辅助热箱-热流计法在建筑物围护结构热阻现场检测中的应用

讨论采用"辅助热箱-热流计法"检测建筑物围护结构的热阻,实现非采暖季的检测。由于检测面大量广,检测方法必须相对简便易操作,据此原则提出:对于热箱法中由于侧向热流引起的误差,采用把在两侧测得的热流值加权平均的方法加以修正,以实现现场测试的基本精度。根据建筑围护结构检测的特定情况,用数值模拟的方法归纳总结出适用于不同保温形式的围护结构加权平均系数,即修正系数。通过对近几年来大量检测结果与理论值的分析,这种检测和数据处理方法可以满足对于建筑围护结构热工性能现场检测的要求。     

太阳辐射对围护结构热流密度的现场检测误差分析

围护结构表面温度和热流密度现场检测是建筑节能检测的主要内容,也是正确评价建筑围护结构节能与否的基础计算指标。为正确评价太阳辐射对围护结构热流密度检测的影响,准确计算和修正热流密度检测指标结果,对广州地区的太阳辐射引起的热流密度检测误差进行了分析研究,定量计算了不同朝向太阳辐射引起的检测误差,提出了由于太阳辐射引起的检测误差控制指标。     

热箱法现场检测建筑物围护结构热阻的探讨

现场检测建筑物围护结构的热阻对于贯彻国家的建筑节能法规有重要意义。本文提出采用热箱法检测建筑物围护结构的热阻以解决非采暖季进行检测的问题。利用所建立的传热模型和数值计算软件,通过对热箱法现场检测建筑物围护结构热阻时由于侧向热流引起误差的分析,讨论了各参数对这种测试方法的影响;研究表明该方法是可行的,但应对侧向热流引起的误差给予足够的重视,必要时应采取适当措施加以修正。     

围护结构传热系数的现场检测装置及实践

本文详细介绍了自制现场检测围护结构热阻的装置以及检测步骤和数据处理方法,通过标准墙体的对比试验确定加热箱半径和测试系统的修正系数,并通过实践应用验证了该测试装置用于现场检测围护结构传热系数的可行性及准确性。     

控温箱-热流计法检测墙体传热系数的误差分析及修正方法研究

建筑物墙体热工性能检测是建筑节能工程验收的必要环节,而控温箱-热流计法是近年来提出的较实用的现场检测方法。本文阐述了控温箱-热流计法现场检测围护结构传热系数的方法及基本原理,对检测结果出现数据偏差的原因进行了分析,并提出相应的修正方法,包括建立基准板和引入修正系数;最后通过实例验证该修正方法的可行性,为将来测试数据的修正提供参考依据。     

在非采暖地区应用热箱-热流计法检测建筑围护结构热阻的探讨

采用控温箱一热流计法(简称热箱法),运用热流计法作为基本的检测方法.同时用热箱人工模拟采暖期的热工环境,实现建筑物围护结构传热系数检测,可避免热流计法受季节限制的问题.采用热箱法对某建筑物外墙传热系数在不同环境条件下进行检测,分析了检测数据的可靠性和实用性以及气候条件、太阳辐射、侧向热流等因素对围护结构传热系数的影响.实测结果表明,在非采暖地区应用热箱法进行建筑物围护结构传热系数的现场检测是可行的,应用时需要尽量避免环境因素和侧向热流对检测结果的影响.     

关于建筑物围护结构传热系数现场测定方法的思考

围护结构的传热系数是考察建筑节能的评估方法之一,本文通过研究发现目前国内用于建筑物主要部位传热系数现场检测的仪器和方法存在的问题。问题一,我们在现场测量中应用的热箱法因为仪器本身功率无法连续可调,所以根据功率换算出的传热系数测量精度低,误差大：问题二,通过实验发现国内研制的热流传感器测定的误差可能会高达15％以上。因此,为了解决围护结构的传热系数现场测试的问题,应开发高精度热流计,以替代目前的现场测试仪器;同步开展非稳态法测量传热系数的研究。     

围护结构冷负荷快速计算方法研究

本文提出了一种围护结构冷负荷快速计算方法,即以冷负荷系数法为基础,将建筑外围护结构视为一个整体,通过计算冷负荷修正系数而得到围护结构冷负荷。文中定义冷负荷修正系数为围护结构冷负荷与外围护结构冷负荷之比,同时还提出了冷负荷修正系数的计算方法。在计算建筑围护结构部分冷负荷时,只需用建筑外围护结构部分冷负荷乘以冷负荷修正系数即可,不用特殊计算内围护结构部分的冷负荷。根据围护结构冷负荷快速计算这一方法,以Access和VBA为工具编程,制作了一个冷负荷快速计算软件。该软件省去了普通软件逐个房间计算冷负荷的复杂性,同时也避免了用冷负荷指标估算时的误差。最后依次采用冷负荷快速计算软件以及现有的常用负荷计算软件计算典型建筑的冷负荷,验证该软件的准确性和可行性。     

