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.

Experimental Investigation on the Bush Inner Surface Temperature of a High Speed Spiral Oil Wedge Sleeve Bearing

The temperature of bush inner surface temperature is measured by using infrared thermometer and transparent bearing,and temperature rise is measured by using thermocouple. The influence of rotating speed and axial location on the bush inner surface temperature is studied,and the influence of supply pressure and rotating speed on the temperature rise is analyzed. The results show the bush inner surface temperature and temperature rise of spiral oil wedge hydrodynamic bearing increase with the increase of rotation speed. In axial direction,the temperature is higher around the oil return hole. The temperature rise decreases with the increase of supply pressure. The highest temperature of bush inner surface and temperature rise are higher at higher speed,so the temperature rise is the fundamental reason which restricts the increase of rotation speed for high speed sleeve bearing.

On-Line Life Monitoring Technique for Tube Bundles of Boiler High-Temperature Heating Surface

High-temperature heating surface such as superheater and reheater of large-sized utility boiler all experiences a relatively severe working conditions. The failure of boiler tubes will directly impact the safe and economic operation of boiler. An on-line life monitoring model of high-temperature heating surface was set up according to the well-known L-M formula of the creep damages. The tube wall metal temperature and working stress was measured by on-line monitoring, and with this model, the real-time calculation of the life expenditure of the heating surface tube bundles were realized. Based on the technique the on-line life monitoring and management system of high-temperature heating surface was developed for a 300 MW utility boiler. An effective device was thus suggested for the implementation of the safe operation and the condition-based maintenance of utility boilers.

Calculation on inner wall temperature in oil-gas pipe flow

Based on the energy equation of gas-liquid flow in pipeline,the explicit temperature drop formula for gas-liquid steady state calculation was derived.This formula took into consideration the Joule-Thomson effect,impact of terrain undulation and heat transfer with the surroundings along the line.Elimination of temperature iteration loop and integration of the explicit temperature equation,instead of enthalpy energy equation,into the conjugated hydraulic and thermal computation have been found to improve the efficiency of algorithm.Then,the inner wall temperature of gas-liquid flow was calculated by using explicit temperature equation and inner wall convective heat transfer coefficient of mixed flow which can be obtained by liquid convective heat transfer coefficient and gas convective heat transfer coefficient on the basis of liquid holdup.The temperature results of gas-liquid flow and inner wall in the case example presented both agree well with those in professional multiphase computational software OLGA.

Experimental Study on Impingement Processes of Fuel Sprays on Biomimetic Structured Surfaces

To improve the controllability of the wall-wetting process after the fuel spray-wall impingement in internal combustion engines,the methods of laser etching,chemical etching and surface free energy modification are used to prepare biomimetic structured surfaces with different wettability.The impingement processes of diesel and n-butanol sprays on the walls under different conditions are experimentally investigated.As the surface oleophilicity increases,the spreading radius of wall-impinging sprays decreases.At about 5 s after the fuel injections,the fuel spray droplets hit the walls for the first time,and the secondary breakup and rebound occur.The mixture concentrations of different fuels hitting the various walls reach the peak value.Under a higher surface temperature,the peak value of the mixture concentration is mainly related to the heat flux to the fuel droplets in different boiling regimes from the metal surfaces.The concentration of the air–fuel mixture in the near wall region increases with increasing surface oleophilicity,increasing wall temperature and decreasing ambient pressure.Compared with diesel,n-butanol presents a higher air–fuel mixture concentration in the near wall region.

