【作者】 郭兴国；

【导师】 陈友明；

【作者基本信息】 湖南大学 ， 供热、供燃气、通风及空调工程， 2010， 博士

【摘要】 在我国南方地区,气候变化剧烈并且长期处于高温高湿气候条件下,墙体的热湿迁移对建筑围护结构的热工性能、建筑能耗和室内环境有着十分重要的影响。因此,本文以多孔介质传热传质学为理论基础、以建筑围护结构内的热湿迁移及湿积累问题为工程背景对南方热湿气候地区多层墙体的热湿耦合迁移特性进行了深入、系统的研究。首先,对热湿气候地区多层墙体的传热传质规律进行了详细分析和讨论。在Budaiwi模型的基础上,通过考虑相变以及墙体内部液态水传递建立了多层墙体热湿耦合传递模型。将墙体与周围介质的质量、能量传递过程作为问题的边界条件处理,将墙体内部水分的蒸发冷凝换热作为能量守恒的一部分。该模型以空气含湿率和温度为驱动势,避免了多层材料交界处或材料与空气边界处的不连续现象,从而可将材料内部的热湿迁移过程与材料表面吸放湿过程联系起来,使分析过程变得简便。利用有限容积法对模型进行离散,为了确保数值稳定性,采用隐式格式。用系数更新法将非线性离散方程组化为线性方程组,然后利用Gauss-Jordan消元法对线性方程组进行求解。开发了分析计算程序。对数值模型的精度进行了分析。为了验证模型的正确性,将模型预测结果与实验测试数据进行了对比,二者吻合良好。室外侧分界面处的空气相对湿度的平均偏差为4.2%,平均温度偏差为1.1K,室内侧分界面处的空气相对湿度的平均误差为5.7%,平均温度偏差为0.95K。建立了多层墙体热湿耦合传递的实验测试方法。以水泥砂浆-砖-水泥抹灰墙体为代表,在实际气候条件下对长沙地区1月份和7月份空调房间外墙体内的温湿度分布进行了测试。对该红砖墙体而言,实验测试结果表明：(1)无论是在夏季还是在冬季,该红砖墙体内的温、湿度变化都存在着很强的耦合作用,并且温度对湿度的影响尤为显著。(2)无论是在夏季还是在冬季,水泥砂浆与红砖界面处的温度、湿度都严重受到室外温、湿度变化的影响,室内环境的变化对其影响比较小,红砖与水泥抹灰界面处的温度、湿度主要受室内温、湿度的影响,变化较小。(3)在夏季和冬季进行空气调节时,不论阴雨天还是晴天,水泥砂浆与红砖界面处的相对湿度均有可能达到饱和状态,并有相当长的时间该位置的相对湿度高于80%。(4)在夏季时,内表面贴有发泡塑料壁纸的墙体2内各界面处的温、湿度普遍比没有贴壁纸的墙体1内相应界面处的要高；在冬季时,两种墙体内各界面处的温度基本相同,但没贴壁纸的墙体1内各界面处的湿度比贴壁纸的墙体2中的湿度要略高。(5)无论是在夏季还是在冬季,阴雨天气候对墙体内的含湿量影响都很大,会造成水泥砂浆与红砖界面处的相对湿度长期接近饱和状态,并且存在水分凝结现象。(6)无论是在夏季还是在冬季,太阳辐射强度对墙体内的温、湿度变化都存在着很大的影响,且明显影响着墙体内温湿度的分布规律。以所建立的热湿耦合传递模型为主模型,以忽略太阳辐射影响的热湿传递模型为子模型1,以纯导热模型为子模型2。将主模型的计算结果分别与子模型1和子模型2的计算结果进行比较,得出太阳辐射和湿传递对墙体热湿性能的影响。根据Motakef和EI-Masri的热湿同时传递理论,将水蒸气冷凝看成是湿源、热源、蒸汽汇,建立了冷凝区域内的热湿同时传递方程。给出了稳态阶段和瞬态阶段湿区域位置的确定方法。通过分析解得出了墙体内的冷凝率分布函数、液态含湿量分布函数以及达到临界含湿量所需的时间。根据湿分布情况得出了冷凝对材料导热系数的影响。利用自编程序对南方地区几种典型墙体的热湿性能进行了详细分析。最后根据室内产湿率、换气效率及室内外温度条件得出了基于预防霉菌生长的墙体的最小热阻的确定方法。更多还原

