基于FDS的地下车库补风口数量及相对位置设置优化研究

文中从烟气控制角度出发,将火源上方平均温度、疏散走道烟气层厚度、1.8m处空间内温度和能见度4个指标作为判断不同补风口数量和补风口相对位置对地下车库火灾的影响,结果表明,在安全经济和满足规范要求的基础上,应先考虑将补风口设置为1个,当设置为1个超过规范对补风口风速要求时,应将补风口设置在长边中心位置以达到更好的效果,为地下车库补风系统设计和优化提供参考。     

消防楼梯间前室设常开百叶风口的分析

1 概述 随着社会经济的发展,高层建筑越来越多,防排烟设计已得到众多设计人员的重视,但对设置机械加压送风系统的消防楼梯间前室的风口方式存在着许多不同的观点,本文拟对前室设置一般常开百叶风口作一定量分析。 目前高层建筑前室正压送风系统的风口设置大致有以下四种方式,即:①前室送风口为电动风口,平时均严密关闭,发生火灾时,只开启着火层前室的风口。②前室送风口为电动风口,平时均严密关闭,发生火灾时,自动开启着火层及     

超低能耗居住建筑厨房补风口位置模拟研究

研究超低能耗居住建筑厨房的室内气流组织,采用ANSYS软件对该类建筑厨房自然补风口的不同位置进行模拟,得出吊顶设置下送补风口的最佳位置应在人员烹饪活动范围正上方.结合装修设置侧送补风口与排油烟机的排风口底平,以及侧送补风口开设在橱柜侧面的形式,均可改善烹饪活动范围的气流组织,但与补风口相对的位置存在吹风感.     

超低能耗居住建筑卧室室内环境模拟研究

以超低能耗居住建筑卧室为研究对象,采用ANSYS软件对卧室新风口的不同形式及与空调风口之间的位置关系进行模拟分析,结果表明在空调风口附近设置顶部侧送新风口,其室内的气流组织优于下送散流器新风口;顶部俱侧送百叶新风口与空调风口间距不宜过大;在空调风口附近布置下送散流器新风口时,风口宜尽量靠近空调回风口.     

皮带转运点密闭罩下部空间及吸风口数值模拟

对于目前皮带转运点密闭罩扬尘控制效果不佳的问题,利用CFD数值模拟方法对密闭罩未安装下部空间时的卸料扬尘进行分析,根据气流组织设计密闭罩下部空间;通过对该空间不同位置单吸风口的粉尘捕集效果进行对比,分析得到单吸风口设置对扬尘控制效果不利;优化设计吸风口位置,采用双吸风口设置使捕集效率达到100%。     

高层建筑防排烟系统加压送风量计算的探讨

论述了高层建筑设置防排烟系统的重要性,分析了不同形式前室加压送风口的特点,提出了风口形式不同时,楼梯间及前室分别设置加压送风系统所需的加压送风量的计算公式.     

医院输液室风口设置和室内布局对气流组织影响的研究

通过数值模拟研究了不同风口设置及室内布局情况下,医院输液室内的气流组织和病人散发的带菌颗粒物的运动分布特征。结果表明,不同挡板高度对气流组织的影响较大,尤其对人员附近局部区域的空气品质和污染物扩散方式有一定的影响。结合医院输液室室内布局的实际情况,对风口处气流组织进行了分析,并提出了合理的风口设计方案。     

特别策划

《公共场所集中空调通风系统卫生管理办法》要点卫生部2006年2月10日制定2006年3月1日起实施1.对新风及风口的要求集中空调通风系统的新风应当直接来自室外,严禁从机房、楼道及天棚吊顶等处间接吸取新风。新风口应当远离建筑物的排风口、开放式冷却塔和其他污染源,并设置防护网和初效过滤器。送风口和回风口应当设置防鼠装置,并定期清洗,保持风口表面清洁。     

空调百叶风口防风雨性能的测试分析

为了解空调百叶风口在台风暴雨气象条件下的防风雨性能,对普通型和防雨型百叶风口的防风雨性能进行了实测研究。结果表明:普通单层固定百叶风口只能抵御不超过4级风造成的风雨袭击,防雨百叶风口具有较好的防雨性能,但也难以抵御7级以上风造成的风雨袭击,因此设置防雨百叶风口并不是抵御台风暴雨侵袭的一种有效措施。     

