某高层建筑空调室外机运行环境的数值模拟

采用CFD模拟软件对某高层建筑空调室外机组附近环境的速度场和温度场进行数值模拟,并考虑当地气象条件的影响,通过对比有无室外风情况的模拟,观察室外机冷凝热的散发情况,得出各层空调外机互相之间的影响,结果表明本次设计中,空调室外机组的运行环境良好,外机的布置结构合理。     

某高层建筑空调室外机组的散热模拟与优化

利用CFD数值模拟方法对建筑空调室外机的散热进行模拟,研究了高层建筑中多联机空调室外机的散热对上层设备的影响。对室外不同风速以及室外机不同排列方式进行模拟,分析了室外风速对室外机散热的影响,通过对室外机排列方式的优化,满足了室外机的工作条件。     

沈阳某建筑室外风环境模拟分析

室外风环境对建筑室内风环境影响很大,尤其对建筑防风、自然通风有着决定性作用。冬季建筑防风,可有效减少气流渗透,降低采暖能耗;夏季与过渡季节的自然通风则能降低建筑空调能耗。通风提高人体热舒适感觉,通过建筑周围气流可将房间内热量扩散到外围空气中,通风还可为室内提供新鲜空气,降低室内CO2浓度。模拟分析了建筑室外风环境,以室外风场、室外风环境对室内环境影响为主要考虑内容。针对沈阳某建筑的2种设计方案,运用CFD软件对该项目在冬、夏季主导风向的典型工况下的室外风环境进行了模拟,通过分析对流场、风压,评价2种设计方案下建筑周围室外风环境质量,从而优化设计方案。     

冷凝释放热对周围环境及自然通风的影响研究

本文以分体式空调的室外机为对象,采用CFD方法,使用FLUENT软件模拟了不同的环境风速条件下,不同热释放率的室外机周围的速度场、温度场,分析室外机释放的冷凝热对建筑周围热环境的影响。还模拟了室外机置于建筑迎风面、背风面和无室外机散热影响情况下某大开口单体建筑的自然通风情况,分析通风过程中的速度、温度以及压力分布情况,研究冷凝热释放对自然通风的影响。室外机组的尺寸为900mm×900mm×300mm,距建筑外墙的距离为0.2m,距地面0.5m。由模拟结果可以看出由于热浮力的作用,热气流有明显的上升趋势,并逐渐向外墙面贴附,且影响范围很大。热空气的上升运动不仅与室外机的热释放率有关,而且与室外环境的风速也有关系。本文首次采用热污染边界层的概念来定义室外机冷凝热释放的影响范围,并对室外机的安装布置提出合理化建议。     

通风百叶参数对VRF空调系统性能的影响

为了保证建筑物外立面的美观性,VRF空调室外机的放置平台常被各种百叶窗遮挡起来,百叶窗叶片的倾斜角度、方向和开口率直接影响室外机的散热效果,从而影响空调的运行效果。本文通过数值模拟对室外机周围的气流环境进行了计算分析,研究了百叶窗参数对室外机散热器进风温度的影响。计算结果表明:叶片倾斜角度越大,室外机散热效果越差;开口率越小,室外机散热效果越差。为了满足室外机的正常运行,空调机位外立面处的百叶窗倾斜角度和开口率必须满足设计要求。     

凹槽内多台室外机安装方式的模拟研究

本文应用FLUENT软件对凹槽内同时安装多台室外机时应采用的安装距离及角度进行了研究；并以室外热环境、气流场和凹槽占有面积为评判标准对室外机的不同安装形式进行了比较，结果表明垂直安装方式不仅凹槽占有面积小，而且能够得到良好的室外热环境。     

某高层建筑空调室外机风环境模拟及优化

运用CFD数值模拟软件对某高层建筑空调室外机的风环境进行模拟,研究室外机放置于风井中时室外机散热对上层设备的影响.模拟室外机未加导风罩情况下的温度场,发现下层室外机的排风导致上层室外机回风温度升高显著.室外机增加导风罩后,室外机的回风温度平均降低了10℃左右,优化了室外机的风环境,提高了空调的制冷性能.     

