新建建筑围护结构热质传递对室内温湿度环境的影响

新建建筑第1年由于较大的内表面散湿量会影响室内的温湿度水平,严重的会引起围护结构内表面霉菌。为分析新建建筑第1年围护结构的湿传递对室内温湿度环境的影响,本文对哈尔滨地区新建建筑综合热质耦合传递进行了模拟,分别建立了围护结构和室内空气的质能平衡方程,并讨论了夏季不同的室内通风率对围护结构内表面散湿量及室内温湿度的影响,得出了几点重要结论。     

关于气候分区问题的探讨

针对《全国民用建筑工程设计技术措施》暖通空调.动力篇(2009年版)中以"最湿月平均含湿量"作为气候分区判断依据一问题,探讨了含湿量(绝对湿度)和相对湿度概念的不同,指出含湿量是空气加湿或减湿的程度,而相对湿度表示的是空气接近饱和的程度,并进一步分析了湿球温度是空气接近饱和程度的一种度量,是一个独立的空气状态参数。最后笔者通过一些气候分区的举例,进一步说明了湿球温度这一参数在气候分区中的重要性。     

地下洞室多孔墙体热湿传递的数值模拟

提出了一种以温度与相对湿度为驱动势的多孔墙体热湿耦合传递的数学模型,该模型同时考虑了水蒸气与毛细孔内液态水的传递。采用控制容积法将理论方程组离散并编制了计算程序,对深埋地下洞室的墙体进行了热湿传递的数值模拟,得到了墙体温度、相对湿度、热流率、湿流率的变化规律。结果表明,墙体传热过程趋于稳定的时间远小于传湿过程。     

Performance of straw bale wall: A case of study

This research aimed to evaluate a straw bale house located in Bavaria, Germany. An extensive test program was carried out. The experimental work includes compression tests, moisture content, thermal stability of bales and pH. The in situ work includes temperature and relative humidity inside the straw bale wall. The stress-strain behavior of straw bales was investigated including nonlinearity and anisotropy. Thermal stability of bales under constant temperature and relative humidity was studied considering time dependence. The moisture content of straw bale was about 11%, while pH value inside the bale was about 7.29. Moreover, the temperature and the relative humidity between the interior (inside straw bale wall) and the exterior were investigated.     

Ground moisture evaporation in crawl spaces

Air change rate, humidity and temperature were monitored in a naturally and a mechanically ventilated crawl space of the test building, in order to determine the ground moisture evaporation rate and the mass transfer coefficient. The average value of the moisture evaporation with uncovered ground was 3.6–5.7 g/h m², corresponding to the mass transfer coefficient 0.0012–0.0018 m/s. The mass transfer coefficient determined from evaporation showed sufficient agreement with the coefficient calculated from temperature differences. Normally it would have been sufficient to consider natural convection but with high air change, forced convection also had to be taken into account. The higher air change rates increased moisture evaporation, but still brought about lower relative humidity. The lowest relative humidity, 74.5% in summer, achieved with covered ground and air change of 3 ach, indicates that the control of moisture evaporation and thermal behaviour in summer are key elements in the moisture balance.     

温湿度耦合效应下早龄期混凝土的相对湿度场

早龄期混凝土温度和相对湿度的时间空间变化规律是揭示混凝土早期开裂的关键。为此,建立了早龄期混凝土温度湿度耦合作用分析模型,采用无条件稳定向后差分格式,考虑水化作用、自干燥作用、温湿度扩散作用以及温湿度耦合机制,分析早期混凝土相对湿度的时间空间变化规律,定量揭示相对湿度的空间不均匀性,分析了水灰比、环境相对湿度以及表面水分交换系数等对相对湿度及其空间变化规律的影响。与实验结果的对比验证了模型的合理性,结果表明:温湿度扩散作用对相对湿度的影响随距扩散表面距离的增加而减小,水灰比对相对湿度的影响与位置无关,而环境相对湿度和表面水分交换系数主要影响混凝土扩散表面附近的相对湿度场。     