【Abstract】 In hot and humid climate of south China, the heat and moisture transfer through wall has an important impact on the hygrothermal performance of building envelope, energy consumption and indoor environment. Therefore, in this dissertation, based on the heat and moisture transfer through porous media, the characteristics of heat and moisture transfer through multilayer wall subjected to hot humid climate of south China are systematically studied by taking the moisture migration and accumulation in building enclosed structures as an engineering background.First, the detailed analysis and discussion on the laws of heat and moisture transfer through multilayer wall was conducted. Based on the Budaiwi model, coupled heat and moisture transfer model was established by considering phase change and liquid tranfer within wall. The mass and energy exchange between wall and air was taken as boundary conditions in this model and the heat produced by vapour phase change occurring within wall was taken as a part of energy balance. The discontinuity between material and air or the interface between different materials was avoided by using air humidity ratio and temperature as driving potentials. Therefore, the heat and moisture transfer process within materials can be linked with desorption/adsorption process at the material surface which make the analysis process easier.To ensure the numerical stability, the governing equations were discreted by finite volume method with implicit forward differences for time. The linear equations were obtained from the non-linear equations using coefficients updating method. The solution of linear equations was obtained by Gauss-Jordan elimination technique. A compution program was developed. The accuracy of the numerical model was analyzed. To evaluate the correctness of the model, the prediction of the model was compared with the experimental test data. The prediction results have good agreement with the experimental results. For the interface close to outdoor side, the average deviation of temperature and relative humidity is 1.1K and 4.2%, respectively. For the interface close to indoor side, the average deviation of temperature is 0.95K and the average deviation of relative humidity is 5.7%.An experimental setup was built to test the coupled heat and moisture transfer in a multilayer construction. Taken cement mortar-red brick-cement plaster multilayer wall under natural climatic boundary conditions as an example, the temperature and relative humidity was measured in the external walls of an air-conditioned room in Changsha during January and July. The experimental results showed that:(1) Whatever in summer or winter, the temperature and humidity ratio within the wall was coupled strong and the effect of temperature on humidity ratio was more important.(2) Whatever in summer or winter, the temperature and humidity at the interface between the cement mortar and red brick were seriously affected by the variation of outdoor temperature and humidity. The temperature and humidity at the interface between the red brick and cement plaster had small variations; they were affected by the variation of indoor temperature and humidity.(3) The relative humidity at the interface between cement mortar and red brick was likely to reach saturation in summer and winter during the period of air-conditioning. In addition, the relative humidity was kept at higher than 80% for a long-term.(4) In summer, the temperature and humidity at the interfaces of the wall with foamed plastic wallpaper were generally higher than those of the wall without treatment. In winter, the temperature at the interfaces of two walls was basically the same, but humidity at the interfaces of the wall without treatment were slightly higher than that of the wall with foamed plastic wallpaper.(5) Whatever in summer or winter, rainy day climate has a great influence on the moisture content in the wall, which can cause to relative humidity at the interface between the cement mortar and red brick close to saturation for a long-term.(6) Whatever in summer or winter, solar radiation intensity has a great impact on the distribution and variation of temperature and humidity inside the wall.Regarded the hygrothermal model established in this dissertation as main model, the hygrothermal model neglecting solar radiation as sub-model 1 and the well-kn(?)n conduction equation as sub-model 2. Results calculated by main model are compared with the results calculated by the sub-model 1 and sub-model 2. Through these comparisons the effects of solar radiation and moisture transfer on hygrothermal performance of multilayer wall are obtained.According to the work of Motakef and EI-Masri, taken the vapour condensation as a vapour sink, water source and heat source, coupled heat and moisture equations for wet zone were established. The determination of wet zone for steady stage and unsteady stage are provided. Closed-form analytical expressions for the condensation rate, moisture content and the time at which critical moisture content value is reached are obtained. The effect of condensation on material thermal conductivity is obtained according to the moisture content distribution.Detailed analysis on hygrothermal performance of several typical walls of south China is conducted using the codes developed in this dissertation. Finally, the determination method of minimum thermal resistance to prevent mould growth is proposed according to internal moisture production rate, air change rate, indoor and outdoor temperature.更多还原