新建建筑不同设置围护结构的热质耦合传递对建筑负荷的影响Ⅱ:冬季湿负荷

传统建筑室内湿负荷的计算大多不考虑围护结构内表面的散湿量,而围护结构内表面的散湿量尤其是新建节能建筑对室内湿负荷的影响是很大的。以哈尔滨地区为例,分析了严寒地区典型新建建筑不同设置的多层围护结构在最初四年内热质耦合传递对模拟房间湿负荷的影响,并与文献[5]的模拟结果进行对比。分析结果表明：新建建筑围护结构内表面粘贴墙纸或降低围护结构主体砌块的初始含湿量能够降低模拟房间冬季湿负荷;而保温层内侧隔汽层以及围护结构外表面釉面砖的使用都会增加新建建筑的模拟房间冬季湿负荷,但若延后釉面砖的粘贴时间会有所好转。     

新建建筑围护结构的热质耦合传递对建筑负荷的影响Ⅰ：冬季热负荷

对于节能建筑,围护结构保温性能优劣是影响其能耗的重要标准.以哈尔滨地区为例,通过对新建建筑围护结构热质耦合传递的模拟结果,对比分析了严寒地区典型新建建筑不同设置的多层围护结构在最初四年内热质耦合传递对围护结构墙体热负荷的影响.分析结果表明:围护结构保温层内表面安装隔汽层能有效缓解保温层受潮,对降低能耗较为有利,围护结构外表面粘贴釉面砖时对能耗影响最大,但若降低保温层初始含湿量会降低其影响.     

太阳辐射对含湿墙体的热作用──一种新的空调负荷计算及预报方法

讨论了一种新的计算含湿建筑墙体空调负荷的数学模型及数值计算方法，并对新建建筑墙体在若干年内的空调负荷实现预报。     

新建建筑围护结构的传热系数变化研究

对严寒地区新建建筑围护结构的干燥过程进行了模拟,建立了不同干燥时期的热质耦合传递质能平衡方程,确立了围护结构各层多孔介质材料导热系数随含湿量和结冰量的变化关系,对围护结构传热系数的变化情况进行了模拟,分析了新建建筑传热系数随着围护结构不断干燥的逐年变化规律。模拟结果表明:在严寒地区,新建建筑围护结构冬季的传热系数由于内部含湿量结冰要高于夏季围护结构传热系数,但围护结构冬季传热系数逐年下降,尤其前三年下降较明显。     

湿分对加气混凝土砌块导热系数影响实验研究

加气混凝土砌块广泛用于建筑中,热工性能分析中若未充分考虑湿分的影响会导致大的误差。实验测试了潮湿环境下加气混凝土砌块平均含湿量与导热系数的变化,分析了湿分对导热系数的影响,拟合得到加气混凝土砌块导热系数与平均含湿量之间的关系。结果表明:在潮湿环境下,湿分会快速进入加气混凝土中,含湿量的增加会导致加气混凝土的导热系数增加。因而,应充分考虑潮湿环境对加气混凝土建筑热工性能的影响。     

多层多孔介质层间界面处的热质耦合传递

为解决多层多孔介质层间界面处含湿量不连续而使含湿量梯度不能直接作为质传递驱动势的问题,该文在仍然以含湿量梯度为质驱动势的条件下,对界面处的质量和能量守恒方程进行适当改进,使对多层多孔介质热质耦合传递的模拟结果更符合实际,通过对已发表文献的实验结果进行验证,利用验证改进后的模拟方法对新建建筑多层多孔介质围护结构进行模拟,并与以界面处的平均体积含湿量梯度作为质驱动势对模拟结果进行对比。对比结果发现:利用改进后的模拟方法模拟的围护结构干燥速度小于后者的模拟结果,模拟结果也更接近实际情况。     

湿燃气透平叶片热流固耦合换热特性的数值研究

为评估湿空气透平循环中湿燃气对透平叶片燃气侧换热特性的影响,以及湿空气对透平叶片冷却效果的影响,以C3X叶片为例,采用热流固耦合的数值计算方法,研究了湿燃气含湿量对透平叶片表面温度和传热系数的影响,对比分析了干空气与湿空气冷却效果的差异.同时在研究范围内给出了透平叶片燃气侧传热系数的无量纲关系式,为湿化燃气轮机透平叶片的优化和冷却结构设计提供参考.结果 表明:湿燃气含湿量对透平叶片燃气侧的流动性能基本无影响;当湿燃气含湿量从0 g/kg增加到150 g/kg,主流进口温度为1473 K时,透平叶片表面平均传热系数增加10％,且增加幅度随着主流进口温度的升高而增大,叶片表面最高温度平均提高10 K;与干空气相比,湿空气作为冷却工质时的叶片表面温度更低,冷却效率更高,且冷却效率随着湿空气合湿量的增加而提高.     