西藏节能建筑围护结构传热系数朝向修正

针对现行供暖居住建筑节能设计标准应用于西藏地区存在有供暖能耗指标却没有完整的能耗计算基本参数,即没有围护结构传热系数的朝向修正系数的问题,以拉萨典型气象年气候参数为依据,采用反应系数法对围护结构各部分供暖负荷进行了动态模拟计算,得到了围护结构各朝向修正系数,对南窗传热系数提出了变系数修正方法。     

关于自平衡法中侧阻力修正系数的讨论

国内现行的部分自平衡法规范中,承载力计算时采用的修正系数是抗拔系数按土层厚度的加权平均确定的。本文结合现场试验对此进行了探讨,提出了抗拔系数按土层厚度和摩阻力经验值的联合加权平均的算法,可降低计算误差,提高桩侧摩阻力的检测精度。     

Measuring incident radiant heat flux using the plate thermometer

This paper shows that the plate thermometer as described in the fire resistance test standards ISO 834-1 and EN 1363-1 can be used for measuring incident radiant flux under ambient conditions as an alternative to water cooled total flux heat metres (HFMs). Measurements with a plate thermometer mounted in the cone calorimeter and exposed to different heat flux levels were analysed as well as simultaneous measurements with total HFMs and plate thermometers in large scale tests. It is shown how the incident radiant flux to a target can be derived from measurements with total HFMs and plate thermometers, respectively, and how well these two methods match. The plate thermometer is therefore deemed to be a practical alternative for measuring thermal conditions including incident radiant heat flux particularly under field conditions. It is, however, recommended that the plate thermometer should be modified when used under ambient conditions to reduce errors.     

岩土热物性集总热阻计量模型及其求解体系

由于地埋管周围岩土体状况的复杂性及由此导致的回归分析时统计性误差影响等原因,根据现有岩土热物性传热模型及热响应试验不能精确求解岩土热物性。探讨了消除解释变量性质影响的岩土集总热阻分析方法,并通过计量学误差分析体系进一步建立了岩土集总热阻计量模型,摆脱了相关不确定扰动的复杂影响,将这一传热问题转变为热工计量分析问题,根据逐时集总热阻即可计算出在各种进出口温度及初始土壤温度条件下的逐时单位管长换热量。以多个工程实测结果验证了该模型及其求解体系的有效性。     

Error analysis of in situ field tests of fenestration net energy performance

The need for information about fenestration net energy performance under realistic conditions is discussed and the method of measuring it in a “field test” on a complete building is reviewed. A detailed consideration of the energy flows entering the energy balance on a building space adjacent to a fenestration system and the effect of random measurement errors on the determination of fenestration performance is presented. Estimates of the error magnitudes are made for prototypical field tests utilizing a residential and a moderate-sized commercial building. In both cases, it is shown that these errors make it difficult to isolate the fenestration performance even for relatively low-performance windows (1 – 2 times the resistance of single glazing). It is concluded that whole-building measurements are not well adapted to measuring the performance of advanced fesestration system (thermal resistance 2 – 10 times that of single glazing or shading coefficient less than 0.7).     

Numerical method for evaluating the lateral resistance of sleepers in ballasted tracks

Ballasted track sleepers have the important function of providing sufficient lateral resistance to prevent the lateral movement of rails. If the lateral force induced by the thermal expansion of steel rails overcomes the lateral resistance of sleepers, rail buckling may occur. More attention has been paid to this problem of lateral stability since the introduction of continuous welded rails. However, there is a high degree of uncertainty in the prediction of the lateral resistance of sleepers. In view of the foregoing, a series of laboratory tests was conducted on 1/5-scale models to evaluate the lateral resistance of sleepers. Single-sleeper pullout tests and track panel pullout tests were conducted on different types of concrete sleepers. The results of the pullout tests revealed the effects of the sleeper shape, the sleeper spacing, and the number of sleepers on the lateral resistance. Based on the model test results, a new numerical method for evaluating the lateral resistance of sleepers is proposed.     

