Methodology for the calculation of response factors through experimental tests and validation with simulation

One of the most simple and intuitive methods employed to characterise a building solution in transient regime is based on the use of response factors. Its acquisition by calculation is an appropriate approach when the thermo-physical properties of the materials are known. However, in a great number of building products these data are not available and thus large errors in the calculation may be incurred, which cannot be quantified.In this work, a dynamic testing method is presented inside a guarded hot-box unit, where the response factors of a wall can be obtained without requiring the corresponding material properties.This method has been validated by means of a finite volumes simulation code for a wall which thermal characteristics are perfectly defined. Although the errors committed when adding the response factors and comparing them with the transmittance values are higher in the experiment than in the numerical analysis, there is a good agreement between the heat flows obtained experimentally and with the simulation.     

加气混凝土典型自保温墙体结露问题数值判断

加气混凝土自保温结构是建筑外墙自保温的重要结构形式之一,分析该种墙体热桥的内表面是否会发生结露现象是节能设计中不可缺少的计算环节.本文采用CFD软件Fluent,用有限体积法对南京地区冬季粉煤灰加气混凝土典型自保温墙体结构的传热过程进行了数值模拟计算,得到了典型结构内部的温度场,并得到如下结论:冬季时,加气混凝土自保温墙体内表面温度最低点均处于热桥部位室内表面宽度的中心处或阴角处,应重点考虑这些部位的结露问题;冬季时,各种加气混凝土自保温墙体内表面的最低温度均在13.5℃以上,高于室内空气的露点温度,不会出现结露现象.     

Topology optimisation of masonry units from the thermal point of view using a genetic algorithm

The aim of this work is to find an economic single leaf masonry wall for the building construction industry with minimised heat loss through the envelope. Lightweight aggregate concrete has the potential to offer weight reduction as well as good thermal and acoustic properties without significantly compromising the wall structural properties. The article presented here describes a search for the optimal topology of lightweight concrete masonry units according to normal thermal demands. The wall performance is measured through thermal transmittance values. The thermal behaviour of the units is calculated using three-dimensional finite element simulations. The developed topology optimisation method considers a numerical evolutionary algorithm iterating over the direct analysis performed by the finite element method. The obtained optimised topology unit will contribute towards sustainability and energy saving needs of today’s building construction industry.     

Steady-state heat transfer in an insulated,reinforced concrete wall: theory,numerical simulations,and experiments

In this paper, we focus on the steady-state heat transfer in an in situ constructed, insulated, reinforced concrete wall. The wall consists of two reinforced concrete slabs that sandwich an insulation layer. The two halves of the wall are joined by a series of steel wires to provide the needed structural integrity but unavoidably act as thermal shunts that increase the heat transfer rate. Nonetheless, the thermal performance of the wall surpasses that for an uninsulated wall because of the presence of the insulation. We compare the heat transfer rates predicted by a three-dimensional, numerical model with laboratory test data. The results from these data, and from numerous sensitivity studies performed with the model, show that the steady-state heat transfer in the wall may be approximated by the isothermal planes model. A more accurate estimate is obtained by a weighted average of the isothermal planes result and a simple parallel path model in which the isothermal-planes result is weighted by the factor 0.85. An appropriate value of the weighting factor, specific to a particular wall panel configuration, may be obtained using a correlation and graphical results that are presented in the paper. These quantitative results for the steady-state panel conductance are expected to be useful in exploring manufacturing strategies that would improve the thermal resistance of the panel, in designing energy-conserving buildings that employ such panels, and in establishing accurate energy standards and energy code compliance methods.     

Comparison of time series response factor estimators

It has long been recognized that thermal response factors offer an accurate way to describe the characteristics and performance of a building or of its components. Although the existing techniques use time series methods they need to have carefully controlled thermal conditions in order to achieve consistent results. In this work a novel method for estimating response factors is applied to unsteady times series temperature and heat flux data collected from a test cell. The novel response factor estimation method is based on new time series analysis techniques developed by the authors. The response factor values of a brick wall in the test cell are estimated using the novel method and using a standard time series analysis method. The U-value of the wall is the area under the response factors and the U-value determined from each method is compared with the theoretical value and the value obtained using the ratio of mean values method. The method extracts response factor values directly from the measured thermodynamic field values, and can be used to analyse linear or non-linear time invariant physical processes which experience stationary stochastic boundary conditions.     

