高海拔地区雷电强度的初步探讨

<正> 目前,国内在讨论高海拔地区外绝缘电气强度时,一般仅考虑气压、气温和湿度三个参数。我认为,除这三个参数外,还应探讨雷电强度的影响。这对于110千伏及以下电气设备的外绝缘,尤为重要。国外有关文献早已认为,高海拔地区雷电强度比平原地区为小。如1939年苏联В·В·Бургсдорф指出:海拔高程在2500     

青藏高原低气压环境下钢管混凝土的核心混凝土密实性评估方法研究

为研究高海拔低气压条件对混凝土抗压强度与超声波速相关性的影响,分别在高海拔地区(西藏山南)与低海拔地区(广西南宁)进行了不同水灰比混凝土试件的制备与强度、超声波速测试,研究表明,低气压条件下7～56d龄期混凝土的抗压强度比标准气压条件下相同配合比混凝土高出约5.8%～38.2%;低气压条件下混凝土的超声波速低于标准气压条件下相同强度混凝土,不同气压下混凝土超声波速与强度存在不同的线性关系,并在此基础上提出了不同气压下混凝土超声波速与强度的相关关系模型。通过压汞试验(MIP)及数值模拟分析,揭示了混凝土超声波速受微观结构中固体超声波速及孔隙率两因素共同影响的机理,建立了不同气压下混凝土固体超声波速的计算模型。基于混凝土超声波速与强度的相关性及不同灌注工艺的密实程度,提出了不同气压条件下钢管混凝土的核心混凝土密实性评估方法。     

列车前窗玻璃抗飞弹性能仿真分析

本文对一种新头型列车前窗玻璃进行了抗飞弹性能仿真分析,提供了一种前窗玻璃抗飞弹性能的仿真分析方法,给出了该玻璃受到冲击后的损伤结果,供前窗玻璃设计、生产使用。     

轨道客车侧顶窗玻璃抗冰雹冲击仿真分析

设计了一种抗冰雹冲击的轨道客车侧顶窗玻璃,并基于显示积分非线性动力学理论利用LS-DYNA软件研究了玻璃抗冰雹撞击的极限速度。同时,综合列车最高运行速度、冰雹自由落体速度、冰雹和玻璃自身机械性能等推导出冰雹实际坠落的最大速度,评估玻璃的抗冰雹冲击性能。结果表明,直径40mm、速度84m/s的冰雹才能损坏玻璃,超过冰雹实际能达到的速度2.7倍,因此,所设计的侧顶窗玻璃能抵抗通常的冰雹冲击。     

高原地区砖瓦厂隧道窑的优化设计

隧道窑是砖瓦企业中的核心设备,它直接影响产品的产量和质量.目前,西安墙材院在西藏拉萨设计一条年产6000万块页岩砖厂,选用两条4.6 m宽隧道窑.以往隧道窑的设计是针对低海拔地区设计的,热工设计的基础是低海拨地区的气压及有关参数.拉萨地区海拔3670 m,属于高海拔地区,高原大气变化对隧道窑的焙烧有什么影响,我们应采取何种应对措施,这些都是拉萨项目中必须考虑的.     

中空玻璃窗的清洗方法

多层中空玻璃窗使用时间长了,密封性变差,在玻璃片之间出现冷凝水,形成一层奶白色层,影响玻璃的美观与性能。为此用户往往要更换玻璃甚至整套窗户。荷兰的一些专家发明了一种清洗多层中空玻璃的方法,延长了玻璃窗的使用寿命,清洗费用只及更换新窗玻璃的四分之一。这种方法采用一水力推动的专用钻孔机。钻头在玻璃的对角线两端各钻一个小孔,钻孔机可将钻下的部分     

高海拔地区气候特性及沥青路面铺筑关键技术工艺

为探究高海拔地区沥青路面铺筑关键技术工艺,本文通过中国气象数据网查取了不同海拔等级下典型地区的气候特征,并分析了各海拔分区的累年月平均气温、累年月平均最高气温、累年月平均最低气温和累年月平均气温日较差;之后,从热传导、热对流、热辐射三个方面分析了沥青混合料的降温机理;最后,根据高海拔地区气候特征,提出了高海拔地区沥青路面铺筑关键工艺。结果表明,各海拔高度地区温度差异明显,尤其是累年月平均气温日较差,相邻海拔分区城市,日较差可达10℃以上;在每年各月之间,各海拔分区地区,在夏季(7—8月)温差较显著。沥青混合料在运输和施工过程中的温度散失主要来源于热传导、热对流、热辐射三个方面。为保障高海拔地区沥青路面施工质量,应在原材料选取、拌和温度、运输保温措施上进行严格控制。     

