levels, and populations living inland in China were found to be the most vulnerable to the detrimental effects of heat. These findings have important implications for the improvement of early warning systems for heatwaves.     

密度对聚氨酯软泡收缩及燃烧行为的影响

采用锥形量热仪研究不同密度聚氨酯软泡(FPUF)的燃烧行为,并根据摄像、体视显微镜所观察的样品形体及泡孔结构的变化来研究火灾条件下FPUF的收缩特性。研究结果表明,收缩是表层泡孔受热发生热解生成焦油所致的泡孔塌缩现象,焦油层下方泡孔结构基本没有变化;FPUF密度越大着火前的收缩速率越小,同一时刻表层泡孔热解生成的焦油层越薄。FPUF的着火燃烧可分为受热收缩、燃烧收缩和池火燃烧三个阶段。中高密度样品HRR曲线先出现平台后出现峰值,分别对应于燃烧收缩和池火阶段,且密度越大HRR曲线的平台越低、峰值越高,燃烧收缩阶段的FIGRA越小,而池火燃烧阶段的FIGRA越大。着火前的快速收缩导致低密度样品的HRR曲线不出现平台只呈现单峰。     

基于锥形量热仪的几种防火布燃烧性能研究

生产企业常在电缆或者贵重高危机器处设置防火布来保护生产设备设施的消防安全,选取五种常用的防火布:石棉纤维防火布、陶瓷纤维防火布、硅胶防火布、涂胶防火布、碳素纤维防火布,通过锥形量热仪实验研究不同辐射强度对防火布燃烧性能的影响。结果表明:点燃时间的均方根倒数与辐射强度之间呈现线性关系;在35 kW/m~2辐射强度工况下,碳素纤维防火布的热释放速率最大,达到272.59 kW/m~2,有效燃烧热的峰值也最大,达到529.52 kJ/g;综合比较各样品的燃烧性能,防火能力强弱顺序为:硅胶防火布石棉纤维防火布陶瓷纤维防火布碳素纤维防火布涂胶防火布。     

西藏高原地区浮力羽流温升特性研究

通过在拉萨对不同尺寸的三种油池火试样分别进行试验,获取了柴油在相当于平原地区64%大气压力和氧浓度条件下不同工况下不同位置处羽流中心线温度的实时变化情况等原始数据,计算了不同尺寸油池火的热释放速率,分析了低氧低压环境下的羽流中心温升特点及原因,并将实验值与经典羽流模型Heskestad模型的计算值进行了比较,分析了传统羽流模型在高原地区的适用性.     

高影响天气对苏州市大气污染物特征的影响

利用苏州市2010—2012年大气污染物逐时质量浓度数据和气象条件资料,分析4类高影响天气对该市大气污染物扩散的影响。研究表明:暴雨对污染物的清除作用主要与降水时间和强度等因子有关,且降水时间的影响大于降水强度;夏季高温日污染物平均质量浓度高于非高温日,PM10、PM2.5、O3、NO2分别增长了29.5%、19.2%、51.3%和13.5%,且O3质量浓度大于321.6μg/m3的日最高气温均在33℃以上;寒潮过境对污染物有很好的清除效应,可对不同污染物影响程度不同;台风带来的大风和降雨能使污染物浓度迅速降低,其来临前的外围下沉气流可能对污染物浓度升高有影响。     

沈阳世园会玫瑰园环保型能源系统的应用

沈阳世园会玫瑰园采用环保型能源系统-土壤源热泵系统,该系统为清洁能源,节能高效,无废气、废水、废弃物排放,不会对环境造成污染,该系统符合国家能源发展趋势也符合国家能源利用政策。     

Comparison of PCE and TCE disappearance in heated volatile organic analysis vials and flame-sealed ampules

The rates of hydrolysis reported for tetrachloroethylene (PCE) and trichloroethylene (TCE) at elevated temperatures range over two orders-of-magnitude, where some of the variability may be due to the presence of a gas phase. Recent studies suggest that volatile organic analysis (VOA) vials provide a low-cost and readily available zero headspace system for measuring aqueous-phase hydrolysis rates. This work involved measuring rates of PCE and TCE disappearance and the corresponding appearance of dechlorination products in water-filled VOA vials and flame-sealed ampules incubated at 21 and 55 °C for up to 95.5 days. While PCE and TCE concentrations readily decreased in the VOA vials to yield first-order half lives of 11.2 days for PCE and 21.1 days for TCE at 55 °C, concentrations of anticipated dechlorination products, including chloride, remained constant or were not detected. The rate of PCE disappearance was 34 times faster in VOA vials at 55 °C compared to values obtained with flame-sealed ampules containing PCE-contaminated water. In addition, the concentration of TCE increased slightly in flame-sealed ampules incubated at 55 °C, while a decrease in TCE levels was observed in the VOA vials. The observed losses of PCE and TCE in the VOA vials were attributed to diffusion and sorption in the septa, rather than to dechlorination. These findings demonstrate that VOA vials are not suitable for measuring rates of volatile organic compound hydrolysis at elevated temperatures.