含湿多孔介质内热量迁移的研究

文中分析了未饱和含湿多孔介质内热湿耦合作用过程的热迁移机量，提出了热量迁移数学模型，讨论了不同边界条件对多孔介质内温度分布的影响状况。     

围护结构热质耦合传递实验研究

对单层围护结构热质耦合传递过程进行了实验研究。在建立围护结构墙体时,预留一块围护结构用炉渣混凝土砌块测量其孔隙率,初始体积含湿量,干、湿状态的导热系数以及完全干燥状态的密度,并计算砌块固体骨架的导热系数。实验测量321d,该文对实验结果进行了分析,分析结果表明:随着边界条件的变化,围护结构表面及内部温度能够很快达到平衡;但由于湿扩散速度比热传递速度慢得多,因此只有围护结构内外表面的相对湿度受边界条件影响,围护结构中间的相对湿度稳定并持续很高。     

建筑墙体热、湿及空气耦合传递

为了研究建筑墙体的热质耦合传递规律，该文考虑了太阳辐射的影响，建立了在第三类边界条件下建筑墙体非稳态热、湿及空气渗透耦合传递的物理及数学模型，开发了相应的数值模拟计算软件。给出了墙体热、湿及空气耦合传递时各部位模拟计算温度随时间的变化曲线及不同使用年限湿容量沿墙体厚度的分布规律，并将墙体的模拟计算结果与现场实测热流及温度进行了对比分析。     

Measuring and modeling vapor boundary layer growth during transient diffusion heat and moisture transfer in cellulose insulation

In this paper, an experimental test facility that permits continuous measurements of transient heat and moisture transfer in porous media is applied to study the vapor boundary layer in cellulose insulation. The experiment measures the relative humidity, temperature and moisture accumulation within the cellulose specimen with a fully developed flow of air at a controlled temperature and humidity provided above the surface. These experimental results are used to verify a mathematical model, which is used to develop an expression for moisture diffusivity (α_m) that is analogous to thermal diffusivity, and takes into consideration moisture storage. The moisture diffusivity is used to calculate the vapor density in the boundary layer and the size of vapor boundary layer in cellulose insulation. It is found that the moisture storage effect has a very significant effect on the vapor boundary layer and cannot be ignored. For cellulose insulation, the size of the vapor boundary layer may be over predicted by a factor of ten when moisture storage is neglected.     

Heat and moisture transfer in fibrous thermal insulation with tight boundaries and a dynamical boundary temperature

Prefabricated, lightweight building elements are widely used in the building construction sector. Such elements consist of fibrous thermal insulation encapsulated between two metal sheets. Under various circumstances, moisture can appear in the insulation matrix. Since the temperature of the boundary metal sheets changes dynamically with meteorological conditions, heat and mass transfer between boundaries appear in this case. This paper presents a transient model of the heat and mass transfer, including the sorption and condensation processes. A numerical model considers the dynamical changing of the boundary temperatures. A parametric study considering different amplitudes of temperature change, different moisture masses and different thicknesses of the insulation matrix was made. It was found that a relatively small mass of water in the insulation matrix can result in a significantly increased average heat flux during a periodic cycle. The numerical code was verified with experiments, which showed good agreement with the numerics.     

建筑外墙外保温中锚固件的检测

锚固件在建筑外墙外保温中起到增强保温层和基层墙体连接的作用。依据建筑外保温锚固件检测标准,通过现场试验对其在不同条件下的实际抗拉承载力进行研究,阐述了外保温锚固件检测抗拉承载力的影响因素。     

Experimental study on the impact of mass moisture content on the evaporative cooling effect of porous face brick

Porous face bricks on the outside of a building wall exhibit evaporative cooling after absorbing water. Thus, these bricks are promising for use as a passive energy-saving building technology. Artificial watering is an effective method to ensure a sufficient water supply for effective evaporative cooling. However, improper watering measures may result in the waste of water resources while failing to achieve the evaporative cooling effect. In this paper, studies were conducted on a composite wall composed of a facing layer and a base layer as follows. (1) The mass moisture content variations in the porous face brick with respect to soaking time were measured, and the feasibility of using this type of face brick as an evaporative cooling carrier was investigated. (2) The relationship between mass moisture content and the evaporation capacity of the porous face brick was determined under stable conditions. A critical mass moisture content for the porous face brick was determined through analysis of the measurement data. (3) A field measurement was performed to verify the feasibility of using the critical mass moisture content as a criterion for watering. The results indicate that the temperature and heat flows at the inner and outer surfaces of the composite wall were reduced significantly. However, when the mass moisture content exceeded the critical mass moisture content, the evaporative cooling capability tended to stabilize with further watering. Therefore, the critical mass moisture content of the porous face brick can be used as a criterion for watering to conserve water while facilitating the evaporative cooling effect.     

