A STUDY ON THE CHARACTERISTICS OF INTERNAL ANDEXTERNAL WALL SURFACE TEMPERATUREIN THE URBAN AREA

Internal and external wall surface temperatures (Tws) in April, August and December in Kunming, a city in low latitude plateau, were investigated. Results showed that the Tws in April were of the highest among the three, followed by August and December. The Tws differences among walls with different orientation were higher in April and December when the weather tends to be sunny, and lower in August with more cloudy days in the time. In April and August, Tws of E-wall was the highest, followed by S- and N-wall. But in December Tws of S-wall might be sometimes higher than E one. Diurnal range of internal Tws was usually smaller than that of the external, with also a time lag for the occurrence of its maximum and minimum. The results can serve as a basis for further research on building microclimate and urban architecture designs. It also gives suggestions for similar studies in other areas.

Thermodynamic Equilibrium of the Saturated Fluid with a Free Surface Area and the Internal Energy as a Function of the Phase-Specific Volumes and Vapor Pressure

This study is concerned with describing the thermodynamic equilibrium of the saturated fluid with and without a free surface area A. Discussion of the role of A as system variable of the interface phase and an estimate of the ratio of the respective free energies of systems with and without A show that the system variables given by Gibbs suffice to describe the volumetric properties of the fluid. The well-known Gibbsian expressions for the internal energies of the two-phase fluid, namely for the vapor and for the condensate (liquid or solid), only differ with respect to the phase-specific volumes and . The saturation temperature T, vapor presssure p, and chemical potential are intensive parameters, each of which has the same value everywhere within the fluid, and hence are phase-independent quantities. If one succeeds in representing as a function of and , then the internal energies can also be described by expressions that only differ from one another with respect to their dependence on and . Here it is shown that can be uniquely expressed by the volume function . Therefore, the internal energies can be represented explicitly as functions of the vapor pressure and volumes of the saturated vapor and condensate and are absolutely determined. The hitherto existing problem of applied thermodynamics, calculating the internal energy from the measurable quantities T, p, , and , is thus solved. The same method applies to the calculation of the entropy, chemical potential, and heat capacity.

Band structure,Fermi surface,elastic,thermodynamic,and optical properties of AlZr3,AlCu3,and AlCu2Zr:First-principles study

The electronic properties（Fermi surface,band structure,and density of states（DOS）） of Al-based alloys AlM3（M=Zr and Cu） and AlCu2Zr are investigated using the first-principles pseudopotential plane wave method within the generalized gradient approximation（GGA）.The structural parameters and elastic constants are evaluated and compared with other available data.Also,the pressure dependences of mechanical properties of the compounds are studied.The temperature dependence of adiabatic bulk modulus,Debye temperature,specific heat,thermal expansion coefficient,entropy,and internal energy are all obtained for the first time through quasi-harmonic Debye model with phononic effects for T = 0 K-100 K.The parameters of optical properties（dielectric functions,refractive index,extinction coefficient,absorption spectrum,conductivity,energy-loss spectrum,and reflectivity） of the compounds are calculated and discussed for the first time.The reflectivities of the materials are quite high in the IR-visible-UV region up to ~ 15 eV,showing that they promise to be good coating materials to avoid solar heating.Some of the properties are also compared with those of the Al-based Ni3 Al compound.

Near ground air temperature calculation model based on heat transfer of vertical turbulent and horizontal air flow

In order to calculate the air temperature of the near surface layer in urban environment,the surface layer air was divided into several sections in the vertical direction,and some energy balance equations were developed for each air layer,in which the heat exchange due to vertical turbulence and horizontal air flow was taken into account.Then,the vertical temperature distribution of the surface layer air was obtained through the coupled calculation using the energy balance equations of underlying surfaces and building walls.Moreover,the measured air temperatures in a small area(with a horizontal scale of less than 500 m) and a large area(with a horizontal scale of more than 1 000 m) in Guangzhou in summer were used to validate the proposed model.The calculated results accord well with the measured ones,with a maximum relative error of 4.18%.It is thus concluded that the proposed model is a high-accuracy method to theoretically analyze the urban heat island and the thermal environment.

Modeling of Air Temperature for Heat Exchange due to Vertical Turbulence and Horizontal Air Flow

In order to calculate the air temperature of the near surface layer in urban environment,the surface layer air was divided into several layers in the vertical direction,and some energy balance equations were developed for each air layer,in which the heat exchange due to vertical turbulence and horizontal air flow was taken into account.Then,the vertical temperature distribution of the surface layer air was obtained through the coupled calculation using the energy balance equations of underlying surfaces and building walls.Moreover,the measured air temperatures in a small area(with a horizontal scale of less than 500 m)and a large area(with a horizontal scale of more than 1 000 m)in Guangzhou in summer were used to validate the proposed model.The calculated results agree well with the measured ones,with a maximum relative error of 4.18%.It is thus concluded that the proposed model is a high-accuracy method to theoretically analyze the urban heat island and the thermal environment.

