Development of experimental study on coupled heat and moisture transfer in porous building envelope

A new facility was presented which can expediently and cheaply measure the transient moisture content profile in multi-layer porous building envelope.Then,a common multi-layer porous building envelope was provided,which was constructed by cement mortar-red brick-cement plaster.With this kind of building envelope installed in the south wall,a well-controlled air-conditioning room was set up in Changsha,which is one of typical zones of hot and humid climate in China.And experiments were carried out to investigate the temperature and moisture distribution in multi-layer building envelope in summer,both in sunny day and rainy day.The results show that,the temperature and humidity at the interface between the brick and cement mortar are seriously affected by the changes of outdoor temperature and humidity,and the relative humidity at this interface keeps more than 80% for a long-term,which can easily trigger the growth of mould.The temperature and humidity at the interface between the brick and cement plaster change a little,and they are affected by the changes of indoor temperature and humidity.The temperature and humidity at the interface of the wall whose interior surface is affixed with a foam plastic wallpaper are generally higher than those of the wall without wallpaper.The heat transfer and moisture transfer in the envelope are coupled strongly.

Comparative Experimental Study on Heat Transfer Characteristics of Building Exterior Surface at High and Low Altitudes

The external surface heat transfer coefficient of building envelope is one of the important parameters necessary for building energy saving design,but the basic data in high-altitude area are scarce.Therefore,the authors propose a modified measurement method based on the heat balance of a model building,and use the same model building to measure its external surface heat transfer coefficient under outdoor conditions in Chengdu city,China at an altitude of 520 m and Daocheng city at an altitude of 3750 m respectively.The results show that the total heat transfer coefficient(h_(t))of building surface in high-altitude area is reduced by 34.48%.The influence of outdoor wind speed on the convective heat transfer coefficient(h_(c))in high-altitude area is not as significant as that in low-altitude area.The fitting relation between convection heat transfer coefficient and outdoor wind speed is also obtained.Under the same heating power,the average temperature rise of indoor and outdoor air at highaltitude is 41.9%higher than that at low altitude,and the average temperature rise of inner wall is 25.8%higher than that at low altitude.It shows that high-altitude area can create a more comfortable indoor thermal environment than low-altitude area under the same energy consumption condition.It is not appropriate to use the heat transfer characteristics of the exterior surface of buildings in low-altitude area for building energy saving design and related heating equipment selection and system terminal matching design in high-altitude area.

Simulation of roof snow loads based on a multi-layer snowmelt model:Impact of building heat transfer

To investigate the impact of building heat transfer on roof snow loads,roof snow loads and snow load thermal coefficients from 61 Chinese sites over a period of 50 years are simulated based on basic meteorological data such as temperature,humidity,wind speed,and precipitation,and a multi-layer snowmelt model considering the building heat transfer.Firstly,the accuracy of the multi-layer snowmelt model is validated using the data of observed ground snow load and roof snow melting tests.The relationship between meteorological conditions,snow cover characteristics,and thermal coefficients of snow loads in three representative sites is then studied.Furthermore,the characteristics of thermal coefficients in each zone are analyzed by combining them with the statistical results of meteorological data from 1960 to 2010,and the equations of thermal coefficients in different zones on indoor temperatures and roof heat transfer coefficients are fitted separately.Finally,the equations in this paper are compared with the thermal coefficients in the main snow load codes.The results indicate that the snowmelt model using basic meteorological data can effectively provide samples of roof snow loads.In the cold zone where the snow cover lasts for a long time and does not melt easily,the thermal coefficients of the snow loads on the heating buildings are lower than those in the warm zone due to the long-term influence of the heat from inside the buildings.Thermal coefficients are negatively correlated with indoor temperatures and roof heat transfer coefficients.When the indoor temperature is too low or the roof insulation is good,the roof snow load may exceed the ground snow load.The thermal coefficients for heated buildings in the main snow load codes are more conservative than those calculated in this paper,and the thermal coefficients for buildings with lower indoor temperatures tend to be smaller.

Thermal performance of integration of solar collectors and building envelopes

The integration of building with solar collector was studied. The theoretical model of integration of building envelopes and flat plate solar collectors was set up and the thermal performance of integration was studied in winter and summer,and compared to envelopes without solar collectors. The results show that the solar collection efficiency is raised in the integration of building envelopes and solar collectors with the air layer doors closed. This is true whether in winter or summer. The increment is higher as the inlet water temperature increases or the ambient temperature is low. In winter,the heat loss is significantly reduced through integration of the building envelopes and solar collectors with the closed air layer doors. The integration with the open air layer door is worse than that without collectors. In summer,the heat gains of the integration of envelopes and solar collectors are more obviously reduced than envelopes without collectors,the integration with the open air layer door is a little better than the closed one,but the difference is very small.