2022年7月内蒙古干旱半干旱区涝—旱转折事件的成因分析

2022年7月内蒙古中西部地区降水明显偏少,且呈前期偏多、后期偏少的涝—旱转折性分布特征,分析不同阶段环流分布差异和影响系统间的配置对进一步做好内蒙古汛期降水预测具有重要作用。利用内蒙古116站逐日降水量、国家气候中心130项气候指数、美国国家环境预报中心/国家大气科学研究中心(National Center for Enviromental Prediction/National Center for Atmospheric Research,NCEP/NCAR)逐日再分析资料和美国国家海洋和大气管理局(National Oceanic and Atmospheric Admin⁃istration,NOAA)逐月海表温度资料,分析2022年7月内蒙古中西部地区涝-旱转折事件的成因。结果表明:(1)2022年7月内蒙古中西部地区降水量严重偏少,为该地区1991年以来同期降水最少、气象干旱最为严重。(2)7月1—11日降水相对偏多,冷空气路径偏北且强度较弱,西太平洋副热带高压强度偏弱,位置偏北、偏西,冷暖空气在内蒙古中西部地区交绥,加之这一时段高空西风急流位置偏北,内蒙古中西部位于急流轴以南,有利于高层辐散和上升运动发展。7月12—31日降水明显偏少,环流经向度加大,冷空气活动路径偏南且强度增强,西太平洋副热带高压强度偏强且位置明显偏南,不利于水汽输送,加之高空西风急流位置偏南,内蒙古中西部位于急流轴以北,不利于高层辐散和上升运动发展;7月中旬后期至下旬高空西风急流南北向扰动偏强有利于激发东亚—西北太平洋经向遥相关波列,使得西太平洋副热带高压位置偏南从而导致降水偏少。(3)日本海至北太平洋西北部地区的海温异常是影响内蒙古中西部地区降水多寡的重要外强迫信号之一。2022年7月该海区海温异常偏高,其上空激发的气旋式环流减弱了南方暖湿水汽的经向输送,是导致内蒙古中西部降水由涝转旱的原因之一。

温度对环氧树脂沿面闪络特性的影响研究

特高压穿墙套管的绝缘问题是特高压输电技术研究的重点,在实际的工况中,由于内部及外部环境的影响,穿墙套管时常处于室温以上的环境温度中,导致绝缘性能受到一定程度的影响。为了研究交流和直流电压下环氧树脂闪络电压随温度的变化规律以及温度的影响机制,搭建了环氧树脂沿面闪络试验平台,测量在恒定气压的SF_(6)氛围中,环氧树脂在不同温度下的闪络电压,仿真分析了闪络电压的变化原因。结果表明:在25~70℃范围内,随着温度升高,环氧树脂的闪络电压出现先小幅下降后上升的现象,存在闪络电压的最小值。该现象是由气—固界面电场分布、SF_(6)气体临界场强和环氧树脂表面陷阱能级的共同作用导致。研究成果可以为特高压直流穿墙套管绝缘优化配置提供实验依据。

柴油喷雾撞击高温壁面的瞬态传热特性

通过瞬态测温技术对定容燃烧室中柴油喷雾撞击高温壁面的瞬态传热特性进行了研究.结果表明:初始壁面温度从250℃升高到550℃,壁面上传热模式由膜态蒸发转化为核态沸腾,进而转化为过渡沸腾,这种转化使表面热流密度和换热系数先增大后减小,且分别在440℃和400℃达到最大值.增大喷射压力、减小撞壁距离和环境温度有助于提高表面热流密度和换热系数.初始表面温度的升高增加了喷射压力和撞壁距离对传热特性的影响,但降低了环境温度的作用.以毕渥数和傅里叶数表示的量纲为1表面热流密度曲线形态高度相似,且揭示了喷雾撞击高温壁面过程中的内部传热机制.此外,建立了一种准确性高、适用壁面温度范围广的预测最大表面热流密度的量纲为1模型.

青海地区居住建筑外围护结构冬季传热过程研究

以青海地区居住建筑为研究对象,通过EnergyPlus模拟软件研究了不同传热系数和太阳辐射吸收系数下各朝向墙体内外表面温度的变化规律,并对其热流密度进行对比分析。结果表明:增大太阳辐射吸收系数能有效提高墙体外表面平均温度,减小传热系数能有效提高墙体内表面平均温度。太阳辐射吸收系数对南墙平均热流密度影响最大,其次为屋面,北墙最小;传热系数对北墙平均热流密度影响最大,其次为屋面,南墙最小。