某超高层建筑多联机空调室外机方案CFD模拟及优化

对某实际超高层建筑工程多联机空调室外机方案进行了CFD模拟和优化。超高层建筑室外机方案成功的一个关键因素是采取措施减弱、避免热浮力效应对室外机运行环境的不利影响。模拟结果显示,设置侧面进风通道、室外机错位摆放、去层摆放的措施对热浮力效应起到了减弱和近似切断的作用,对室外机运行环境的改善较为明显。在避难层布置室外机是避免热浮力累积效应比较行之有效的措施。考核了室外风速对室外机运行的影响。     

大型高层住宅小区室外风环境模拟分析

使用计算机模拟技术对大型住宅小区室外风环境的特点进行了模拟分析;着重对影响人居环境的住区室外风速分布以及建筑外立面的风压分布等特性进行了模拟计算;研究了此类建筑室外风环境优化设计的关键因素;研究结果表明,首层架空以及周围开敞式设计可以有效引导外部气流深入小区内部,从而改善小区的室外通风和热环境。     

温州某工业建筑室外风环境的CFD模拟分析

建筑室内风环境受室外风环境影响很大,尤其是自然通风、建筑防风效果受室外风环境决定性影响。通过采用Fluent对温州某工业建筑的室外风环境进行了模拟计算,对比分析了2个规划方案在冬夏2种工况下的速度场与压力场。在模拟结果分析基础上,提出了建议规划方案。     

3D experimental and numerical analysis of wind flow around domed-roof buildings with open and closed apertures

This paper presents experimental and numerical study of airflow distribution around a reduced-scale model of a common type of domed-roof building. Measurements are performed in an open loop wind tunnel. A new modified Counihan scheme is developed for constructing a part-depth atmospheric boundary layer (ABL). Measured quantities include: wind velocity profile, turbulence intensity and airflow pattern around the building. To conduct the experiments, a 1:54 scale model of a real domed-roof building with six windows and an aperture on the roof is fabricated and placed in the test section of the wind tunnel. In addition, using a numerical modeling, turbulent airflow around such scale model in the wind tunnel is simulated and airflow field inside and outside the model as well as ventilating discharge coefficient are computed. It is illustrated that, airflow around this type of building contains complex adjacent recirculation flows. The building with open apertures has acceptable discharge coefficient for ventilation, which can be a factor to ensure comfort condition for residents as well as complying with energy-saving considerations.     

Impact of dynamic airflow on human thermal response

Airflow fluctuation is an important factor affecting indoor thermal environments and human thermal response. In this study, dynamic airflows with different fluctuation characteristics were generated by a dynamic air supply terminal. The influence of three different kinds of airflows, constant airflow, simulated natural airflow and sinusoidal airflow, on thermal comfort was studied. Subjective experiments indicated that a dynamic airflow can cause a stronger cold sensation, and that air movement with 1/f fluctuations similar to natural wind is more acceptable than other dynamic airflows in warm environments. Moreover, the impact of draughts in dynamic airflows on human thermal response is different in neutral-warm (30 degrees C) and cool-neutral (26 degrees C) thermal environments. PRACTICAL IMPLICATIONS: By means of a dynamic air supply terminal it is possible to generate artificial airflows that simulate natural wind indoors. This kind of airflow with higher velocity is more comfortable and causes less draught sensation than the constant airflows supplied by conventional fans. While the cooling effect of this airflow is utilized in the built environment, the design temperature of air-conditioning system can be increased and the amount of energy consumption can be reduced dramatically.     

Experimental study of temperature and airflow distribution inside an urban street canyon during hot summer weather conditions. Part II: Airflow analysis

This paper presents the results of an urban measurement campaign performed in a street canyon in Athens, Greece. A number of field experimental procedures were organized during hot weather conditions, on a 24-h basis for five consecutive days during July 2002. Wind velocity measurements were conducted inside and outside the street canyon together with air and surface temperature measurements. Based on the results of air and surface temperature measurements, a further analysis is performed for the investigation of airflow inside the canyon when the ambient flow is parallel, perpendicular and oblique relative to the long canyon axis. The observed airflow characteristics are associated with the impact of thermal effects mainly induced from ground heating due to the incident solar radiation. However, the role of the finite length canyon effects related to wind circulation near street intersections, on the observed airflow patterns, is also identified.     

L形和一字形双层幕墙平均风压分布特性的试验研究

双层通风幕墙的抗风设计需考虑外层幕墙的内、外表面风压以及内层幕墙的外表面风压,其风荷载取值不同于普通单层幕墙,使得其风载取值变得复杂。通过多个不同截面形式的模型进行双层幕墙压力分布风洞试验研究。介绍风洞试验模型的设计及数据处理方法,着重分析一字形双层幕墙和L形双层幕墙的内外层幕墙的平均风压分布。试验结果表明:L形双层幕墙和一字形双层幕墙的平均风压分布有很大的不同。对于一字形双层幕墙,无论是正风压还是负风压,都主要作用在内幕墙上,外幕墙除拐角区域外所承担的风压很小。对于L形双层幕墙,其外幕墙的正风压要比内幕墙的风压大;负风压时,L形双层幕墙的短边区域是外幕墙所承担的风压大于内幕墙,其长边区域则是内幕墙所受的风压要大于外幕墙。     