用磁吹避雷器保护高海拔地区电器的探讨

<正> 我国幅员辽阔,西北、西南有很多地区海拔超过1000米。这些高海拔地区大气条件比较恶劣,其中一个突出问题,是由于气压和绝对湿度的降低,使空气间隙、绝缘子和电气设备外绝缘的放电电压降低,严重威胁着电网的安全运行。长期以来,这个问题一直困扰着电站配电装置的设计和电器的制造     

美国加迪安公司介绍一种低辐射玻璃

美国加迪安公司介绍一种低辐射建筑玻璃制品。这种新的玻璃制品可借助于太阳光来降低能源成本。据说用这种玻璃制作的双层窗玻璃,其节能效果与三层窗玻璃(普通玻璃制作的)的节能效果相似。在气候较冷的地区,低辐射玻璃内侧涂有     

中空窗玻璃贴低辐射膜的性能研究

热阻和太阳能透过率是分别反映窗玻璃热工性能和光学性能的参数.在不贴膜和室内贴低辐射膜2种情况下,对中空窗玻璃的热阻和太阳能透过率进行实验研究,分析和比较2种情况下的窗玻璃性能及其对节能性的影响.结果表明,实验所用中空窗的固定窗和推拉窗2部分,贴膜后传热阻分别增大31.1%和40.7%,传热系数分别降低23.7%和28.8%.对于玻璃的太阳能透过率,贴膜后从40%减少到28.6%,透过玻璃的辐射热减少28.5%.     

温度对高速动车组侧窗抗风压载荷性能的影响

通过测量分析-50℃~40℃范围内不同温度下高速动车组侧窗玻璃和铝合金窗框的应力变化及整体车窗的密封性,研究温度对高速动车组侧窗抗风压载荷性能的影响。结果表明,温度对高速动车组侧窗的应力分布具有一定影响,在低温下侧窗玻璃的角点位置应力最大,在高温下侧窗玻璃的长边中部位置应力最大。在-50℃~40℃范围内,现有设计的侧窗可以承受±6000Pa风压载荷作用,保持车窗结构完好,密封性能良好。     

Analysis and modelling of window and glazing systems energy performance for a well insulated residential building

The energy performance of a window depends on its thermal transmittance, the glazing solar transmittance, and the air leakage due to the frame and installation airtightness.In new installations air leakage represents a quite small term which is almost independent from the window and in particular from the glazing system selection.The contributions of the two other terms to the building thermal balance are not independent to each other: the most effective thermal insulating glazing, as triple glazings, are generally characterized by low solar transmittance reducing solar gains. The thermal energy balance of the building is then affected not only in summer but also in winter, potentially increasing heating energy need.This work evaluates the impact of different kinds of glazing systems (two double and two triple glazings), window size (from 16% to 41% of window to floor area ratio), orientation of the main windowed façade and internal gains on winter and summer energy need and peak loads of a well insulated residential building. The climatic data of four localities of central and southern Europe have been considered: Paris, Milan, Nice and Rome. A statistical analysis has been performed on the results in order to identify the most influencing parameters.     

Finite element modelling of architectural laminated glass

Laminated glass (LG) comprises two or more glass plates bonded together with elastomeric interlayer. Automobile and aircraft industries have used LG for years because of its ability to maintain closure of window openings following fracture. In the last decade, the architectural industry began to utilise the potential of LG as the best glazing material for building fenestrations that might experience extreme loadings. Polyvinyl butyral (PVB) interlayer and recently advanced polymer interlayer have relatively small thickness in comparison with that of the glass plates in LG. In addition, the structural properties of the interlayer materials vary radically from those of window glass. These issues make analysis of LG difficult. This article presents a higher order finite element model (FEM) to analyse LG under uniform loading. The formulated model can analyse LG with different glass plate types and different interlayer thicknesses over a wide temperature range. While not as comprehensive as some analytical techniques for LG, this model has the advantage of being able to handle different shapes (rectangular, trapezoidal, triangular, etc.) and boundary conditions.     

The function of solar absorbing window as water-heating device

While window glazing will be more and more extensively used in modern architecture, the increase in space thermal load as a result will deteriorate the global environment, incurring problems of air pollution and climate change. By connecting the cavity of a double pane window to a water-flow circuit, absorbed solar heat at the window glasses can be readily removed by the water stream. The water passage in this way can effectively lower the glass pane temperature, reduce room heat gain and therefore, the air-conditioning electricity consumption. Thermal comfort can be enhanced. Furthermore, the water-flow window can function as a hot-water preheating device. This article reports the integrative thermal performance of a water-flow absorbing window as compared to the conventional single and double pane absorptive glazing. The results based on the operation in health club environment are very encouraging. This demonstrates its good application potential in domestic–commercial buildings with stable hot-water demands.     