盖挖法基坑开挖对临近桥梁桩基的影响研究

城市交通建设往往临近既有建筑结构,为了掌握盖挖法深基坑开挖对临近桥梁桩基的影响,依托之江路输水管廊及道路提升工程,建立数值模型并对工程现场展开监测,分析对比了基坑开挖导致的围护结构变形及桥桩变形规律。结果表明:围护结构最大位移出现在基坑北侧坑中坑开挖后,为6.14mm,最大位移深度随基坑开挖而下移,且坑中坑开挖完成后,其对侧围护结构变形反而减小,坑中坑开挖布置在敏感结构对侧时对临近结构具有一定控制效果;桥梁桩基最大沉降出现在首道混凝土支撑安装后,但随基坑开挖而逐渐减小,盖挖造成的沉降主要水平影响范围距围护结构约为12.71m,对邻近桥桩的影响主要发生在基坑开挖的早期阶段,各项变形均在安全范围内,且不均匀沉降控制效果明显。

预防墙面装饰性开裂的施工措施分析

为有效解决墙面装饰性开裂问题,提高建筑结构整体美观性,确保人们居住的安全性和舒适性,论文论述了墙面裂缝的类型及装饰层施工工艺,分析了装饰性开裂的规律、成因、发展趋势,并分别从原材料及施工工艺等方面提出了防止墙面装饰性开裂的施工措施。

复杂山区地表温度模拟及影响——以内蒙古大青山为例

地表温度(LST)是影响植物分布和生态系统过程的重要因素。本研究利用天气研究与预测模式(WRF)模拟大青山保护区的高时空分辨率LST,通过气象站点观测值和MODIS LST值对比验证模拟结果的准确性,并通过综合影响因素和单一影响因素分析LST与环境因子之间的关系。综合影响因素分析是基于区域模拟LST和区域环境因子进行的分析;单一影响因素分析是首先固定其他环境因子,然后分析LST和单一环境因子的关系。结果表明:模拟值与3个站点观测值相关系数均超过0.97(P<0.001),与MODIS LST空间相关性为0.73(P<0.05),表明WRF在山区有很好的实用性。经综合影响因素分析,年均LST与高程的相关性最大(R>0.97),与2 m气温和2 m水汽混合比次之(R>0.8),与植被覆盖度和坡度较小(R>0.3),其他因素影响微弱。经单一影响因素分析,在春夏秋冬4个季节,随高程升高LST下降速率分别为0.83 K·(100m)^(-1)、0.79 K·(100m)^(-1)、0.80 K·(100m)^(-1)、0.32 K·(100m)^(-1);坡度每增加10°,LST在春夏秋冬分别升高-0.05 K、0.17 K、-0.14 K、0.02 K;植被覆盖度每增加10%,LST在夏冬两季分别升高0.31 K、1.41 K,其他季节则没影响;坡向对4个季节平均LST的影响均为南>西南>东南>西>东>西北>东北>北;年均LST与2 m水汽混合比呈对数关系,与2 m气温呈指数关系。研究结果可为大青山自然保护区管理提供基础数据,也为山地研究提供可借鉴的方法。

FDM多工艺参数对PLA制件尺寸误差的影响

为探索熔融沉积快速成型技术(FDM)的工艺参数对聚乳酸(PLA)制件成型尺寸误差的影响规律,通过逆向数据采集方法对制件的长度误差、宽度误差、厚度误差进行测量对比,在4个单一工艺参数(外墙打印速度、外墙线宽、打印温度、打印层高)变化对尺寸误差影响分析的基础上,采用响应面法对筛选出的3个主要因素进行交互实验与分析。结果表明,长度误差受工艺参数的影响最大,其次是厚度误差,工艺参数对长度误差、宽度误差以及厚度误差的影响程度的排序均为:打印层高>打印温度>外墙线宽。