WUDAPT方法的局地气候区分类流程优化及地表热环境特征分析——以西安主城区为例

局地气候区(Local Climate Zone,LCZ)是依据城市地表特征进行分区的城市气候定量分析方法。现有WUDAPT分类流程(World Urban Database and Access Portal ToolsM,WUDAPT)由于人为样本类别识别偏差造成建成类型分类精度明显低于自然类型,本文以西安主城区为例对这一分类流程进行优化,优化流程采用GIS计算和归一化差异指数计算达到预先识别建筑形态特征与自然覆盖属性的目的,结果用于提取不同LCZ样本类型。采用大气校正法反演得到研究区内地表温度数据,与LCZ分类地图叠置分析得到不同LCZ地表热环境差异与规律。从LCZ分类结果来看,优化的分类流程制作的LCZ地图总体分类精度、建成类型分类精度和自然覆盖类型分类精度分别为79.76%、79.97%和79.41%,相比常规流程下的精度分别提升17.4%、19.4%和9.5%,Kappa系数为0.78,一致性达到显著水平。从地表温度分析结果来看,建成类型LCZ地表温度受建筑密度、高度、功能等共同影响,建筑高度相近时密度越大地表温度越高,而建筑密度一定高度越高地表温度越低,LCZ10受人为热影响而地表温度最高。自然覆盖类型地表温度整体低于建成类型,但仍表现出显著的类间差异,如无植被覆盖的硬化地面与裸地均高于植被覆盖类型,低矮植被与稀疏林地均高于稠密林地,水体地表温度最低。从局地气候区分类视角合理规划不同LCZ用地类型可达到改善城市地表热环境的目的。

Suppression of Surface Burn in Grinding of Titanium Alloy TC4 Using a Self-inhaling Internal Cooling Wheel

Based on analysis of surface average temperature and burn degree, this article obtains the threshold temperature of surface burn in grinding titanium alloy with cup wheels. Meanwhile, the impact of the burn degree on the metallographic structure of workpiece surface and metallurgical phase transformations is investigated. In order to reduce the grinding temperature and improve the grinding efficiency, a self-inhaling structure cup segmented wheel is developed to generate internal cooling effect. The internal cooling technology is compared with traditional cooling conditions in the grinding experiments on TC4 （Ti-6Al-4V）. The results indicate that the self-inhaling internal cooling wheel can reduce the grinding surface temperature by 30% or more, and the grinding efficiency doubles. Utilizing water-based semi-synthetic coolant, the segmented wheel with the self-inhaling structure can further reduce the grinding temperature by about 50%.

内热源影响下高压电力电缆着火机制

为探究高压电力电缆因过载或短路且线芯发热影响下的着火机制,使用加热棒模拟电缆内部故障热源,并开展电缆着火试验,分析内热源功率及电缆线芯截面积对电缆温升、着火时间等着火关键参数的影响,发现电缆从被加热至着火到燃烧的全过程可分为初期加热、热解气体逸出、着火、燃烧及熄灭4个阶段。结果表明:绝缘层熔融物的滴落会导致火焰形态发生变化,电缆各结构层表面温度的升温速率随内热源功率的增加及与内热源表面距离的减小而增大,功率的增加弱化了电缆线芯截面积对各层升温速率的影响;电缆的着火时间与内热源功率呈线性递减的关系。

基于CFD的燃煤锅炉末级过热器壁温分布特性研究

针对燃煤锅炉高温受热面易发生超温和爆管事故的问题,综合考虑炉内烟气侧与管内蒸汽侧对受热面管壁温度的影响,基于数值模拟的方法简化了炉内煤粉气流的燃烧过程并构建了炉内烟—汽耦合换热模型,实现了对末级过热器沿程壁温的快速计算。在此基础上,探究了不同工况下该级受热面壁温分布特点及壁温峰值位置变化规律等。结果表明:受管外烟气与管内蒸汽的耦合影响,末级过热器沿程壁温基本呈双峰分布;随着负荷上升,烟道内不同管屏的沿程壁温分布曲线差异变小,烟道两侧管屏壁温峰值位置出现不同程度的下移。

Joint statistical-dynamical approach to decadal prediction of East Asian surface air temperature