底层墙体内饰面质量问题热工分析及防治

针对底层墙体内饰面常出现的质量问题 ,从建筑热工学角度分析了底层墙体热湿状况较差的根本原因 ,并提出改善和防治措施 ,对指导室内装修设计具有重要意义     

The influence of the external walls thermal inertia on the energy performance of well insulated buildings

Energy conscious building design consists in controlling the thermophysical characteristics of the building envelope such as, firstly, thermal transmittance (U-value). However, besides the U-value, the envelope thermal inertia should also be considered. The literature studies report very different estimations regarding the energy saving potential associated with the use of an adequate inertia, ranging from a few percentages to more than 80%. Therefore, this study aims at assessing the parameters enhancing or damping the role of thermal inertia, providing a variety of results. For this purpose several external wall systems with the same U-value but different dynamic properties were investigated to calculate the associated achievable energy savings. A parametric analysis was performed in progressive steps, by running the models of a virtual Test Cell and of a sample building. Both design parameters (heat transfer surface, solar control) and operational ones (ventilation rates, HVAC functional regime) were varied.It was found that the highest energy performance wall system has a proper combination of the dynamic thermal transmittance and thermal admittance values, although not necessarily the best ones. Moreover, it was shown that thermal inertia effects are enhanced if it is coupled with other energy saving measures and an efficient building use.     

自保温混凝土叠合承重墙结构体系研究

自保温混凝土叠合承重墙可以解决长期存在的传统建筑外墙保温的难题。这种墙体通过内贴保温层(聚苯板)的混凝土预制板,再和现浇混凝土柱连接而成。该墙体具有整体性好、施工快、保温隔热性好等特性。在弹性阶段,预制板和隐形框架可很好的协同工作,形成一个整体;弹塑性阶段,预制板随着裂缝的开展而逐步退出工作;墙体最后退化为由预制板边肋和隐形框架组成的密柱叠合框架;预制板和隐形框架两者可形成两道抗震设防。因此自保温混凝土叠合承重墙体具有较大的承载力、良好的抗震性能和延性。     

高效保温砌块砌体热工性能试验研究

某高效保温砌块是一种同时具有承重和保温功能的新型建筑材料,本文分别利用热流计法和热箱法对某高效保温砌块墙体的传热系数进行测试,并对试验的结果进行分析,根据相应国家规范得出该保温砌块砌筑的墙体满足严寒地区节能50％要求。     

间歇供暖时不同保温结构外墙的动态热响应特性实验研究

为了研究间歇供暖时不同保温结构外墙的动态热响应特性的基理,搭建了动态测试实验建筑,在同一外墙上构建了6种保温结构墙体和一种烧结实心砖参照墙体,实验以4种典型间歇供暖模式、在相同室内外环境条件下对比测试了7种外墙的内表面温度及热流。供暖启动初期内保温结构外墙的内表面温度上升迅速且内表面热流值较低,表明这种保温结构外墙动态热响应特性远优于其他6种外墙。通过实验研究可得越靠近室内复合低蓄能材料的保温结构外墙在间歇供暖时动态热响应越快,达到舒适的室内热环境时间越短,建筑节能效果更好。     

砖-粉煤灰砌块夹心复合墙体传热系数研究

为计算砖-粉煤灰砌块夹心复合墙体传热系数,分析其热工性能,进行了普通砖墙体、普通砖-粉煤灰砌块夹心复合墙体、再生砖墙体和再生砖-粉煤灰砌块夹心复合墙体的传热系数试验.依据普通砖、再生砖及粉煤灰砌块导热的基本机理,结合现有研究成果,给出了这几种材料的导热系数与温度、湿度的关系表达式,并提出了适用于工程设计的传热系数真实值计算方法.通过分析试件传热系数的试验值、理论值及真实值,证明真实值计算方法正确合理;用再生砖替代普通砖应用于砖-粉煤灰砌块夹心复合墙体同样能达到较好保温效果,这可为再生砖的应用及砖-粉煤灰砌块夹心复合墙体建筑节能细化设计提供依据.     

Investigation of the performance of a ventilated wall

The need for environmental friendly and energy efficient building design has stimulated the design of new facade technologies, including various configurations of double skin facades. This paper investigates the thermal performance of a ventilated wall, both for heating and cooling. A thermal analysis was carried out, paying special attention to the characterization of the heat convection resulting from the buoyancy-induced flow in the open air channel which proved to be a critical aspect of the ventilated wall's behaviour. An integrated thermal and air flow model for the entire system was developed. A model of the ventilated wall construction was developed with the ESP-r simulation program and checked against experimental data from a real-scale test cell facility.The thermal benefits of adding a radiant barrier layer were also investigated. The results showed that this layer was beneficial in terms of the energy performance of the construction. Also, the comparison between the experimental and simulation model results showed satisfactory levels of convergence with the exception of the night hours during the summer period. A sensitivity analysis was also undertaken in order to investigate the main factors and the extent of their effect on the temperature variation inside the ventilated facades.     

采暖居住建筑楼梯间的热工设计分析

随着节能标准的不断提高,楼梯间的热工设计也进一步加强.在实践中出现了对楼梯间内外墙重复保温的情况.通过建立热平衡方程,对多层空心黏土砖砌体结构住宅楼梯间在不同热工设计条件下的耗热量进行对比分析.分析结果表明:楼梯间不采暖,仅需加强楼梯问外围护结构的保温就可以得到良好的综合效益.     