Inner wall running state monitoring for the main pipe of nuclear power

The heat conduction equation is solved in this paper under specific boundary conditions.The coefficients of the obtained distribution equation are simplified with the piecewise integral method.Then the associated model for the cylindrical thermal equipment is established.The relationship of the surface temperatures,the material properties and the inner wall state of the cylindrical thermal equipment is described in the associated model.This model is applied to the inner wall running state monitoring of the main pipe.A multi-channel distributed optical fiber temperature measurement system is designed to acquire the external surface temperatures of the main pipe.Then the associated model can be used to analyze the surface temperature data of the main pipe.The location and the physical dimension of the inner wall defect can be got.Therefore,the inner wall defect monitoring of the main pipe can be realized.The feasibility of this method is verified by experiment.This method also provides a theoretical basis for the real-time monitoring of the main pipe’s internal state.

Different Ablation Models for the Wall-plasma Interaction Process in Pulsed Plasma Thruster

Ablation excited by current pulses is a very critical physical process in pulse plasma thrusters(PPT).Its effects on wall-plasma interaction directly determine the PPT performances.In order to reveal the process of the ablated wall interaction with the discharge plasma in PPT,ablation models formulated by three different boundary conditions at the wall-plasma interface are studied.These are the two widely used high-speed evaporation models(Model-L and Model-M),and the recently developed Keida-Zaghloul model(Model-K)of the Knudsen layer that takes into account the internal degrees of freedom on the energy flux conservation.First,fundamental mechanisms of the three ablation models are clarified by comparative analysis in order to gain a comprehensive understanding of the wall-plasma interaction.Then,the applicability of different ablation models with the numerical solutions of LES-6 PPT is investigated in detail using magnetohydrodynamic(MHD)modeling.Results show that Model-L and Model-M are actually special cases of Model-K when a simplified jump conditions limited by high velocity at the vapor/plasma interface is used;A ratio of ablation rate in Model-L to that in Model-M is about 0.8at the same wall surface temperature,while it rises to 1 at different surface temperature determined by Model-L and Model-M in PPT.Even though Model-K solution requires significant computational time,it shows more accurate ablation feature for the wall-plasma interaction and possesses better computing precision of impulse bit during post-pulse which is useful for future studies of the late time ablation.

围护结构太阳辐射吸收系数对太阳能采暖建筑外墙热性能的影响

利用墙体热工系统理论,依据墙体传热的室外边界条件具有地区差异和表面特性差异的特点,选取拉萨、银川和西安作为代表性地区,通过以附加热阻百分率和附加热惰性指标为外墙表面热工参数的等效计算方法,讨论冬季采暖条件下改变太阳辐射吸收系数对南墙节能量和内壁面温度的变化规律。结果表明:增大南墙的太阳辐射吸收系数可有效增大节能量,但会小幅降低内壁面温度的稳定性,这种影响在太阳辐照度最高的拉萨地区最为显著,其次为银川和西安,且随着墙体传热阻和热惰性指标的增大,节能量和内壁面波动幅度对太阳辐射吸收系数的敏感性变小。

THERMAL PERFORMANCE OF FELT TYPE VEGETATED FACADE SYSTEMS IN A TEMPERATE CLIMATE DURING HEATING AND COOLING PERIODS

Using vegetated facade systems(VFS)as a sustainable solution for existing and new buildings and evaluating thermal performance of these sytems are not a new concept.However,there is a gap in literature about measuring thermal performance of VFS applied on an insulated wall.Also,in the research literature,there are few studies measuring thermal performance of felt type VFS in temperate climates,and data about the thermal performance of VFS during winter periods is still scarce.Thus,the aim of the present study is to measure the thermal performance of a felt type VFS applied on a thermal insulated existing wall that us located in Kocaeli,Turkey,under Csa climate conditions during heating and cooling periods.Test results indicate that the felt type VFS acts as a shading device and has a positive contribution to the thermal performance of building walls during a cooling period.In daytime when there is a high amount of solar radiation,felt type VFS decreased exterior surface temperatures of the insulated existing wall by a maximum of 24.4℃,32.2℃ and 37.2℃,in spring,summer and fall periods,respectively.Additionally,indoor air temperatures of the vegetated facade were lower than indoor air temperatures of the reference facade with the maximum difference of 1.8℃ during the cooling period.Also,test results indicate that the vegetated facade never dropped to below 0℃ while exterior surface temperatures of the reference facade dropped below 0℃ at nighttime in the winter period.Thus,it can be claimed that the felt type VFS behaves as a thermal buffer and enhances the thermal performance of the exterior wall of the existing building during heating periods at nighttime.As a conclusion,although differences between exterior surface temperatures of vegetated and reference walls were high,differences between interior surface temperatures of vegetated and reference walls were not meaningful.That is due to the fact that the existing building exterior wall assembly includes 5 cm thickness thermal insulation material which enhance the thermal performance of the brick wall.Finally,according to solar reflectance results,it can be claimed that vegetated facade systems have a positive effect on reducing urban heat island effect.