A joint statistical-dynamical method addressing both the internal decadal variability and effect of anthropogenic forcing was developed to predict the decadal components of East Asian surface air temperature(EATs)for three decades(2010–2040).As previous studies have revealed that the internal variability of EATs(EATs_int)is influenced mainly by the ocean,we first analyzed the lead-lag connections between EATs_int and three sea surface temperature(SST)multidecadal modes using instrumental records from 1901 to 1999.Based on the lead-lag connections,a multiple linear regression was constructed with the three SST modes as predictors.The hindcast for the years from 2000 to 2005 indicated the regression model had high skill in simulating the observational EATs_int.Therefore,the prediction for EATs_int(Re_EATs_int)was obtained by the regression model based on quasi-periods of the decadal oceanic modes.External forcing from greenhouse gases is likely associated with global warming.Using monthly global land surface air temperature from historical and projection simulations under the Representative Concentration Pathway(RCP)4.5 scenario of 19 Coupled General Circulation Models participating in the fifth phase of the Coupled Model Intercomparison Project(CMIP5),we predicted the curve of EATs(EATs_trend)relative to1970–1999 by a second-order fit.EATs_int and EATs_trend were combined to form the reconstructed EATs(Re_EATs).It was expected that a fluctuating evolution of Re_EATs would decrease slightly from 2015 to 2030 and increase gradually thereafter.Compared with the decadal prediction in CMIP5 models,Re_EATs was qualitatively in agreement with the predictions of most of the models and the multi-model ensemble mean,indicating that the joint statistical-dynamical approach for EAT is rational.

多相混输泵用超高压机械密封性能研究

针对超高压混输泵机械密封易磨损失效的问题,介绍了端面槽加工和涂层应用两种策略,用热流固耦合分析方法,分析了浅槽微接触式机械密封在实际应用中的温度分布和端面变形情况,阐述了表面涂层技术的应用,进行了一系列机械密封性能的试验研究。研究结果不仅证实了这些技术在提高机械密封寿命和可靠性方面的有效性,还证实了端面开槽和涂层技术在降低摩擦、改善耐磨性能方面的显著效果。为超高压混输泵机械密封系统的设计和优化提供了重要的理论依据及实践指导。

基于蒙特卡洛法旋翼飞行器红外辐射特性研究

小型旋翼飞行器的广泛使用给高价值目标安全带来了全新挑战。为了有效探测与防御小型旋翼飞行器,研究小型旋翼飞行器红外辐射的空间分布特性具有重要意义。首先,针对某小型旋翼飞行器,建立了飞行器的几何模型,并对模型进行非结构化网格划分,生成面网格,确定每个面网格的面积和方向矢量;其次,分别对静态、空载飞行10 min和挂载100 g载荷飞行10 min三种工况条件下的旋翼飞行器,进行了温度测量和红外辐射图像采集;最后,基于蒙特卡洛法,考虑辐射网格单元对光束的吸收和反射,计算了旋翼飞行器在不同工况条件下不同探测方向的中远红外辐射强度分布及其规律。测试与计算结果表明,旋翼电机和电池是飞行器的主要红外辐射源;旋翼飞行器飞行时间越长,载荷越大,其红外辐射就越强;在天顶角θ为78°、101°和160°左右方向上,旋翼飞行器的辐射强度呈现峰值,而在天顶角θ为0°、90°和180°方向上,辐射强度较小;旋翼飞行器辐射主要集中在长波红外波段。

集中生活热水系统循环流量有关问题研究

梳理了不同版本建筑给水排水设计标准对生活热水管道热损失计算的有关规定,以及相关设计手册、标准图集等对生活热水管道热损失计算的方法,参考国家标准《工业设备及管道绝热工程设计规范》(GB50264-2013)的有关规定,对生活热水管道热损失的计算方法进行研究,并就有关问题提出了看法。

非等温工况下电缆线芯温度快速计算方法

现有电缆线芯温度快速计算方法不适用于电缆外表面为非等温面的工况,为对该工况下电缆线芯温度进行快速计算,基于有限元法研究了电缆线芯温度随表面温度不均匀性的变化规律。结果表明电缆外表面平均温度一定时,线芯温度不随电缆外表面温度分布的变化而变化,并基于热网络法进行理论分析证明了规律的普适性。在计算线芯温度时,可将电缆外表面视为等温面,沿用现存热路模型进行快速计算,其中等温面温度采用外表面温度平均值代替。