Simulation of the Hygrothermal Behavior of a Building Envelope Based on Phase Change Materials and a Bio-Based Concrete

Phase Change Materials(PCMs)have high thermal inertia,and hemp concrete(HC),a bio-based concrete,has strong hygroscopic behavior.In previous studies,PCM has been extensively combined with many materials,however,most of these studies focused on thermal properties while neglecting hygroscopic aspects.In this study,the two materials have been combined into a building envelope and the related hygrothermal properties have been studied.In particular,numerical studies have been performed to investigate the temperature and relative humidity behavior inside the HC,and the effect of adding PCM on the hygrothermal behavior of the HC.The results show that there is a high coupling between temperature and relative humidity inside the HC,since the relative humidity changes on the second and third days are different,with values of 8%and 4%,respectively.Also,the variation of relative humidity with temperature indicates the dominant influence of temperature on relative humidity variation.With the presence of PCM,the temperature variation inside the HC is damped due to the high thermal inertia of the PCM,which also leads to suppression of moisture evaporation and thus damping of relative humidity variation.On the second and third days,the temperature changes at the central position are reduced by 4.6%and 5.1%,compared to the quarter position.For the relative humidity change,the reductions are 5.3%and 5.4%on the second and third days,respectively.Therefore,PCM,with high thermal inertia,acts as a temperature damper and has the potential to increase the moisture buffering capacity inside the HC.This makes it possible for such a combined envelope to have both thermal and hygric inertia.

Impact of light-weight external thermal insulation materials on building surrounding thermal environment in summer

The method for calculating wall surface heat storage coefficient was introduced,and the coefficients of several common walls with light-weight external thermal insulation materials and the traditional solid clay brick wall were calculated.In order to study the impact of light-weight external thermal insulation materials,a contrasting experiment was carried out between an external insulated room and an uninsulated room in August,2010,in Chongqing,China.The result shows that outside surface heat storage coefficient of the insulated wall is much less than that of the traditional wall.However,during sunny time,the surface temperature of external walls of the insulated room is obviously higher than that of the uninsulated room.In different orientations,due to different amounts of solar radiation and being irradiated in different time,the contrasting temperature difference(CTD) appears different regularity.In a word,using light-weight external thermal insulation materials has a negative impact on building surrounding thermal environment and people's health.Finally,some suggestions on how to eliminate the impact,such as improving the surface condition of the building envelop,and plating vertical greening,are put forward.

Research on Thermal Insulation and Energy Saving of External Wall in City High-rise Building of Cold Area

This paper applies the method of numerical simulation and field detection, and studied energy-saving insulation characteristics on the external wails of high-rise buildings in cold area, analyze and recommend the best arrangement of building and the most generous exterior wall insulation system suitable for cold area, and the degree of insulation materials were studied. The results show that： the mode preferred cold area is exterior insulation, insulation material made of extruded polystyrene board, frame structure filling wall preferred ceramsite hollow block.

A New Type of Paper-frame Cavernous Material and Its Application in Energy Efficiency in Buildings

This paper introduces a new type of paper-frame cavernous material, which is a made-up hollow material, by using silicate-cinder size to drench and daub. It possesses excellent performances such as light-weight, high-intensity, fire-resistance, sound-insulation, heat-insulation and no-pollution. Composed with concrete materials, a new type of bearing and energy-efficient block can be gained, which is kind of excellent wall materials and has a wide application prospect.

夏热冬冷地区办公建筑节能改造设计研究

本文主要探究了夏热冬冷地区某办公建筑的节能改造设计方案。调查发现,该办公建筑一天之中8-18时能耗较高;一年之中夏季能耗最高,冬季次之;空调能耗在总能耗中的占比最大。基于实用性和经济性原则,选择建筑围护结构进行了节能设计,外墙方面使用EPS保温板,屋顶设计成种植屋面,外窗改造成真空玻璃窗和双层玻璃幕墙。结果表明,相比于原建筑,使用节能设计方案后外墙、屋顶和外窗的传热系数均有大幅度的降低,使得建筑保温隔热性能明显提升,达到了节能降耗的效果。

高层胶合木结构建筑气密性测试研究

我国作为人口大国,人均能源资源占有量低,每年的能源消耗数额巨大,其中建筑能耗所占比重极大。为进一步控制具有低碳环保的天然优势的木结构建筑运行能耗,以一栋6层胶合木梁柱框架-轻型木结构剪力墙建筑为研究对象,通过围护结构传热系数与建筑气密性能的现场测试,对其建筑能耗展开研究。结果表明:该大楼建筑能耗使用情况符合中小型办公楼能耗现况,且建筑得热主要因太阳辐射,建筑失热主要因围护结构热传导所致。建筑气密性能对该大楼的能耗影响最大,其次为地理位置,而建筑结构类型与窗墙比对建筑能耗影响较小。