改性材料对生土砌块湿热性能的影响

采用动态试验法和稳态平板法,研究了改性材料对生土砌块吸湿性能和导热系数的影响.结果表明:生土砌块的初始吸湿率、平衡含湿量和60 h吸湿率均随着相对湿度的增加而增加;当相对湿度为40％和60％时,复合改性生土砌块的平衡含湿量均大于石灰改性和水泥改性生土砌块;生土砌块的导热系数随着平衡含湿量的增加而增加;石灰改性和复合改性生土砌块的平衡含湿量、导热系数和干密度随着石灰掺量和纤维掺量的增加而降低;水泥改性生土砌块平衡含湿量随着水泥掺量的增加而降低,与导热系数和干密度的变化趋势相反.     

调湿材料对室内湿环境影响的实验研究

利用3种调湿板材硅藻泥抹面板、纸面石膏板、玻镁板,搭建了模拟用的实验箱,进行了室内湿环境动态变化模拟实验,得到了在不同工况下应用调湿材料模拟小室内相对湿度变化的规律,相对于对比实验箱,结果表明调湿材料有一定的调湿效果,对室内相对湿度的控制能力依次是玻镁板、硅藻泥抹面板、纸面石膏板;分析了散湿源的面积、是否间歇通风换气、间歇湿源、调湿板的面积等实验条件对三种调湿板材的调湿效果影响的程度。     

被动式太阳能集热蓄热墙对室内湿度调节作用的研究

在两间分别采用被动式太阳能集热蓄热墙体和普通保温节能墙体的同实体大的实验房屋中,利用多点温湿度及风速的计算机巡回检测系统,在2004年供暖期对室内外温湿度、风速、太阳辐射照度及墙体内温度等参数进行了实测。结果表明,未采用被动式太阳能集热蓄热墙体的对比房内相对湿度比太阳房高20%左右,并因湿度较高在窗户上出现结露现象。分析了两间实验房屋的热湿传递特性以及对一些物性参数如室内相对湿度、墙体的含湿量、人的舒适性等的影响。     

围护结构热湿耦合传递模型及简便求解方法

为了预测围护结构内的温度和湿度分布,以连续变量,相对湿度和温度为驱动势,考虑热传递与湿传递之间的耦合作用,建立了围护结构热湿耦合传递非稳态模型,并提出了基于多物理场耦合仿真模拟软件COMSOL的热湿耦合传递模型简便求解方法。通过对比新建模型模拟结果与HAMSTAD标准验证实例,验证了模型及求解方法的准确性。     

Simulation efficiency and accuracy of different moisture transfer potentials

Simulation models for moisture transfer in building materials are highly incongruent with respect to the moisture potential used. Often the relatively better numerical efficiency and accuracy of a certain moisture potential is put forward as motivation. Various claims are made in that respect, but factual evidence is typically lacking. This paper aims at providing such support by assessing simulation efficiency and accuracy for capillary pressure, relative humidity and -log(-capillary pressure). To that goal, a suite of benchmark simulations are performed with those three potentials and performances are compared, based on deviations from reference solutions and on numbers of iterations required. The study initially reveals mixed results, showing no consistent advantages for either potential. Further analysis uncovers though that -log(-capillary pressure) suffers from a strongly nonlinear moisture capacity near saturation. This finally results in a decision in favour of capillary pressure and relative humidity, at least for general-purpose moisture transfer simulation.     