Comparison of the thermal performance of double U-pipe borehole heat exchangers measured in situ

A borehole heat exchanger is a ground heat exchanger devised for the extraction or injection of thermal energy from/into the ground. The thermal performance of a borehole heat exchanger can be assessed with a response test. The response test method allows the in situ determination of the thermal conductivity of the ground in the vicinity of a borehole heat exchanger, as well as the effective thermal resistance of this latter.The response test method is briefly described before it is applied to several designs of double U-pipe borehole heat exchangers. The tests have shown the viability of the method. They reveal that the thermal resistance can be decreased by 30% when quartz sand is used instead of bentonite and when spacers are used to keep the plastic pipes in contact with the borehole wall. With a common heat extraction rate of 50 W/m of borehole length, the temperature gain in a heat pump evaporator is +2 K. Finally, a mobile device has been developed to offer the possibility of accomplishing a response test.     

渤海湾软黏土对埋设海底管线约束力的研究

海底管线与地基土体的相互作用在管线设计中至关重要,针对海底管线在温度应力下发生整体屈曲变形时可能产生的竖直向上、水平向及轴向运动,研究地基土体对管线的约束力。结合渤海湾海底地表土质特点选取软黏土开展室内管土相互作用试验,研究不同直径、不同埋置率（上覆土厚与管线直径的比）的管线竖直向上运动、水平向运动以及轴向运动时土体抗力的发挥过程,采用数值方法对模型试验进行模拟,进而将模拟方法扩展应用于对实际工程管线的模拟分析。试验结果表明与管线轴向运动相比,当管线发生竖直向与水平向运动时,其所受土抗力的大小受到管线直径与埋置率的影响显著;综合室内试验数据及数值模拟分析结果,提出了黏土对管线最大约束力及达到最大约束力所需位移的计算公式。     

Improvement of a measurement system for solar heat gain through fenestrations

This paper presents a study on the improvement of a system for measuring solar heat gain through fenestrations. The system allows the quantification of the thermal fraction that penetrates into a room through a fenestration due to solar radiation, and also the determination of the Solar Factor. To test and improve the functioning of the system, some field measurements and calibration of sensors (heat flux meters) were carried out. Initial measurements demonstrated that there was an error in the Solar Factor obtained and also that there was an increase in the temperature of the heat flux meter support plate. Currently the equipment uses a heat dissipation system with fans that insufflate air directly onto the rear side of the heat flux meter support plate. The increase in the temperature difference between the plate and the external air reduces the heat flow through the sensors, causing errors in the measurements. New tests were carried out using a cooling system with water circulation in a thermostatic bath. The decrease in the temperature difference between the heat flux meter support plate and the air provided good results, demonstrating the necessity for modifications to the currently used cooling system.     

Determination of specific heat capacity by transient plane source

A standard TPS measurement gives the thermal conductivity and thermal diffusivity of an isotropic material which in turn gives the heat capacity. The thermal properties of an anisotropic material can be measured if the heat capacity is known. A method for heat capacity measurement exists, where the TPS sensor is attached to a sample container which is surrounded by insulation. However, it's based on an assumption of negligible heat losses which leads to uncertainties in the results. From that position, this work aims to model the heat losses from the specific heat measurements with TPS. A new set-up is introduced, where the sensor with the container hangs freely in a steel tube to get more predictable heat losses. The results show that the measurements can be modelled as a network of lumps connected by conductances approximated as constant. Thereby, the conductances out from the system can be solved from a reference measurement and used as input for a model of a measurement with a sample. The model seems to underestimate the heat capacity, which might be a consequence of temperature dependent effects on the conductances from convection. The tube in the set-up could be evacuated to minimize those losses.     

钢筋混凝土柱低周疲劳全过程累积损伤性能简化分析方法

为了有效预测地震作用下钢筋混凝土柱的低周疲劳损伤累积程度与损伤后的剩余承载能力,提出了一种 基于单调荷载-位移关系并考虑低周疲劳效应的钢筋混凝土柱损伤承载能力简化分析方法。首先,根据自洽方法 并假设裂纹符合Weibull分布,提出了基于细观机理的混凝土损伤模型,给出了混凝土损伤指标与有效模量、应 变的定量表达式,并通过非线性数值分析得到了钢筋混凝土柱的单调荷载-变形曲线;然后,通过分析纵筋的塑 性低周疲劳损伤,建立了基于割线刚度的钢筋混凝土柱低周疲劳变形性能损伤计算模型,模型参数根据试验研究 获得,推导了柱割线刚度和抗力的衰减规律计算公式;最后,在以上工作的基础上,分析低周疲劳作用对钢筋混 凝土柱底截面混凝土和纵筋应变的累积增大效应,得到混凝土损伤后的有效弹性模量,提出了考虑低周疲劳损伤 后的钢筋混凝土柱承载能力和变形能力计算方法。编制非线性损伤分析程序,对损伤后试验柱进行了计算分析。 结果表明,该方法得到的计算值与试验值的相对误差处于合理范围之内,验证了该方法的可靠性和实用性。