The application of dynamic insulation in buildings

Dynamic insulation, a form of ‘Breathing Wall’ construction which allows the movement of air and moisture through the external walls of a building, was seen as one possible method for reducing building envelope heat losses and achieving high indoor air quality. A research investigation was conducted to provide a firm scientific understanding of dynamic insulation. An important outcome of the work will be the development of building envelope designs which effectively and economically employ dynamic insulation in cold climates. This paper presents some general conclusions, confirming that the energy saving produced by dynamic insulation alone is small relative to that obtained in conjunction with conventional air heat recovery methods.     

绿色建筑能耗影响因素研究

经济迅猛发展和城市化进程的加快,推动了建筑业的繁荣,但同时建筑能耗问题也日益严重,在能源稀缺供不应求的背景下,建筑业节能降耗迫在眉睫。文章从降低绿色建筑能耗角度出发,从建筑朝向和形状、窗户隔热和遮阳、墙体围护结构、人的行为、气候因素、建筑节能政策等6个方面对绿色建筑的能耗进行了研究,并采用ISM法(解释结构模型法)分析了这6个因素对建筑能耗的影响程度。研究表明,气候因素对绿色建筑能耗影响最大,其次是建筑节能政策、人的行为。最后,根据研究结果提出了相应的节能对策。     

XLPE表面缺陷对电场及击穿电压的影响

电缆中间接头施工过程中易造成XLPE表面划伤、附着污染颗粒和表面受潮三种缺陷,为评估缺陷对接头运行性能的影响,建立了电缆中间接头XLPE绝缘片状模型,分析了不同缺陷下电场的变化,探究了不同缺陷对电场及击穿电压的影响程度。结果表明,XLPE在划伤时划痕处的电场产生严重畸变,为非划痕处的1.6倍;受潮时XLPE表面附着污染水中导电杂质越多,污染水的电导率越高,从而使其导电性能增强,电场强度变大,是同界面处非受潮部分的1.22~1.40倍;XLPE表面附着污染颗粒时,颗粒与其交界面处电场发生较严重畸变,是同界面无缺陷时的1.50倍左右,划痕对XLPE绝缘的电场影响最严重。通过试验结果显示正常无缺陷时的击穿电压为129.6kV,划伤缺陷的击穿电压为59.1kV,受潮缺陷的击穿电压为69.7kV,杂质缺陷的击穿电压为59.2kV,划痕对XLPE绝缘的击穿电压影响最严重。研究成果为探究不同缺陷对电缆中间接头XLPE绝缘性能的影响提供了重要依据。     

An experimental data set for benchmarking 1-D, transient heat and moisture transfer models of hygroscopic building materials. Part II: Experimental, numerical and analytical data

This paper presents the experimental results on spruce plywood and cellulose insulation using the transient moisture transfer (TMT) facility presented in Part I [P. Talukdar, S.O. Olutmayin, O.F. Osanyintola, C.J. Simonson, An experimental data set for benchmarking 1-D, transient heat and moisture transfer models of hygroscopic building materials-Part-I: experimental facility and property data, Int. J. Heat Mass Transfer, in press, doi:10.1016/j.ijheatmasstransfer.2007.03.026] of this paper. The temperature, relative humidity and moisture accumulation distributions within both materials are presented following different and repeated step changes in air humidity and different airflow Reynolds numbers above the materials. The experimental data are compared with numerical data, numerical sensitivity studies and analytical solutions to increase the confidence in the experimental data set.     

Modeling heat and moisture transfer through fibrous insulation with phase change and mobile condensates

This paper reports on a transient model of coupled heat and moisture transfer through fibrous insulation, which for the first time takes into account of evaporation and mobile condensates. The model successfully explained the experimental observations of Farnworth [Tex. Res. J. 56 (1986) 653], and the numerical results of the model were found to be in good agreement with the experimental results of a drying test. Based on this model, numerical simulation was carried out to better understand the effect of various material and environmental parameters on the heat and moisture transfer. It was found that the initial water content and thickness of the fibrous insulation together with the environmental temperature are the three most important factors influencing the heat flux.