Modeling the effect of hygroscopic curtains on relative humidity for spaces air conditioned by DX split air conditioning system

The use of hygroscopic materials for moisture buffering is a passive way to moderate the variation of indoor humidity. Through absorption and desorption, surface materials in the indoor environment, such as curtains, carpets and wall paper, are able to dampen the moisture variations. The moisture buffering capacity of these materials may be used to improve the relative humidity of the indoor environment at reduced energy costs.The objectives of this paper are threefold. The first objective is to derive a theoretical model for the transient moisture transfer between a curtain system and the indoor air for the case where the curtain is placed in front of a wall. The second objective is to conduct experiments inside environmental chambers to validate the theoretical model and to test the ability of curtains to moderate indoor humidity. It is shown that the experimental results for the curtain moisture uptake and the relative humidity inside the chamber compared well with the model simulation results. The third and final objective is to test and evaluate the model under “real environment conditions” for a case study of a hygroscopic cotton curtain, placed in a “typical” office space in the city of Beirut with an area of 25 m² that uses direct expansion (DX) air conditioning system. It is found that hygroscopic curtains maintain humidity of less than 65% during part load operation compared to the upper limit of 70% relative humidity when no curtain is used. On the other hand, it is found that the energy use, as determined by the daily electrical power consumption of the DX system, is almost the same for the two cases, (with and without a curtain), where approximately 20 kWh of energy input is required 13 kWh of sensible energy and 7 kWh of latent energy.     

An experimental set-up for real-time continuous moisture measurements of plywood exposed to outdoor climate

Plywood used in exterior conditions is prone to water uptake and release. The influence of moisture on the strength properties and the decay risk is substantial. Therefore it is crucial to gather knowledge on the moisture behaviour of plywood in service, especially considering the fact that the intrinsic durability of the wood species used, is not exclusively determining outdoor performance. An automatic measurement set-up is proposed. The concept relies on a logger system recording the weight of plywood samples mounted on calibrated load cells. Mass changes are attributed to changes in moisture content induced by monitored environmental conditions such as solar irradiation, wind, rain and relative humidity. Pre- and post-processing of 10 plywood types is elaborated on. Logically, the length of a rain event has an influence on the moisture content of plywood. Differences in moisture dynamics of different plywood types are attributed to veneer thickness, glue type and wood species and their susceptibility to weathering. Further straightforward correlation was found between plywood moisture content, temperature and relative humidity. Time of wetness calculation based on these data illustrates the moisture dynamics of plywood and is a potential basis for service life prediction of plywood.     

CFD模拟在某游泳馆通风空调设计中的应用

在杭州某游泳馆通风空调设计中，为了考察围护结构内表面的结露情况，利用简化的模型进行了CFD数值模拟。本文介绍了这次数值模拟过程，并根据模拟结果分析比较了设计相对湿度不同的两个方案，模拟结果显示，设计相对湿度较小的方案比较经济。本文的模拟结果也可为类似工程的空调设计方案选择提供一定的参考。     

Increasing the indoor humidity levels in buildings with ventilation systems: Simulation aided design in case of passive houses

In modern societies, people spend about 90 percent of their time inside buildings. The challenge of building physics is to ensure that buildings are planned, constructed and built to provide a comfortable and healthy working and living environment. As construction style has changed during recent years, the planning phase has to be much more precise and the need of simulation programs that respond to every little change arises. An increasing problem in Austria is the indoor humidity. In the field of renovated buildings with airtight new building envelopes, mould growth due to high indoor relative humidity (RH) is a persistent problem. On the other hand, in recently realized Austrian passive houses with an air treatment system, the low humidity level of the indoor air is a problem with which scientists have been struggling for some time. It has been observed in numerous measurements and it is also easily computationally detectable that in winter period the indoor relative humidity level often drops below 30% RH. Low and high relative humidity levels have negative effects on the comfort feeling and health of the occupants of the dwelling and should therefore be avoided. However, it is expensive to increase or decrease the humidity in houses mechanically. Therefore, the existing room moisture should be used sensibly in buildings with a ventilation system. In buildings with a high indoor humidity it is necessary to adjust the ventilation depended on moisture production. This paper focuses on low indoor humidity and presents some different methods by which the indoor relative humidity can be regulated. The effects of adapting parameters such as ventilation rate and buffering material in the dwelling were clearly reflected in the measured temperature and relative humidity. “BuildOpt_VIE” software developed at the Vienna University of Technology was used for the dynamic building simulation in this study.     