冷桥对墙体平均传热系数的影响

本文基于控制容积法编制了平面温度场分析程序，利用该程序对普通住宅的一个典型开间墙体内部二维温度分布进行了模拟。把按二维温度分布计算出的墙体传热系数与按标准的一维面积加权方法计算的平均传热系数作比较，两者差别很大。可见冷桥对墙体传热的影响只有通过二维、三维的温度场模拟才能比较准确地反映出来。     

Detailed energy saving performance analyses on thermal mass walls demonstrated in a zero energy house

An insulated concrete wall system¹ was used on exterior walls of a zero energy house. Its thermal functions were investigated using actual data in comparison to a conventional wood frame system. The internal wall temperature of massive systems changes more slowly than the conventional wall constructions, leading to a more stable indoor temperature. The Energy10 simulated equivalent R-value and DBMS of the mass walls under actual climate conditions are, respectively, 6.98 (m² °C)/W and 3.39. However, the simulated heating energy use was much lower for the massive walls while the cooling load was a little higher. Further investigation on the heat flux indicates that the heat actually is transferred inside all day and night, which results in a higher cooling energy consumption. A one-dimensional model further verified these analyses, and the calculated results are in good agreement with the actual data. We conclude that the thermal mass wall does have the ability to store heat during the daytime and release it back at night, but in desert climates with high 24-h ambient temperature and intense sunlight, more heat will be stored than can be transferred back outside at night. As a result, an increased cooling energy will be required.     

幕墙框的传热系数计算方法

幕墙整体传热系数的计算是通过一个面积加权的方法求得的。而幕墙中框及各种面材传热系数需要分别进行计算,在框与面材之间存在一个边界,这个边界不仅存在室内外纵向的传热,还存在框与面材之间的横向传热。如何准确的考虑这个边界的传热,是幕墙传热系数计算的关键问题。本文着重讲述一套框的传热系数计算方法,使其充分考虑边界传热在幕墙传热中的影响,仅供大家借鉴参考。     

基于火炕的热水供暖火墙系统供暖效果研究

将火墙式火炕与热水供暖系统相结合,在火墙燃烧室的正上方加设集热器,在房间布置散热器,利用热水循环将火墙燃烧室的部分热量转移,供给其他无炕、无火墙房间.对加设热水系统后的火炕和热水系统的热工性能及室内热环境进行了实验研究.结果表明,该供暖系统在保证火炕房间供暖条件下,能够满足无炕、无火墙房间的短期供暖要求,并且提高了火炕的热舒适性;可以燃用各种生物质燃料,从而减少农村商品能的消耗.     

建筑节能墙体保温技术的研究

随着经济的快速增长,我国的能源短缺问题日益严重,节能工作成为现代社会面临的重要问题。化工企业的科技革新使得我国的建筑节能墙体保温材料成为了可能,这种材料的使用不仅符合绿色环保的要求,也降低了施工工艺的成本。本文以节能墙体保温材料出发,探讨了建筑节能墙体保温技术的实施类型,为新材料的运用提出了基础。     

A data analysis method for detecting wall thermal resistance considering wind velocity in situ

To improve the accuracy of data analysis methods for the field measurement of wall thermal resistance, a method considering wind velocity is presented through an analysis of both surface heat flux and temperature samples. This analysis method takes the wall heat transfer of linear system into account, simplifying the first order differential equation of wall transient response based on the nodes of the interior and exterior wall surfaces. An approximate solution has been proposed in the form of time domain interpolation. By applying the weighted residual method for the approximate solution, the data analysis method about temperature, heat flux, and wind velocity can be achieved.A transient heat transfer model of a wall was established applying the infinite difference method, by which the proposed analysis method was validated in this paper. Additionally, the heat flow meter experiment platform considering wind velocity was built, on which the proposed method, the mean method and the dynamic analysis method suggested by the international standard ISO 9869 were applied to the test wall under different wind velocities. The wall thermal resistance value obtained in our proposed method has proven to be in better agreement with that obtained for a steady state.     

CFD analysis of heat collection in a glazed gallery

A glazed gallery in most old buildings is a space located on the first floor (and/or higher floors), facing south and almost fully glazed. As a result of the large glazed area and the orientation of the gallery, its temperature is warmer than the exterior and, in cold weather, it is used both as a space to insulate the adjacent rooms and as a leisure area, among other applications. In the framework of the ARFRISOL project (Bioclimatic Architecture and Solar Cooling), a demonstration container has been constructed in northern Spain (Asturias) which includes, among other bioclimatic elements, a glazed gallery. This gallery is considered as an element of Bioclimatic Architecture that enables solar radiation to be collected and the energy obtained to be used to support the building's air conditioning system. It consists of a south-facing glazed exterior wall, an intermediate space or passage and a partially glazed interior wall. Dampers located in the floor and ceiling of the intermediate space and connected to the air ducts enable the air circulating inside the gallery to be heated or cooled, depending on the season of the year, before it is further conditioned and conveyed to the rooms. This paper focuses on the three-dimensional numerical simulation of the airflow inside the gallery. The aim is to obtain a model to evaluate the thermal energy obtained in this architectural feature, integrating the effect of certain variables, such as the incident solar irradiation, the outdoor temperature and the air flow rate circulating in the gallery.