方形吸顶散流器阻力特性实验研究

设计了空气分布器性能实验室,实测了不同尺寸方形吸顶散流器在等温工况下不同喉部风速时的静压损失和局部阻力系数。结果表明:方形吸顶散流器风口的阻力系数主要与风口的尺寸和结构相关,而风速对其影响不大;不同风速下散流器风口的平均阻力系数与风口喉部尺寸呈良好的线性关系,风口喉部尺寸越大,阻力系数越小。通过实验数据拟合得到了风口阻力系数与方形吸顶散流器喉部尺寸的理论计算关系式。     

Buoyancy and inertial force on oscillations of thermal-induced convective flow across a vent

Natural vents are commonly installed in buildings for smoke control. Air motion is induced by buoyancy of the thermal sources inside the building. Hot smoke is expected to be exhausted out of the vent. However, directions of air flowing across the vent might be oscillating under some conditions. The ratio B of buoyancy to inertial force defined by the Grashof number over the square of the Reynolds number is the key parameter in determining airflow oscillations.     

Thermal analysis of an electric power transformer inside an enclosure – a case study

Electric transformer inside an enclosure is used in the medium power transmission lines. It reduces the power losses more than other transformers in the transmission lines. In this study, thermal performance of a transformer inside an enclosure was investigated numerically and experimentally under different operating conditions. The experimental data were collected while the transformer was working in real operating conditions. The 3D numerical analysis was conducted and then verified with the experimental data. The results of this study show that despite lower power loss of the transformer, compared to the conventional transformers which are commonly installed on the overhead power line towers, the enclosure of the transformer has a serious problem of poor ventilation and it causes the transformer to run at higher temperature condition and this consequently decreases the transformer's efficiency. However, this problem can be fixed by implementing some changes in the enclosure's air vents and also by adding a fan on the roof of the enclosure.     

On the transition from displacement to mixing ventilation with a localized heat source

We investigate the steady state natural ventilation of a room heated at the base and consisting of two vents at different levels. We explore how the air flow rate and internal temperature relative to the exterior vary as a function of the vent areas, position of the vents and heat load in order to establish appropriate ventilation strategies for a room. When the room is heated by a distributed source, the room becomes well mixed and the steady state ventilation rate depends on the heating rate, the area of the vents and the distance between the lower and upper level vents. However, when the room is heated by a localised source the room becomes stratified. If the effective ventilation area is sufficiently large, then the interface separating the two layers lies above the inlet vent and the lower layer is comprised of ambient fluid. In this case the upper layer is warmer than in the well mixed case and the ventilation rate is smaller. However, if the effective area for ventilation is sufficiently small, then the interface separating the two layers lies below the inlet vent and the lower layer is comprised of warm fluid which originates as the cold incoming fluid mixes during descent from the vent through the upper layer. In this case both the ventilation rate and the upper layer temperature are the same as in the case of a distributed heat load. As the vertical separation between lower and upper level vents decreases, then the temperature difference between the layers falls to zero and the room becomes approximately well mixed. These findings suggest how the appropriate ventilation strategy for a room can be varied depending on the exterior temperature, with mixing ventilation more suitable for winter conditions and displacement ventilation for warmer external temperatures.     

Numerical simulation of the spread of smoke in an atrium under fire scenario

The Fire Dynamics Simulator code is used to investigate the smoke movement in an atrium under fire scenario. At first, by comparing with experimental data of the atrium fire under low and high heat release rates, reasonable model constants of C_s and Pr_t and appropriate grid system are determined for simulating smoke movement in the atrium, the simulation results are in good agreement with those experimental data. Then, the performance of different smoke exhaust methods in the atrium is studied. Smoke filling processes are investigated under different natural and enhanced smoke exhaust methods. Simulated results show that natural smoke exhaust method is preferred when the smoke exhaust vents are located at the ceiling of the atrium. On the other hand, when the smoke exhaust vents are located on the walls of the atrium, the higher positions of the smoke exhaust vents are preferred. In addition, the influence of the fire source locations on the smoke spreading process is presented in this paper, three kinds of fire source locations are studied, they are central fire, side wall fire and corner fire. Results indicate that the descending process of the smoke layer is the slowest when the fire source is at the corner of the atrium.     

