基于零方程湍流模型大空间数据机房气流组织数值模拟

建立了零方程湍流模型和机房物理模型,对大空间数据机房的室内热环境进行了模拟研究,比较分析了机房内不同高度平面的温度场和速度场。模拟结果显示,机房温度分布极不均匀,各个高度机架周围热点温度明显偏高,在机房右侧闲置区域由于两股逆向气流的混合产生旋涡现象,形成负压区并卷吸了冷通道的空气,造成极大的冷量浪费。提出冷通道封闭、右侧低压区加隔板、空调侧加隔墙3种改进措施,模拟了各种措施下机房内的热环境状况。结果表明,3种措施均可以有效地改善机房内的温度分布,消除热点温度区域,实现冷量的有效利用。     

以损失指数分析评价数据机房热环境

回顾了数据机房常用的热环境评价指标,定义了损失指数,从考察损失的角度分析了机房内的传热和流动过程。以典型机房模型为例,通过数值模拟将常用的机房热环境评价指标与损失指数进行了对比分析,验证了该指数的可行性。损失指数不仅能反映数据机房的热环境,还能分析由冷热气流掺混等导致机房冷却效率低下的因素。提出了相应的改进措施,对提高数据机房的能量利用有参考意义。     

基于■损失的数据机房热环境优化研究

针对现有数据机房热环境评价指标不足,将热学原理■损失方法应用于机房热环境评价。以某典型数据中心机房为例,建立了风管上送风、地板下送风和机柜前送风后回风3种气流组织模型,将热学原理■损失评价结果与数值模拟结果进行了对比,验证了该方法的合理性。以地板下送风为例,运用■损失方法,评估了封闭冷/热通道优化方式对数据机房热环境的影响程度。与其他指标评价方法相比,■损失评价方法不仅可以有效评价数据机房气流组织形式,还可以量化系统传热过程中冷热气流掺混造成的热损失,可以更加全面地评价机房热环境。     

机房服务器位置与热区气流关系研究

以FLUENT软件作为模拟工具,在数据机房热区里建立内气流流动与传热的数值模型。对数据机房热区内模拟的数据进行分析,得出需重点考虑SUN4900服务器排风对气流的影响。结果表明:数据机房服务器位置对热区气流影响较大,为了防止气流对撞,服务器之间需上下错开一定的高度,同时同侧SUN4900服务器需上下交错一定的距离。     

数据中心地板送风和IT设备机柜散热的CFD模拟方法总结和比较

数据机房的气流组织和温度场可以为评价数据机房热工环境和数据机房节能改造提供有力的依据。目前,运用CFD模拟数据机房气流组织是常用的分析方法,提高CFD在数据机房气流组织模拟精度至关重要。在CFD建模的环节中,对于地板送风的模拟直接关系到垂直方向送风初速度和速度梯度变化;而IT设备机柜散热的模型建立,关系到热量的分布和散热,这两个问题是影响模拟精度的关键因素;总结了目前常用的几种数据机房地板送风和IT设备散热的模拟方法,与实测数据进行对比,比较不同建模方式的优势与缺点。     

数据中心机房气流组织研究在某机房的应用

以联通某数据中心实例为对象,通过CFD模拟软件6Sigma Room建立机房模型,对其架空地板送风、上部回风的气流组织形式和室内热环境进行模拟,对机房内出现局部热点的原因进行分析。采用定点背板空调改造方案后,与改造前的气流组织及室内热环境进行了对比。结果表明:增加背板空调后,机房局部热点问题消失,冷热气流混合减小。     

基于对流辐射耦合换热的新型数据机房空调系统

针对现有数据机房存在局部环境热点的问题,提出了一种新型的对流辐射耦合换热空调系统。建立数值模型对典型数据机房空调系统进行了模拟研究,通过将模拟结果与实验数据进行对比分析,验证了该模型的可靠性。对比研究了新型数据机房空调系统与传统数据机房空调系统的流场分布及制冷性能。结果表明:在相同的送风温度下,新型数据机房空调系统的机架进口温度分布更加均匀;在满足ASHRAE标准的前提下,新型数据机房空调系统的送风温度可以提高2℃,能够有效降低数据机房的电能利用效率;辐射板对数据机房局部热点的改善效果明显,辐射板的温度设置为31℃较为合理。     

设备布局对机房热环境影响的模拟研究

由于气流组织不合理导致数据机房存在局部过热以及冷风浪费等问题。对设备布局变化的多种机房模型进行了数值模拟,获得了多种不同设备布局下机房的速度场、温度场以及典型平面的平均温度。结果表明,机房内设备的不同布局结构会影响机房内的气流组织分布,对于不同规模的数据机房都存在较优的设备布局,能够实现数据机房的节能。具体来说,空调斜对放置与机柜间距适当增大相结合最佳。     

从气流组织优化角度确定数据机房建筑条件

以标准化数据机房工程实例为对象,运用CFD模拟软件建立了数学和物理模型,根据实际运行工况对数据机房气流组织进行了模拟,得出该数据机房单机柜功率的最大值。模拟分析了架空地板高度和是否封闭冷热通道2个因素对服务器冷却效果的影响,从气流组织优化角度对标准化数据机房的建筑条件给出了合理化建议。     

绿化率与居住区竖向微气候环境相关性研究

基于人们对居住环境舒适度要求的提高及生态节能的需要,绿化率对居住小区的热舒适性尤为重要。文章以西安居住区为研究对象,应用ENVI-met数值模拟软件对小区风环境和热环境进行了模拟,得出了3种绿化率条件下不同竖直高度上的温度和风速比。研究对高层居住区的规划和建筑设计提供了数据支撑。     

