建筑开口率对自然通风流量系数的影响分析

开口的流量系数是自然通风计算中的重要参数,而大开口自然通风的开口率对流量系数又有一定的影响。对自然通风条件下室内外的速度场和压力场进行了数值模拟,通过模拟结果分析了开口率(ε)在不同来流角度时对全压差和流量系数的影响,并给出了流量系数的取值。     

不同开口尺寸对受限空间火溢流影响研究

利用FDS模拟研究受限空间不同开口尺寸下的火溢流行为,并同现有的小尺寸实验结论进行对比分析。结果表明:当火灾总的热释放速率大于燃烧室内部的热释放速率时,室外可以得到稳定的火溢流现象;开口外墙有一定厚度时,通风因子较大,实际流入室内的空气质量流量基本满足理论值,通风因子较小,实际流入室内的空气质量流量损失较大,开口处燃烧行为的影响不可忽略;流入室内空气的燃烧参与率随着通风因子的增大而增大,超过一定值后基本稳定不变。模拟得到无量纲溢流火焰高度与热释放速率的关系与Lee小尺寸实验的数学模型大致吻合。     

低风速下单侧开口居住建筑自然通风量的快速预测方法研究

目前所用的建筑能耗模拟软件针对开窗通风量取定值,忽略了动态因素的影响,但是开窗通风量受风速大小、风向、室内外温差及开口面积等因素的影响,波动范围较大。为此,本文通过实验研究和理论计算,重点研究了北京市单开口居住建筑开窗通风量的动态变化。结果表明:通过实验研究对单开口建筑自然通风量计算式进行修正,平均误差为19.5%;北京市普通居住建筑冬季开窗通风的换气次数为2～33 h~(-1)。本文研究结果为能耗软件中单开口建筑自然通风的动态模拟提供了基础数据。     

百叶风口送风射流的数值模拟

为简化风口入流边界条件的描述,提出用N个简单开口代替不同方向出流的百叶风口,建立了N点风口模型,据此模型对不同出流条件的百叶风口射流进行了数值模拟,并就轴心速度衰减,射流扩展角及断面流速分布等与实验数据进行了对比。结果表明,当N=1或3时,模拟结果令人满意。     

自然通风计算基础—表面风压系数和开口流量系数

表面风压系数和开口流量系数是多区域模型的自然通风计算基础。本文通过文献综述系统梳理两系数的研究结果。综述表明,流态变化与两系数密切相关,伯努利原理是理解两系数变化的重要依据。建筑体型与设计、风向、上游地貌和周边建筑遮挡是影响表面风压系数的关键因素。小开口具有恒定的静止空气流量系数。大开口热压通风下的流量系数与室内外温差、开口的垂直位置、宽度和厚度有关,风压通风下的流量系数与开口率、风向和进出风口面积比有关。房间内部流动阻力对流量系数有一定影响。     

计算域对管内受限射流流动特性的影响

本文以工业通风为背景,旨在研究管内受限射流流场特性。在平行流射流送风下选取三种计算域(未扩展、圆筒式、锥筒式)进行数值模拟,探究了低速、压力出口为大气压时射流的衰减变化规律;利用CFD Fluent远场边界条件选取出口压力计算域,建立了二维轴对称模型并采用RNG k-ε二方程求解;分析了送风射流下三种计算域基本段势流特征,管流段沿流动方向截面速度分布。     

入口紊乱参数对室内空气分布的影响研究

文中采用计算机流体动力学（ＣＦＤ）的方法就风口入流参数对通风空调房间内空气流动和分布情况的影响作了数值研究,通过对条缝二维平面射流特性及其作为送风口的空调房间室内空气分布的数值计算结果与有关实验数据对比指出：在相当大的紊流入流参数范围内,最终的室内空气流动及平面射流特性的计算结果变化不大,藉此可以指导对室内空气流动进行数值模拟时的边界条件描述。     

重庆地区夜间通风条件下西外墙动态蓄热分析

针对重庆地区高温湿热的气候特征,提出采用贴附射流冷却墙体内壁面的方式进行夜间通风,并进行了实验测试和模拟分析。对比室外气象条件相近的无通风工况和采用贴附射流夜间通风工况的实测结果,分析了夜间通风对墙体壁面温度的影响。通过测试室外气象条件近似、通风速率相同、通风开启时刻不同的2个工况的数据,采用Fluent软件建立非稳态三维模型,计算了西外墙的热流密度和蓄热量。计算结果表明,该夜间通风方式可以有效降低墙体蓄热量。     

居住建筑门窗开启对自然通风特性影响的数值研究

利用Airpak软件,在非供暖空调环境下,研究了最常见的平开门和推拉窗不同开启组合方式下的流量系数,定量分析了风压通风中多开口模型的流量系数。搭建了模拟实验平台,利用多区域网络模型对实际房间通风量进行了模拟计算,发现通过改变门窗的开度能够改变有效通风面积,影响房间的自然通风量。利用DeST-h软件模拟分析了门窗不同开启模式对空调能耗的影响。     