接触式机械密封端面平均温度耦合计算方法

研究接触式机械密封端面平均温度与端面摩擦因数相耦合的计算方法问题。将机械密封环简化为等截面当量筒体,推导出了接触式机械密封端面平均温度的计算式,给出了密封环简化为当量筒体的具体方法;基于分形理论,建立了接触式机械密封端面摩擦因数计算模型。考虑端面平均温度与端面摩擦因数的相互耦合关系,提出了端面平均温度的具体计算方法。通过模拟计算,对B104a-70型机械密封端面平均温度的影响因素进行了分析。结果表明,端面平均温度随着弹簧比压或密封流体压力的增大,线性地增大;随着转速的增大,近似线性地增大,且端面越光滑,线性越好,增大的幅度也越大;随着端面分形维数的增大或特征尺度系数的减小,非线性地增大,当端面较粗糙时,端面平均温度的变化较小;当端面较光滑时,随着端面分形维数的增大或特征尺度系数的减小,端面平均温度迅速增大。

屋顶绿化隔热等效热阻

针对自然气候作用下的草地式屋顶绿化形式,提出采用屋顶绿化隔热效果实测与屋顶热传导计算分析相结合的方法确定绿化层等效热阻,并在重庆选择通风屋顶有绿化层和无绿化层的实例进行了连续5个月的夏季隔热效果现场实测,结果表明:气温越高、太阳辐射越强,屋顶绿化层的隔热效果越好。实测数据的理论分析得到屋顶绿化层的等效热阻为0.56 m2.K/W。

采用Laplace方法的单芯电缆线芯温度动态计算

电缆线芯温度是电缆安全运行的重要参数。针对电缆线芯温度难于实时监测的问题,结合电缆传热学原理,提出基于电缆实际运行电流和表面温度计算电缆线芯温度的方法。首先建立电缆线芯温度动态计算的热路模型,进一步推导出计算电缆线芯温度的Laplace热路模型;然后剖分连续运行电流为阶跃输入值,并代入基于集中参数法所建立的Laplace热路模型,从而实现连续变化电流作为电缆线芯温度计算的实时输入量。通过试验研究和误差分析,基于电缆表面温度和实际运行电流实时计算线芯温度方法可以满足线芯温度实时监测,进一步研究分析能够实现载流量预测。

不同建筑材料猪舍围护结构的夏季隔热性能研究

为了寻找夏季隔热效果良好的猪舍围护结构材料,对北京市某猪场的猪舍和部分附属用房的吊顶、东墙和西墙内表面温度、舍内、舍外温度进行了监测。监测结果表明,试验期间,彩钢夹芯板屋顶+单层彩钢板吊顶、平面钢筋混凝土楼板屋顶+石膏板吊顶和彩钢夹芯板屋顶+PVC吊顶的内表面温度的最高值分别为35.3℃、32.8℃和31.2℃;24砖墙+外保温(5cm厚岩棉)东墙、24砖墙东墙和空心水泥板(10cm)+单层彩钢板(空气层17cm)东墙的内表面温度最高值分别为30.1℃、30.7℃和36.0℃;24砖墙+外保温(5cm厚岩棉)西墙、24砖墙西墙、空心水泥板(10cm)单层彩钢板(空气层17cm)西墙和单层彩钢板西墙数值分别30.2℃、31.1℃、38.8℃和44.7℃;24砖墙+外保温(5cm厚岩棉)+彩钢夹芯板屋顶+单层彩钢板吊顶和24砖墙+彩钢夹芯板屋顶+单层彩钢板吊顶的舍内温度最高值分别为35.5℃和36.0℃。在北京地区,24砖墙+外保温(5cm厚岩棉)+彩钢夹芯板屋顶+单层彩钢板吊顶和24砖墙+彩钢夹芯板屋顶+单层彩钢板吊顶的建筑形式都能起到一定的夏季隔热的作用,符合夏季猪舍隔热设计要求,两种建筑形式内的夏季最高温度均超过各阶段猪的高临界温度。

屋顶绿化内表面对太阳辐射的反应特性

利用屋顶绿化内表面温度夏季测量数据进行热惰性统计分析,提出了实际气候作用下衰减性和延迟性的评价方法。结论表明绿化屋面对室外热作用的衰减性比无绿化屋面提高了近一倍,内表面温度变化受太阳辐射影响小于无绿化屋面。

倒丁字型混凝土结构施工期温控与防裂研究

针对倒丁字型混凝土结构特点以及施工期易产生裂缝这一问题,阐述了该类型混凝土结构裂缝的产生机理,提出了表面保温、水管冷却、吊空模板等温控防裂技术。运用混凝土温度场和应力场的基本原理和三维有限单元法,对某实际工程下进行了仿真计算分析。计算结果表明在表面保温和内部水管降温相结合的温控措施下,防裂效果良好。该措施对类似工程具有一定的参考价值。