夏热冬冷地区典型外保温系统的湿气迁移研究

采用墙体保温系统耐候性测试及湿气迁移动态监测平台研究了蒸压加气混凝土砌体的湿气迁移过程,并通过模拟的方法分析了蒸压加气混凝土为主墙体的外保温系统在夏热冬冷地区的湿气迁移特性。结果表明:蒸压加气混凝土砌块的平衡吸湿率随相对湿度的增大逐渐增大。蒸压加气混凝土砌体具有良好的传湿性能,在约14 d时湿气迁移基本稳定。在传湿模拟中,蒸压加气混凝土墙体外保温系统不会出现冷凝,而在相对湿度比较高的部位可能因毛细凝结而出现液态水。为避免这一问题,提出了采用蒸压加气混凝土作为主墙体的外保温系统在特殊部位的水蒸气传输控制技术,有利于提升系统的功能性及耐久性。     

多层墙体热湿耦合传递模型及验证

从非平衡热力学角度论证了多层墙体热湿耦合过程采用水蒸气分压力和温度作为驱动势的合理性。由于水蒸气分压力是含湿量和温度的函数,利用全微分思想,建立了多层墙体热湿耦合传递模型,该方法可避免Budaiwi方法在热湿耦合模型建立过程中采用的空气含湿量与相对湿度间的近似表达式,而且简化了方程系数,便于方程的求解。通过对多层墙体求解结果的对比,验证了该模型的有效性。     

Experimentelle Bestimmung der hygrischen Sorptionsisotherme und des Feuchtetransportes unter instationären Bedingungen

Experimental determination of the hygroscopie sorption isotherm and the moisture conductvity under transient conditions. By means of the proposed Instantaneous Profile Method (IPM) the relative humidity or the capillary pressure as well as the volumetric water content at specific locations inside a porous medium can be determined. The measurements are carried out under transient conditions and continuously in time. Thus, the IPM allows dynamic measurements of the hygroscopic sorption isotherm and the hygroscopic moisture conductivity. In addition, the moisture conductivity can be obtained via calculation of the moisture flow distribution from the temporal change of moisture contents in the compartments of the sample. The application of non‐constant boundary conditions in the IPM allows investigation of the hygrodynamic behaviour of porous materials. In the presented study, the time and process dependent moisture retention characteristic and moisture conductivity are determined. The adsorption and successive desorption experiments presented here have been performed on the capillary active insulation material Calcium Silicate. The results show a hysteretic behaviour with a pregnant influence of the process dynamics. At locations with a rapid moisture increase, the moisture retention characteristic is shifted up in comparison to regions with slow moisture change. The moisture conductivity as function of relative humidity shows a remarkable hysteresis. However, the moisture conductivity in relation to the water content turned out to be non‐hysteretic.     

Assessing the environmental performance of stabilised rammed earth walls using a climatic simulation chamber

The SHU climatic simulation chamber is a novel piece of apparatus that allows testing of full-sized walls with realistic inner and outer wall climatic conditions. Four SRE test walls were successfully constructed and tested over four separate regimes to measure physical properties such as pressure-driven moisture ingress, rate of moisture penetration, and internal/interstitial condensation. The walls far exceeded a series of cyclic pressure-driven rainfall penetration tests based on BS 4315-2. After 5 days of exposure to static pressure-driven moisture ingress there was no evidence of moisture penetration or erosion. The embedded sensor array detected no significant increase in the relative humidity or liquid moisture content inside the test walls, throughout a range of temperature differentials with high levels of humidity, indicating a negligible risk of internal or interstitial condensation.     

具有调湿功能的内墙乳胶漆

研制一种能调整室内湿度的乳胶漆,通过高吸水聚合物、硅藻土、凹凸棒粉等材料的协同作用,使漆膜能吸收和释放水蒸气,调整室内空气的相对湿度,使人感觉更舒适。