广西居住建筑围护结构线性热桥数值模拟研究

为研究广西居住建筑不同保温方式的线性热桥对围护结构热工性能的影响,以某剪力墙结构的住宅建筑为例,应用BECS节能设计软件,对典型线性热桥的线传热系数和案例建筑的外墙热工性能进行数值模拟和分析。结果表明,线性热桥对墙体传热的影响显著,在外墙平均传热系数中因线性热桥所致的外墙平均传热系数分项约占1/3;当外墙采用内保温时,外墙与内墙、外墙与垂直外挑楼板部位的线传热系数最大,其次是外墙与楼板、外墙与水平外挑楼板部位;当外墙采用外保温时,外墙与垂直外挑楼板部位的线传热系数最大,其次是门窗上口、下口、左右口及外墙与水平外挑楼板部位。同时发现,不同保温方式的线性热桥对外墙平均传热系数的影响程度不同,内保温方式的线性热桥对外墙平均传热系数的影响高于外保温;且保温材料越厚,线性热桥对外墙平均传热系数的影响越大。

寒冷地区外窗热工性能对建筑采暖空调负荷的影响

【目的】通过研究外窗热工性能对建筑采暖空调负荷的影响,得出各项外窗热工性能参数对建筑节能效果的影响程度,有助于提升建筑的节能效果。【方法】利用DeST-h,建立寒冷地区(郑州)75%节能标准居住建筑基本模型,以太阳得热系数、窗墙比、外窗传热系数为变量进行单因素影响计算,以窗墙比和太阳得热系数、建筑层数和太阳得热系数为变量进行多因素分析,研究太阳得热系数、窗墙比、外窗传热系数对建筑采暖空调负荷的影响。【结果】结果表明,窗墙比、传热系数对建筑采暖空调负荷影响趋势明显,均呈正相关;太阳得热系数对建筑采暖空调负荷影响趋势与建筑窗墙比、建筑层数有关。【结论】建筑外窗节能应优先考虑窗墙比、传热系数,同时在确定当地太阳得热系数时应兼顾窗墙比和建筑层数,以满足更高的节能标准。

建筑多孔围护结构热湿耦合迁移研究进展

建筑多孔围护结构的热湿耦合迁移会严重影响建筑室内环境、建筑能耗以及建筑结构,而建筑热桥往往是发生湿迁移和湿积累最严重的部位。与建筑主墙体相比,热桥受多维效应的影响,热湿耦合迁移更加复杂。为探究建筑中不同部位的热湿耦合迁移,从而精准计算建筑热损失,首先分别从一维平壁墙体和多维热桥两个角度阐述了多孔围护结构热湿耦合迁移的研究进展,然后分析了多孔围护结构热湿耦合迁移对建筑的作用。多孔围护结构尤其是其中的热桥等复杂建筑节点处的热湿耦合迁移对建筑室内环境、建筑能耗及建筑结构有着重要影响,热湿耦合迁移模型、热湿耦合迁移实验等相关研究也亟待深入开展。

A Comparative Study of the Thermal Performance of Plastic Bottle Wall against Traditional Composite Brick Wall Typologies

According to the container recycling institute,nearly a million plastic beverage bottles are sold every minute around the world.Plastic bottles are considered as an urban junk,however,it has shape characteristics which make them usable in construction in lieu of conventional bricks.This research promotes the use of recycled plastic bottles as eco-bricks by substituting it with the typical construction bricks.It evaluates the thermal performance of sand filled plastic bottle-walls in a comparative analysis with traditional composite brick walls.The thermal performance of the plastic bottle walls was evaluated through COMSOL®Multi-physics and the results are noted.