Interaction of Sprinklers with Smoke and Heat Vents

There has been an ongoing controversy about the use of sprinklers and smoke/heat vents together, and dozens of position papers have been published over the decades. This paper reviews 13 experimental studies that have some relevance to the claims posed for and against the combined use of sprinklers and smoke/heat vents. These studies are used to evaluate the positive and negative claims that have been made with regard to the combined use of sprinklers and smoke/heat vents. Three of the studies investigate the use of smoke/heat vents alone. Four investigations include sprinklers, but do not include roof vents. Three of these are test series in which perimeter vents were used in the test facility, and the fourth included sprinklers, a partial draft curtain, and no smoke/heat vents. Four test series included sprinklers, smoke/heat vents, and draft curtains, but utilized spray or pool fires which were not subject to extinguishment by the sprinklers. Four test series included sprinklers, smoke/heat vents, draft curtains, and used Class A fuels which were subject to extinguishment.The studies of smoke and heat venting used in conjunction with sprinklers show clearly that venting does not have a negative effect on sprinkler performance. Experimental studies have shown that venting does limit the spread of products of combustion by releasing them from the building within the curtained compartment of fire origin. This improves visibility for building occupants and firefighters who need to find the seat of the fire to complete fire extinguishment. Limiting the spread of smoke and heat also reduces smoke and heat damage to the building. In the event that sprinklers do not operate, venting remains a valuable aid to manual control of the fire.The experimental studies have shown that early vent activation has no detrimental effects on sprinkler performance and have also shown that current design practices are likely to limit the number of vents operated to one and vents may in fact not operate at all in very successful sprinkler operations. Design practices should move to methods that assure early operation of vents, and vent operation should be ganged so that the benefit of roof vents is fully realized. Sprinkler design with vents and draft curtains needs to take full account of draft curtains as obstructions. Curtains should be placed in aisles rather than over storage.     

大连地区特隆布墙夏季不同降温方式的实验研究

对比分析了五种方案下墙体的温度场和得热量,确定了较为合理的特隆布墙夏季运行方案,即卷帘白天放下、夜间开启,外通风口全天开启,内通风口自动启闭。与对比房的比较结果表明采用该方案不仅有效解决了特隆布墙夏季过热问题,而且还可以对室内进行一定程度的被动式降温。针对实际应用,提出了进一步强化特隆布墙降温效果的措施。     

On the natural ventilation of two independently heated spaces connected by a low-level opening

We study the buoyancy-driven natural ventilation of two spaces which are connected to one another by a low-level opening, and each of which is connected to the exterior through a high-level vent. Each space is heated uniformly by an independent source, which provides buoyancy driving the ventilation. Using laboratory experiments, we show that these conditions lead to each space becoming well mixed at steady state. In this regime, a net flow from one space to the other is driven by the buoyancy created in the downstream space. Although it is possible in theory for the flow to develop in either direction, our new experiments and theoretical model show that, in reality, if the vents of the two spaces are at the same height, then the actual flow regime will depend primarily on the relative strength of the heat loads. If the two heat loads are sufficiently different, only the flow from the weakly heated space to the strongly heated one is stable. If the two heat loads are comparable, both modes are stable, leading to multiple flow regimes. The problem is generalised to show that, if the heights of the vents are equal, then the flow regime will depend on the relative height of the vents, as well as the relative strength of the heat loads. There is a range of combinations of vent heights and heat loads that still allow multiple flow regimes. We identify the limits of each regime and outline principles for control.     

地下车库自然通风数值模拟分析研究——以四川阆中某车库工程为例

该文以四川阆中某车库工程为对象,通过在车库顶部设置自然通风口的方式解决车库自然通风和采光问题,借助Airpak数值模拟技术对比分析设置机械通风系统和自然通风口两种工况下过渡季节车库的气流分布、温度分布和CO浓度场,说明车库采用自然通风口解决车库通风问题在实际工程中的可行性。     

CFD在夏季室内自然通风中的应用

针对一般家庭中的典型客厅类型,运用计算流体力学方法对其夏季自然通风特性进行了数值模拟,分析了不同风道口高度对房间的速度场、温度场的影响,结果可为住宅设计提供相关的参考依据。     

体育馆观众席预埋空调通风口施工质量控制——QC小组攻克施工难题

娄底体育中心——体育馆观众席的预埋通风口数量多且外露，其质量瑕疵影响馆内建筑观感。项目部为此组建了QC小组，就如何提高通风口施工质量展开攻关。QC小组通过现状调查和统计分析，寻找形成质量瑕疵的原因，明确目标，确认要因，有针对性地制定对策并实施质量控制措施，从而实现了通风口预留横成排、竖成列、安装周正的质量目标，有效提升了馆内建筑观感质量。