Pool fires under atmosphere and ventilation in steady-state burning (part II)

Two pool fire tests for solvent burning were made to obtain the burning rate and the mass loss rate from burning pans under atmosphere and ventilation in a cell. From the data, burning parameters for the Spalding's modified model reported in Part I were determined in steady-state pool burning.Part I of this paper was published in the May 1987 issue ofFire Technology. Reference: Gunji Nishio and Satoru Machida, Pool Fires under Atmosphere and Ventilation in Steady-State Burning, Part II,Fire Technology, Vol. 23, No. 3, August 1987, pp. 186–197.     

在受限和通风防火分区内对燃烧速率特性的试验研究

在核安全研究框架内对在受限和通风防火分区内油池火燃烧速率进行了试验研究。在实体火灾试验基础上，此研究为在受限和通风火灾场景下的燃烧速率机理提供了新的信息。描述了在自由条件和空气受限条件下所进行的试验，对试验装置、仪器以及火源进行了详细叙述。在相同场景（0．4m^2TPH油池火）下，对自由条件和空气受限条件的试验情况下的燃烧速率进行了对比。在空气受限情况下，燃烧速率与时间的变化曲线显示出三个不同阶段：自由条件和受限燃烧速率相同；不稳定阶段，空气受限条件下燃烧速率高于自由条件下的燃烧速率;稳定阶段。从图像分析看，不稳定阶段显示，动荡和间歇火焰大大提高了燃烧速率。介绍了通风速率和油池面积对此现象的影响。试验结果为理解有限区域内燃烧速率提供了新的试验信息。     

Studies on buoyancy driven two-directional smoke flow layering length with combination of point extraction and longitudinal ventilation in tunnel fires

This paper investigates the buoyancy-driven smoke flow layering length (both upstream and downstream) beneath the ceiling with combination of point extraction and longitudinal ventilation in tunnel fires. A theoretical model is developed based on previous back-laying model with only longitudinal ventilation, with modified actual heat release rate, as well as modified upstream and downstream opposing longitudinal air flow velocities by the induced flow velocity due to point extraction. Experiments are carried out in a reduced scale model tunnel with dimensionless of 72 m×1.5 m×1.3 m. A LPG porous gas burner is used as fire source. The smoke flow layering length both upstream and downstream are identified based on temperature profiles measured along the ceiling, for different experiment conditions. CFD simulations with FDS are also performed for the same scenarios. Results show that with combination of point extraction and longitudinal ventilation, the smoke flow layering length is not symmetric where it is longer downstream than that upstream. The upstream smoke layering length decreases, while the downstream layering length increases with increase in longitudinal ventilation velocity; and they both decrease with increase in point extraction velocity. The predictions by the proposed theoretical model agree well with the measurements and simulation results.     

建筑环境设计模拟分析软件DeST第8讲自然通风与机械通风系统的联合模拟分析

建筑通风对建筑环境的影响是直接而迅速的,因此对建筑热环境的模拟必须解决建筑通风的模拟问题。建筑的通风包括自然通风和机械通风,二者本质相同并且经常是同时发生的,计算时应该一起考虑,而不是分离开来。详细介绍了建筑热环境模拟软件DeST中根据多区域网络模型和管道流体网络模型发展出来的建筑通风的统一的网络模型,介绍其求解方法,并给出了建筑中常见的通风支路阻力模型,实现了建筑热环境和自然通风真正的耦合模拟。通过介绍几个利用通风模拟来分析解决设计中问题的实例,指出了建筑通风模拟的应用范围和实际意义。     

Evaluating emergency ventilation strategies under different contaminant source locations and evacuation modes by efficiency factor of contaminant source (EFCS)

Emergency ventilation plays an important role in protecting occupants when a hazardous contaminant is released indoors. A number of studies have been conducted to better understand how to protect indoor occupants with effective ventilation strategies. However, little attention has been paid to the impact of the non-uniform and time-dependent distribution of occupants during evacuation. A new concept, Efficiency Factor of Contaminant Source (EFCS), has recently been proposed to evaluate the performance of emergency ventilation by comprehensively considering the spatial and temporal distributions of both the contaminant and occupants. This paper aims to: (1) propose and demonstrate a procedure for determining an optimal ventilation strategy by using EFCS; (2) examine the effects of source locations, ventilation modes, and evacuation modes on the performance of emergency ventilation. One hundred cases with ten ventilation modes, two evacuation modes, and five source locations were investigated numerically. The results show that the EFCS concept can provide a reasonable way to evaluate the performance of emergency ventilation. The threats of different source locations may vary over a large range, and certain measures should be taken to monitor and prevent the releases at high threat locations. A system equipped with multiple ventilation modes is necessary since no universal ventilation mode can successfully mitigate all hazardous situations. The effects of an evacuation mode may be more significant than that of a ventilation mode under certain situations.     

民用建筑通风空调系统防火(烟)阀的设置

针对民用建筑防火(烟)阀的设计,对照有关规范．指出了容易被忽视的问题,提出了具体的改进措施和建议。     

多股等羽流的速度与流量修正及其对高大空间自然通风的影响

根据动量叠加原理对多股等羽流的相互作用进行了研究,定义了三个速度修正系数和流量修正系数。通过数值计算,分析了平均速度修正系数、流量修正系数随高度和热源间距的变化规律。将相互作用的多股等羽流应用于一种高大空间二区自然通风模型,计算结果显示多股等羽流的相互作用提高了热分层高度,增加了通风量,对高大空间自然通风的影响十分明显。     

国内外蒸发冷却空调技术研究进展(1)

介绍了直接蒸发冷却器的研究情况,主要包括填料的传热传质性能、净化性能及直接蒸发冷却器的应用。     

空调节能技术和措施的辨识(2)——地板送风系统设计中的困惑(上)

通过文献阅读、实验研究、工程调查,分析了现行的地板送风系统负荷计算和送风量确定过程中存在的主要问题。实验室实验和工程实践结果表明:在国内采用地板送风系统的一般办公室中,很难形成空气分层,分层与否影响空调送风量,而送风量又决定了空气是否分层;地板送风系统的负荷和送风量计算与顶送风常规空调系统并无本质区别,考虑到人体舒适感,地板送风系统的送风温度更高,送风量一般明显大于顶送风常规空调系统。空调负荷和送风量计算是地板送风系统设计中的关键,其正确与否,不但影响系统的经济性,而且还会影响系统的可行性,有必要进行深入的研究、分析和探讨。     

Biomarker versus environmental factors: seasonal variations and modelling multixenobiotic defence (MXD) transport activity in transplanted zebra mussels

The occurrence of biomarker temporal variations linked to environmental factors makes it difficult to distinguish the specific effect of pollution. The present work aims to investigate the seasonal variations of the transport activity of the multixenobiotic defence (MXD), which is used as a biological tool for the monitoring of pollution in aquatic ecosystems. The MXD transport activity was monitored monthly from August 2001 to October 2002 in zebra mussels (Dreissena polymorpha) transplanted to three sites in the Moselle River. The 'efflux method' was used to evaluate functional activity of MXD by assessing rhodamine B efflux with or without an inhibitor (verapamil). Environmental parameters were provided by a French regulatory agency (Water Agency) that monitors river water quality. The results of a principal components analysis describe the seasonal cycle of water characteristics and demonstrate that MXD activity is subjected to significant temporal variations. These data were described with a generalised linear model that enables it to link MXD variability to the seasonal variations of environmental parameters such as temperature or levels of organic contamination. This work proposes a modelling approach and highlights that the occurrence of seasonal variations in MXD response has to be taken into account in the interpretation of in situ monitoring studies.