轻型木结构剪力墙保温性能测试与分析

以国内首栋六层梁柱框架-轻型木结构剪力墙——山东鼎驰木业有限公司研发大楼为研究对象,对其一楼质检部墙体A与二楼仓库墙体B的传热系数进行测定分析。热流计分别呈横向与纵向布置,分别采取空调加热和电暖器加热,测试不同部位墙体的保温隔热性能;参照标准GB 50176—2016计算墙体理论传热系数;采用Abaqus软件对墙体传热系数进行模拟并对墙体内部温度与热流密度分布展开分析。研究结果表明:墙体A(横向)与墙体A(纵向)的平均传热系数分别为0.463、0.465 W/(m^(2)·K),墙体B的平均传热系数为0.374 W/(m^(2)·K),均达到了寒冷地区甲类公共建筑外墙标准;各测点传热系数实测值有一定差异,墙体保温性能不均匀,受施工条件与结构形式影响较大;墙体传热系数的理论结果与数值模拟结果分别为0.238 W/(m^(2)·K)和0.233 W/(m^(2)·K);保温层墙骨柱区域热流密度相比于保温棉区域显著提高,墙骨柱处易形成热桥,导致热流量和传热系数大幅上升,保温隔热性能下降。

地下建筑热湿行为模拟研究:模型、计算工具和边界条件

多孔建筑材料热湿耦合模拟已被广泛应用于建筑模拟。地下建筑随着城市土地的稀缺而愈发受到关注的同时,相关的湿热研究却很少被关注,主要是因为地下建筑内部复杂的湿热负荷和模拟中的大面积土壤。为准确预测和优化地下建筑的湿热性能,指导地下建筑相关的湿热模拟,通过范围界定论文综述的方法,介绍了热湿传递的理论方法,并从数值模型、计算工具以及边界条件的角度,总结了现阶段地下建筑热湿模拟中的成果和不足。结果表明:地下建筑热湿模拟的挑战在于土壤成分和水分的不确定性、土壤表面的雨水沉淀和水分迁移以及较大土壤域带来的巨大计算成本。两步法虽然简化了模拟,但不足以用于热湿模拟,需要确定一种公认的程序、方法来直接确定地下建筑外边界条件以降低模拟复杂性。

夏热冬冷地区公共建筑绿色建筑围护结构增量分析研究——以苏南地区建筑为例

新建建筑申报一二三星级绿色建筑,围护结构热工性能要求提高,主要降低外墙、屋面及外窗的传热系数及外窗的太阳能得热系数,这需要增加围护结构保温材料厚度。本文收集夏热冬冷地区申报绿色建筑项目案例,通过对部分公共建筑项目案例建模分析,计算不同星级建筑围护结构保温材料的厚度,并与国家建筑节能设计标准要求进行对比,分析不同星级绿色建筑保温材料的厚度变化,对该地区的新建建筑确定绿色建筑增量成本提供一定的依据。

建筑外墙延迟衰减特性的组合优化方法

研究建筑外墙不同组合延迟衰减特性对建筑峰值传热的影响规律,对降低峰值传热负荷,减少空调系统配置容量具有重要意义.针对某案例建筑,采用EnergyPlus与正交试验设计方法,研究多类型建筑外墙组合延迟衰减特性与峰值传热冷负荷的变化规律.结果表明:各墙体组合对外扰具有不同的延迟衰减特性,导致峰值冷负荷大小存在显著差异,差异度最大为11.8%.基于不同类型建筑外墙传热峰值出现时刻不同,叠加后可降低总传热量峰值的特性,提出一种外墙峰值传热优化组合方法.在各朝向墙体内表面温度关系式中引入错峰指标PSI,用于调节墙体组合的延迟时间,以该指标为设计变量,墙体总传热量峰值为目标函数,通过优化求解得到各朝向墙体的最佳延迟时间,进而求出优化墙体组合.采用该方法对案例建筑进行计算,结果显示:对建筑外墙进行优化组合后,其总传热量峰值降低了19.1%.

围护结构传热系数检测方法的实验研究

围护结构传热系数是准确计算建筑能耗的关键参数,其检测是建筑节能工程验收必不可少的检测项目之一。现行有效的标准推荐采用热流计法对围护结构传热系数进行测量,但对热流计贴敷方式未做出明确规定。该文说明了准确测量围护结构传热系数的意义,介绍了测量方法和关键技术要点、测试仪器原理。对热流传感器外贴敷铝箔胶带的安装方式和未贴敷铝箔胶带的安装方式进行实验比对,所测得数据显示贴敷铝箔胶带会导致检测结果偏小,测得热流密度的最大相对误差可达到-13.39%,传热系数相对误差为-11.01%,该误差会导致后续耗热量、节能量等综合指标的计算的偏差,影响检测结果的准确性。

某办公建筑围护结构节能改造效果分析

针对北京市某办公建筑围护结构节能改造,对建筑围护结构热工缺陷、传热系数、室内温度等热工参数进行测评,并结合实测数据进行模拟计算。结果表明:围护结构节能改造对提高建筑的热舒适性、降低建筑能耗效果显著,尤其可以明显降低冬季热负荷;在围护结构改造措施中建筑外窗和外墙改造的节能效果明显,而屋面改造节能效果较弱。此分析结果可为既有公共建筑围护结构节能改造提供技术参考。