夏冬两季室内通风降氡能耗分析

通过对室内氡的来源及氡浓度平衡的分析,建立了室内氡浓度的估算模型。在此基础上,建立了通风降氡能耗与室内氡浓度之间的计算模型,对空调房间内冬夏两季通风降氡能耗和通风换气率进行模拟。通过通风换气率整合两个模型,模拟得出室内通风降氡能耗与室内氡浓度二者之间的关系。以湖南省衡阳市住房进行模拟分析,分析结果表明,室内通风降氡能耗随着室内氡浓度降呈指数类增长,当室内氡浓度值较低时,空调通风降氡能耗要高于高浓度时降低相同氡浓度时所需能耗。     

A simulation study of ventilation and indoor gaseous pollutant transport under different window/door opening behaviors

The window/door opening behavior of occupants is a very important factor in determining the airflows and ventilation conditions in buildings, on which indoor pollutant concentration and transport are highly dependent. A two-room residence model was simulated in this study to analyze the airflow characteristics and pollutant transport under different window/door opening behaviors. Airflows were unidirectional and the residence could not be treated as a well-mixed zone when there were no temperature differences. If there were temperature differences, two-way airflow occurred at the exterior window of the room when it was open and the interior door was closed, resulting in a much larger ventilation rate than the situation without temperature differences. Strong two-way airflow occurred at the interior door in the case of the exterior window closed and interior door open, as the air in the two connected rooms was well mixed after the interior door was opened for tens of minutes. The ventilation rate of the room with double-sided ventilation was much higher than that of the room with single-sided ventilation, even though the total opening areas were the same. Opening the exterior window and closing the interior door could effectively remove pollutants from a polluted room and prevent their transport to a clean room. Field experiments were performed and the main conclusions of the simulation were verified.     

水平荷载作用下洞口对填充墙RC框架结构受力性能影响的非线性分析

在3个单层单跨、开洞率不同的填充墙钢筋混凝土框架水平荷载试验模型分析的基础上,用同样的模拟方法,对设计的19个单层单跨、不同洞口情况的填充墙钢筋混凝土框架模型进行了水平荷载作用下全过程模拟分析。分析结果表明通窗、窗洞左置和门洞右置为不利洞口情况,通窗可导致"短柱效应",使框架柱剪力明显增大,洞口率越高(或窗洞左移、门洞右移)则水平承载力和侧移刚度越低,通窗填充墙框架结构按现行方法设计存在安全隐患而非通窗类洞口填充墙框架结构是安全的。     

住宅火灾房门开启对火灾蔓延的影响

通过对典型住宅建筑火灾进行数值模拟和全尺寸实验,研究客厅起火时火灾发展趋势和不同门窗开启状况下卧室内的温度、能见度、CO体积分数,分析其对人员逃生的影响。结果表明,烟气的蔓延和聚集是危害人员安全的重要因素,客厅起火时,扑救火灾的最佳时间为起火后680 s内。关闭卧室门、开启卧室窗最多可以增加497 s的应急响应时间。     

狭长空间强扰动条件下热环境控制的数值模拟

本文针对一单侧开口,内部存在两股对称高温高速热射流且伴随多股扰动气流的狭长空间,采用全面纵向通风技术进行热环境控制、排除热污染。经数值模拟方法,得到了经济有效的全面通风临界断面风速为2．6m／s。另外,为改善局部有人区域及敏感壁面的温度,在热射流出口前端4m处设置射流风机,进行助推诱导,使排风温度提高约10～20K,提升了纵向通风的排热效果;并改善了相关人员呼吸区的温度场,使其平均温度下降约10K。     

不同车门开闭状态下地铁车厢火灾特性研究

考虑地铁车窗受高温破碎的因素,利用FDS 研究不同车门开闭状态下车厢火灾发展,对比热释放速率、温度、车窗破碎时间等。结果显示：车门开启数量对车厢火灾热释放速率的影响较大,最大热释放速率可达14.4 MW。在400 ℃和600 ℃的破碎温度下,当车门开启数量大于3 扇和4 扇时,车厢火灾最大热释放速率下降。火灾发展初期,车门开启数量对车厢内温度分布影响不大,全面发展阶段时,车门开启会造成温度跳跃式增长。对于车厢火灾,不同车门开启状态会影响车窗破碎的顺序、位置及时间。当1 号车门开启时,400 ℃工况下,火源两侧窗户破碎时间相比600 ℃工况最多提前1 066 s。     

Large-eddy simulation of the containment failure in isolation rooms with a sliding door—An experimental and modelling study