低气压环境对空调器制冷能力的影响初探

分别从理论和实验两方面研究低气压环境对蒸发器空气侧换热系数的影响。低气压环境下较小的空气密度会降低蒸发器空气侧换热系数，较小的空气绝对含湿量造成潜热换热量的减小。低气压环境同时会影响制冷剂侧的沸腾换热，并造成制冷量的进一步下降。     

CFD study of the thermal environment in an air-conditioned train station building

This study used the computational fluid dynamics (CFD) method to evaluate the indoor thermal environment of an air-conditioned train station building under three types of air-conditioning design schemes. The impacts of air-conditioning design parameters such as supply air temperature, velocity, altitude and angle of incidence were also investigated. The numerical results showed that if the waiting hall and entrance hall of the train station building were connected to each other and served with the cooling air respectively, when the cooling loads in the two halls were fixed and air-conditioning systems were designed properly, altering largely the cooling air supply scheme in the waiting hall while keeping the cooling air supply scheme in the entrance hall unchanged would have significant effects on the air distribution and thermal comfort in the occupied region of the waiting hall but may have some minor effects on those in the occupied region of the entrance hall. The uniformities of velocity and temperature distributions in the occupied region of waiting hall were satisfactory when side supply scheme was applied. Changing supply air temperature, velocity, altitude and angle of incidence would yield great effects on the thermal environment in the train station building. For the stratified air-conditioning design in the train station building, in order to obtain the satisfactory thermal comfort in the occupied region, the mid-height of the building was found to be a good position for the cooling air supply and the supply angle of 0° from the horizontal could be recommendable. The results also indicated that analyzing the effects of air-conditioning design parameters on the building environment with CFD was an effective method to find the way to optimize the air-conditioning design scheme.     

Glazing daylight transmittances: a field survey of windows in urban areas

The effect of urban air pollution on glazing daylight transmittance was investigated by measuring the percentage loss in glazing transmittance of a number of windows throughout a large city in the UK. A total of 430 windows in a range of building types and locations were used to create the database for this window survey. The measurements were taken under overcast sky conditions to minimise errors that could occur during periods of rapidly changing sky luminance. In addition, two adjacent photocells were used so that simultaneous comparative measurements were taken. In general it was observed that the loss in transmittance for a vertical window did not usually exceed 10%. The factors that most significantly reduced glazing daylight transmittance were (i) the function/use of the building or the rooms within, (ii) the inclination of the window and (iii) the shading of the window by overhangs. It is, therefore, suggested that future daylight design guidelines should include these factors.     

A simplified method to estimate energy savings of artificial lighting use from daylighting

This paper provides a simplified analysis method to evaluate the potential of daylighting to save energy associated with electric lighting use. Specifically, impacts on daylighting performance are investigated for several combinations of building geometry, window opening size, and glazing type for four geographical locations in the United States. Four building geometries with various window-to-floor areas, along with different glazing types have been analyzed. It was determined that for most commercial buildings with glass transmittance values above 0.5, increasing window area to floor area ratio above 0.5, daylighting does not provide significant additional lighting energy savings. A direct correlation has been established between window transmittance and window area on annual lighting reductions. A model is proposed to estimate lighting energy savings given perimeter area, window area, and window type. Verification and validation of the model's predictions are demonstrated using results from building energy simulation as well as experimental data.     

Numerical analysis of airflow around a passenger train entering the tunnel

In this paper, the characteristics of train-tunnel interaction at a tunnel entrance has been investigated numerically. A three-dimensional numerical model using the remeshing method for the moving boundary of a passenger train in Iran railway was applied. The turbulent flows generated by the moving train in a tunnel were simulated by the RNG κ−ε turbulence model. The simulations have been carried out to understand the effect of the train speed as well as the influences of the hoods and air vents on the pressure waves, drag, and side force coefficients. The results show that the maximum drag coefficient occurs when the train enters the tunnel and is equal to 2.2. The air vents and enlarged hood at the portal are demonstrated to attenuate the pressure gradient and drag coefficient about 28% and 36%, respectively. Furthermore when train is entering the tunnel asymmetrically, a side force is created that pushes the train toward the tunnel wall, which the maximum side force is 900 N.     

Glazing energy performance and design optimization with daylighting

This study systematically explores the influence of glazing systems on component loads and annual energy use in prototypical office buildings. The DOE-2.1B building energy simulation program, which contains an integrated daylighting model, is used to determine fenestration energy performance in diverse climates. The sensitivity of total energy use to orientation, window area, glazing properties (U-value, shading coefficient, visible transmittance), window management strategy, installed lighting power, and lighting control strategy are all described. We examine the conditions under which daylighting reduces net anual energy use as well as those conditions under which energy use may increase. Combinations of wall and fenestration properties that minimize net energy requirements as a function of climate and orientation are described.