新型温度响应型蠕虫状胶束堵漏剂合成与评价

针对水泥浆在封堵大尺度裂缝或溶洞出现的浆体滞留性差无法有效封堵、固化选择性差伤害储层等典型缺陷,利用表面活性剂分子缔合蠕虫状胶束理论,以N,N-二甲基环己胺(DMCHA)和山嵛酸(BA)合成堵漏剂TDL,并采用傅里叶变换红外光谱仪和核磁共振仪对合成堵漏剂进行结构表征;将TDL与煤油形成堵漏工作液,使其与水接触发生相间自组装,采用小角度X-射线散射仪(SAXS)和设计的倒置承压装置以评价堵漏体系的壁面稳定性和承压能力。结果表明:红外光谱和核磁氢谱均发现R—COO—NH^(+)(CH_(3))_(2)—R′的特征结构显示,且原料无残留;堵漏体系在地层水-封堵剂界面之间形成层间距为123.20Å的液晶层状凝胶结构,单位质量封堵剂承压压强达到78 MPa,承压下稳定时间超过30 d;堵漏体系在温度低于65℃时稳定存在,高于80℃流动性好,失去封堵效果。新型响应型蠕虫状胶束堵漏剂对中低温漏失层具有良好的封堵性能,亦可作为水泥堵漏前置段塞以应对恶性漏失。

相变墙体构造对室内热稳定性影响分析

由于相变材料的合理利用,能够有效提高建筑的室内热稳定性,降低建筑物的能源消耗;不同的相变墙体构造,其室内热稳定性也不同。为研究徐州冬季工况下适宜的相变墙体构造,通过ANSYS workbench软件,针对3种不同构造的相变墙体,模拟了其传热过程,并对室内外表面温度进行了分析。结果表明:徐州冬季工况时,内侧相变墙体内表面最低温度升高了0.35℃,相较于外侧和夹心相变墙体,提升幅度明显,同时,内侧相变墙体内表面温度的波幅也明显降低,内侧相变墙体对室内温度的调节作用明显,冬季工况下室内热稳定性最优。

基于流固耦合的燃气冲刷烧蚀内膛特性分析

火炮发射时,火药燃气与身管间发生剧烈的传热传质作用是导致身管烧蚀的重要因素。为了研究某155 mm火炮中高温高压高速的燃气流对身管的烧蚀特性,采用CFD流固耦合方法,建立了发射过程中的身管非稳态流动传热模型,并根据炮钢在不同温度下的烧蚀特点,将烧蚀过程分为热化学烧蚀和熔化烧蚀,建立了分段烧蚀模型。计算结果表明,身管内壁温度随时间的增加先迅速增大,随后逐渐降低。整体上,内壁温度随身管轴向距离的增大而逐渐降低。身管膛线起始区域的壁面温度最高,其烧蚀是熔化和热化学烧蚀共同导致的,而线膛部的大部分区域仅发生了热化学烧蚀。总烧蚀量随着身管轴向距离的增大而逐渐降低,膛线起始部的烧蚀最为严重,单发总烧蚀量(常温)为5.06μm。同时分析了不同工况对身管烧蚀特性的影响,发现最大烧蚀量与初始壁面温度呈现很强的正相关性,温度的升高会加剧身管的烧蚀。