In hospital isolation rooms, door operation can lead to containment failures and airborne pathogen dispersal into the surrounding spaces. Sliding doors can reduce the containment failure arising from the door motion induced airflows, as compared to the hinged doors that are typically used in healthcare facilities. Such airflow leakage can be measured quantitatively using tracer gas techniques, but detailed observation of the turbulent flow features is very difficult. However, a comprehensive understanding of these flows is important when designing doors to further reduce such containment failures. Experiments and Computational Fluid Dynamics (CFD) modelling, by using Large-Eddy Simulation (LES) flow solver, were used to study airflow patterns in a full-scale mock-up, consisting of a sliding door separating two identical rooms (i.e. one isolation room attached to an antechamber). A single sliding door open/ hold-open/ closing cycle was studied. Additional variables included human passage through the doorway and imposing a temperature difference between the two rooms. The general structures of computationally-simulated flow features were validated by comparing the results to smoke visualizations of identical full-scale experimental set-ups. It was found that without passage the air volume leakage across the doorway was first dominated by vortex shedding in the wake of the door, but during a prolonged hold-open period a possible temperature difference soon became the predominant driving force. Passage generates a short and powerful pulse of leakage flow rate even if the walker stops to wait for the door to open.     

Simulation of inhalable aerosol particle distribution generated from cooking by Eulerian approach with RNG k–epsilon turbulence model and pollution exposure in a residential kitchen space

Cooking-generated fume contains large amounts of fine particle pollutants with high concentration. To study the influence of the aerosol particle pollutant in kitchen, a typical format of residential kitchen in northern China is selected in this paper. FLUENT software is applied to simulate interior space airflow as well as pollutant mass fraction in breathing-section and cooking-section area in the residential kitchen under different vent cases. Furthermore, occupant’s exposure to inhalable aerosol particle is obtained integrated with human inhale model and pollution exposure calculation model. The results demonstrate that cooking side of respiratory region in pollutant mass fraction can be significantly reduced when opening the door, but mass fraction gradient is larger in the vicinity of the stove. The average pollution exposure in the maximum value is about 90 times than that of the minimum value around the cooking personnel with the most adverse conditions in winter when the doors and windows are all closed. The research output can provide valuable reference for the further study on fine particles concentration level as well as to determine individual intake fraction of particles generated in the process of cooking in the residential kitchen.     

The influence of gaps of fire-resisting doors on the smoke spread in a building fire

Many building codes stipulate the need for fire-rated doors to be closely fitted around their edges to impede the passage of smoke and flame. To ensure the smooth opening of the doors, gaps between the door panels and the walls and floor cannot be totally eliminated. Depending on the country where the building code is enforced, the maximum permissible door gap requirement varies substantially. To better understand the influence of gap sizes on the smoke spread, a numerical study is performed on the different door gap configurations affecting the smoke egress in an enclosure fire. The results show that the height of the door gaps has a significant effect on the pressure and temperature distribution in controlling the smoke spreading. Larger door gaps have shown to allow more hot smoke transgressing through the door gaps as well as cold air re-entraining back into the burn room. Fire-rated door with a 3 mm door gap have demonstrated to be the best measure for impeding smoke spread while maintaining reasonable smoothness for the door movement.     

可调通风型站台门系统在地铁火灾中的适用性

以青岛某地铁车站为研究对象,通过 PyroSim 软件对火灾场景进行数值模拟,设置屏蔽门与通风窗不同的开闭组合方式,着重分析站台内整体和局部测点的温度、CO 质量浓度、能见度等指标。结果表明,相比于单独开启通风窗的工况,同时开启屏蔽门和通风窗的排烟效果较优,单独开启屏蔽门时的排烟效果最差。     

Wind-induced ventilation performances and airflow characteristics in an areaway-attached basement with a single-sided opening

In the present study, we performed both wind tunnel experiments and numerical simulations on a scale model with the focus on wind-driven natural ventilation in an areaway-attached basement with a single-sided opening. In the experiments, the mean value of the effective ventilation rate, purging flow rate (PFR) was measured for nine wind incidence angels based on the homogeneous emission rate method. The experimental results were used to validate two numerical approaches: Reynolds averaged Navier–Stokes (RANS) modeling and large-eddy simulation (LES). The influences of inflow turbulent fluctuations for LES modeling were also examined. The comparisons between the experiment and the numerical simulation indicate that LES can provide more accurate results than RANS and the inflow turbulent fluctuations should be taken into account for LES modeling. Based on LES with the inflow turbulent fluctuations, the mean airflow patterns within and around the areaway-attached basement were further studied for different wind incidence angles to investigate the influence of wind direction on ventilation performance in the areaway space. Furthermore, the relationships between the effective ventilation rate and the kinetic energy in the basement space were analyzed for three wind directions: 0°, 90° and 180°. A close correlation was found between the mean values, whereas the corresponding time variations showed large discrepancies. Finally, we compared the effective ventilation rate obtained using the homogeneous emission rate method and the airflow rates through the opening using two integration procedures. The effective ventilation rates were found lower than the airflow rates through the opening.