Simulating the human body's microclimate using automatic coupling of CFD and an advanced thermoregulation model

This study aims to develop an approach to couple a computational fluid dynamics (CFD) solver to the University of California, Berkeley (UCB) thermal comfort model to accurately evaluate thermal comfort. The coupling was made using an iterative JavaScript to automatically transfer data for each individual segment of the human body back and forth between the CFD solver and the UCB model until reaching convergence defined by a stopping criterion. The location from which data are transferred to the UCB model was determined using a new approach based on the temperature difference between subsequent points on the temperature profile curve in the vicinity of the body surface. This approach was used because the microclimate surrounding the human body differs in thickness depending on the body segment and the surrounding environment. To accurately simulate the thermal environment, the numerical model was validated beforehand using experimental data collected in a climate chamber equipped with a thermal manikin. Furthermore, an example of the practical implementations of this coupling is reported in this paper through radiant floor cooling simulation cases, in which overall and local thermal sensation and comfort were investigated using the coupled UCB model.     

Performance assessment of a ductless personalized ventilation system using a validated CFD model

The aim of this study is twofold: to validate a computational fluid dynamics (CFD) model, and then to use the validated model to evaluate the performance of a ductless personalized ventilation (DPV) system. To validate the numerical model, a series of measurements was conducted in a climate chamber equipped with a thermal manikin. Various turbulence models, settings, and options were tested; simulation results were compared to the measured data to determine the turbulence model and solver settings that achieve the best agreement between the measured and simulated values. Subsequently, the validated CFD model was then used to evaluate the thermal environment and indoor air quality in a room equipped with a DPV system combined with displacement ventilation. Results from the numerical model were then used to quantify thermal sensation and comfort using the UC Berkeley thermal comfort model.     

Numerical simulation of radiant floor cooling system: The effects of thermal resistance of pipe and water velocity on the performance

Using the existing floor heating system, the radiant floor cooling system can be used as an alternative to the conventional all-air cooling systems. In this paper, a numerical model for the radiant floor cooling system is built using finite volume method. The objective of this study is to research the effects of the thermal resistance of pipe and water velocity on the performance of the radiant floor cooling system. In order to provide better heat transfer simulation in the pipe, composite grids are used in the model. The numerical floor surface temperature and the heat flux are in agreement with the measured results. The results illustrate that the pipe has effect on the performance of the radiant floor cooling system when the thermal conductivity of the pipe is low. However, the effect of the water velocity on the performance of the cooling system is not great. The model is helpful to calculate and design such kind of radiant floor cooling systems.     

Measured heat losses through a real ground floor slab

The measured variation of heat losses across the floor slab emphasize the potential benefits to be gained from the use of edge insulation. In general, thermal transmittance values calculated from the measured data are found to be in reasonable agreement with values determined from design guides.     

成都地区既有居住建筑顶层端头房间室内热环境研究与改善

应用DeST—h软件对成都地区某居住建筑室内基础室温进行模拟计算,研究建筑物不同楼层房间的室内热环境状况,发现顶层、端头房间的室内热环境最为恶劣。结合装修,对外围护结构提出相应的改造措施,计算结果表明改造后顶层端头房间室内热环境得到明显改善。     

A calculation method for the floor surface temperature in radiant floor system

In this paper, a calculation method for the floor surface temperature in radiant floor heating/cooling system is proposed, a new formula is derived to estimate the floor surface temperature. The floor is divided into two layers. The correlation for the thermal conductivity of the lower layer is developed based on the numerical model of the radiant floor system built in this paper. The results show that the floor surface temperature values from the proposed method are in agreement with the experimental and numerical values.     

水平送风工况下CRAC机组间距对机架散热的影响

本文研究架空地板数据中心CRAC水平送风方式下四种CRAC机组送风间距对机房内机架散热和穿孔地板气流分布的影响,分析四种CRAC送风间距的机房机架入口温度和通过穿孔地板的体积流量,比较四种工况的机架设备散热情况和热循环,为今后数据机房设计以及机房热管理和节能改造提供了依据。     

基于下送中回气流组织Block模型内壁面对流传热系数的讨论

以大空间缩尺模型实验室为研究对象,基于Block模型,采用2种常数法及3种温差法的表面对流传热系数取值方法,计算室内在下送中回气流组织下的空气垂直温度分布。通过与实验值的比较发现,对流传热系数温差法计算结果优于常数法。其中一种对流传热系数温差法得到的空气垂直温度与实测温度的误差最小。     

Floor heating and cooling combined with displacement ventilation: Possibilities and limitations

Design guidelines envisage that floor heating can be used together with displacement ventilation (DV), provided that the supply air is not overly heated before it can reach heat and contaminant sources. If this is not controlled a mixing flow pattern could occur in the room. The use of floor cooling with DV is also considered possible, although draught risk at ankle level and vertical air temperature differences must be controlled carefully, because they could increase.Few studies on these topics were found in the literature.An indoor environmental chamber was set up to obtain measurements aimed at analysing the possibilities and limitations of combining floor heating/cooling with DV. Air temperature profiles, air velocity profiles, surface temperatures and ventilation effectiveness were measured under different environmental conditions that may occur in practice. These values were compared to equivalent temperature measurements obtained using a thermal manikin.The measurements show that floor heating can be used with DV, obtaining high ventilation effectiveness values. A correlation between the floor heating capacity and the air temperature profile in the room was found. Measurements showed that floor cooling does not increase draught risk at ankle level, although it does increase vertical air temperature differences.