多孔建材VOC多尺度传质机理及散发特性研究

发布时间：2018-03-12 08:30

本文选题：多孔建材　切入点：挥发性有机化合物(VOC)　出处：《西安建筑科技大学》2017年博士论文　论文类型：学位论文

【摘要】：挥发性有机化合物(Volatile Organic Compounds,VOCs)作为室内空气污染的主要来源,广泛存在于室内装饰、装修建材内部。近年来建筑节能目标的快速推进使得建筑物趋于高度围合密闭,促使VOC在室内空气中积聚,对室内人群的身体健康及工作效率产生了极大的影响。世界卫生组织公布的数据显示每年约有400万人因室内空气污染导致的非传染性疾病而过早死亡。现有对建材VOC散发特性的研究多停滞在唯象表观层面,而掌握多孔结构复杂的孔隙特征及差异化传质机理是确定建材VOC散发特性的基础,也是指导VOC控制策略的前提。鉴于此背景,本文采用理论分析、实验测试和数值计算相结合的研究方法探讨了多孔建材VOC的多尺度传质机理及散发特性,具体研究内容及学术成果如下:突破传统连续介质模型维度空间的藩篱,将分形几何理论应用于多孔建材VOC有效扩散系数预测,基于建材内传质孔道的变径特征,在分形毛细管束模型的基础上发展了有效扩散系数的多级串联宏观分形毛细管束模型。该模型通过对多孔建材孔隙结构进行剖析,探究宏、介观孔的分布特征及传质网络连接模式,阐明了宏观孔串联传质通道的分形幂规律分布及介观孔的辅助传质特性。通过压汞实验测量的建材结构参数可实现对有效扩散系数的直接预测,结合环境舱的建材VOC散发实验对该理论模型的准确性予以验证,相比经典扩散系数模型显著提高了预测精度。基于吸附势理论诠释了多孔介质的非均匀活性中心对VOC分子吸附特性的影响,以Dubinin-Radushkevich吸附等温式和Freundlich吸附等温式推导了多孔建材分离系数的双尺度计算模型,分别适用于微观孔及宏、介观孔的分离系数预测。相比基于Langmuir单分子层吸附理论的分离系数模型,双尺度计算模型综合考虑了孔隙结构差异对分离系数的影响。为验证模型的准确性,发展了阶跃温度工况下分离系数与初始可散发浓度的连续测量实验方法,通过实验数据的拟合,可将预测结果拓展至同系物间分离系数的确定。此外,以宏、介观尺度分离系数解析式为传递参数,可将前述理论求解的有效扩散系数转换为表观扩散系数,建立表观扩散系数与温度的函数关系,实现多孔介质模型与单相传质模型间的参数转换。系统地剖析了VOC分子多尺度脱附机制,以孔隙结构参数对多孔建材吸附势能差异化分布规律进行准确数学表征,代替以均值或经验公式计算吸附势能,由分子动能概率密度分布与吸附势能分布律之间的非均匀脱附判据推导初始可散发浓度差异化分布解析式。同时,鉴于同系物间化学性质相似的特征,推导了同系物吸附势能表达式,藉此通过少量实验拟合即可实现对建材内多种同系物初始可散发浓度的同时预测。通过对建材VOC散发的敏感性分析,探讨了散发关键参数及其主控因素的影响程度。针对三种VOC散发源头控制方法,即吸附剂的均匀掺混、表面阻隔及基材固定,建立了不同吸附剂添加方式下建材VOC散发关键参数的预测体系,可对建材VOC源头控制效果进行理论分析。结果表明,均匀掺混吸附剂对VOC散发的全局控制效果最好,吸附剂表面阻隔的短期散发抑制效果显著,而基材固定则适用于长期散发过程。通过对VOC源头控制效果的预测可为工程应用遴选适宜的VOC控制策略提供依据。
[Abstract]:Volatile organic compounds (Volatile Organic, Compounds, VOCs) as the main source of indoor air pollution, widely exists in the interior decoration, interior decoration materials. In recent years, the rapid advance of the goal of building energy-saving buildings tend to be highly enclosed sealed, prompting VOC to accumulate in the room air, has a great impact on health and work efficiency indoor population. WHO released data show that about 4 million people due to indoor air pollution and non communicable diseases and premature death each year. The existing research on VOC emission characteristics of building materials more apparent stagnation in the phenomenological level, grasp the characteristics and differences of the pore complex porous structures of the mass transfer mechanism is the basis for determining the VOC emission characteristics of building materials the VOC control strategy and guide the premise. In view of this background, this paper based on theoretical analysis, experimental testing and numerical combination Research methods and emission characteristics of multi-scale mass transfer mechanism of porous building materials VOC, the research contents and academic achievements are as follows: break through the traditional continuum model dimensional barriers, the theory of fractal geometry is applied to porous materials VOC effective diffusion coefficient prediction, variable characteristics of mass transfer channels based on the development of building materials, the macro fractal series the capillary bundle model of effective diffusion coefficient based on fractal capillary model. The model based on the pore structure of porous building materials to analyze, explore macro distribution and mass transfer network of mesopores connection mode, the auxiliary power law distribution and mass transfer characteristics of fractal mesoscopic hole hole macroscopic mass transfer channel. Through a series of building materials the structure parameters of mercury injection experiment measurement can realize direct prediction of effective diffusion coefficient, combined with environmental class building materials VOC emission experiment of the theory model The accuracy is verified, compared with the classical diffusion coefficient model significantly improves the prediction accuracy. The adsorption potential theory to explain the effect of non-uniform porous media based on the active center of VOC molecular adsorption, Dubinin-Radushkevich isotherm and Freundlich isotherm derived dual scale porous building materials separation coefficient calculation model, which are suitable for micro Jihong hole, prediction of separation coefficient. Compared with mesopores separation coefficient model of Langmuir monolayer adsorption theory based on dual scale calculation model considering the effect of pore structure on the coefficient difference. In order to verify the model, continuous measurement method developed step temperature separation coefficient and initial emittable concentration by fitting the experimental data, the prediction results can be extended to determine the separation coefficient between homologues. In addition, the macro, meso Scale separation factor analytic formula for the transmission parameters, which can convert the effective diffusion coefficient of the theory for the apparent diffusion coefficient, the establishment of form function relationship apparent diffusion coefficient and temperature, the parameters of porous medium model and single phase mass transfer model of the conversion between. Systematic analysis of the multi-scale VOC molecular desorption mechanism, the pore structure the parameters on the adsorption potential of porous building materials poor accurate mathematical characterization of alienation distribution, replaced by the mean or empirical formula to calculate the adsorption potential between molecular kinetic energy probability density distribution and adsorption potential distribution law of non uniform criterion is the initial desorption emittable concentration difference distribution formula. At the same time, in view of characteristics of similar chemical properties between homologues the expression of homologues, adsorption energy, thereby the experimental fitting can be realized by a small amount of building materials in a variety of initial emittable concentration with homologues When forecasting. Through the sensitivity analysis of VOC from building materials, the influence of key parameters distribution and its main controlling factors. According to the three VOC emission source control method, namely mixed adsorbent mixture, surface barrier and the substrate is fixed, establishes a prediction system of different ofadsorbent mode VOC distributed key parameters of building materials the theoretical analysis of building materials, VOC source control effect. The results show that the adsorption effect of uniformly mixing global control agent on VOC from the best adsorbent surface barrier short-term dissemination of inhibition effect is significant, while the substrate is suitable for long-term fixed emission process. By predicting the control effect of VOC source can provide the basis for engineering application VOC the selection of appropriate control strategies.

【学位授予单位】：西安建筑科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X799.1

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