Single-sided natural ventilation driven by wind pressure and temperature difference

Even though opening a window for ventilation of a room seems very simple, the flow that occurs in this situation is rather complicated. The amount of air going through the window opening will depend on the wind speed near the building, the temperatures inside and outside the room, the wind direction, the turbulence characteristics in the wind and the pressure variations caused by e.g. wind gusts. Finally, it also depends on the size, type and location of the opening. Many of these parameters are unsteady which makes the calculation of air-change rates even more complicated. In this work, full-scale wind tunnel experiments have been made with the aim of making a new expression for calculation of the airflow rate in single-sided natural ventilation. During the wind tunnel experiments it was found that the dominating driving force differs between wind speed and temperature difference depending on the ratio between the forces and the wind direction. This change is also found in the velocity profiles measured in the opening, which might change from wind dominated to temperature dominated under the same wind direction but with increasing temperature difference.     

房间自然通风运用多区域网络模型的修正

多区域网络模型计算中采用简化假设,忽略隔门位置对通风量的影响,实际运用中对通风量计算误差较大。通过风洞实验,对不同开口率工况下进行隔门位于中间和侧边时通过模型的流量进行对比;对模拟与实验进行验证后,进行数值模拟拓展,分别分析没有隔门、前隔门、后隔门、前后隔门均在时,隔门偏移量对通过模型流量的影响。结果表明,当来流风速一定时,只要当开口率足够小时能忽略来流空气动量的影响;否则,需要类比为射流模型,通过计算最大射流长度确定影响情况并进行修正。     

Wind tunnel investigation on influence of fluctuating wind direction on cross natural ventilation

The performance of wind driven natural ventilation is influenced significantly by the boundary conditions set for the wind. In real conditions the wind direction is fluctuating constantly so it is important to consider this fluctuation in experiments and simulations. This paper investigates the influence of fluctuating wind direction on cross-ventilation using wind tunnel experiments with the aim of improving the evaluation accuracy for natural ventilation. A periodically fluctuating wind direction was designed and reproduced in the experiment. Rapid Response FIDs (Flame Ionization Detector) were used to monitor the concentration of tracer gas. An index named diluting flow rate (DFR) is introduced to evaluate the ventilation performance of this kind of experiment. The results indicate that the DFRs of fluctuating cases are approximately 65–100% of the maximum airflow rate and DFR is influenced by the wind speed, the opening size and the wind direction fluctuation. Informed by the experimental data the mechanism of this combined influence is discussed in this paper.     

山地风场特性及其对输电线路风偏响应的影响

山地风场的复杂性和显著的三维特性是困扰山区输电线路抗风设计的关键问题。该研究采用CFD数值模拟与风洞试验相结合的方法研究典型单山脉地形和双山脉峡谷型地形的三维平均风场和脉动风场特征。由于风洞试验测点数及试验风速的限制，输电线路沿线各点的三维平均风场基于CFD数值模拟得到。由风洞试验获取山脉地形的湍流度、湍流积分尺度、沿线路方向的衰减系数等脉动风场参数，在此基础上采用POD法重构生成输电线路沿线各点的三维脉动风速时程，并分析比较跨越峡谷、山脊的输电线路沿线风场特征。建立连续三跨输电线路有限元模型，采用时域法研究山地风场特性对输电线路风偏响应的影响。研究结果表明：山顶、峡谷处风速显著增大，且气流爬坡将导致局部位置产生上升气流；由于近地风场加速效应的影响，沿山脊布置的输电线路全档风偏响应增幅较大，跨峡谷输电线路其爬坡段风偏响应增幅较大；上升气流主要使导线竖向风偏位移增大；山地地貌下考虑脉动风速的影响，绝缘子串风偏角风振系数宜取1.2~1.3。该研究为完善山区输电线路的抗风偏设计提供借鉴。     

半敞开式白酒库泄漏事故火灾风险分析

运用PyroSim 软件建立某大型半敞开式白酒库的单个防火分区的1∶1 模型,考虑风速的影响,计算火灾发生后的温度场和热辐射场分布,并分析温度和热辐射对罐体及构筑物的影响。结果表明：无风条件下,泄漏点附近和顶棚均处于严重热暴露环境,罐体和顶棚可能发生结构破坏。有风条件下,火焰烟气会得到一定冷却并能较快排放,事故储罐和顶棚的温度均有下降,但气流导致火源燃烧核心发生转移,泄漏点周边储罐遭受的火灾影响增大。热辐射场影响分析显示,现行标准中储罐间最小防火间距略显不足,建议在实际设计中将此距离增加到0.6D 以上。