相变围护结构热特性与改进-兼容型相变传热数学模型研究

The use of the building envelope compositing phase change material (PCM) is one of the approaches which are effective and subjected to be studied for reducing energy consumption and improving the indoor thermal comfort degree. In this research project, aiming at the unsteady and nonlinear heat transfer process of the wall compositing PCM, the enthalpy model and effective heat capacity model are used, and the influencing mechanism on the computational accuracy of the traditional mathematical models is revealed, which is from the aspects of the widths and overlap degree of PCM’s melting/freezing temperature ranges, the nonlinear heat absorption and release processes, and the liquid fraction with the coexistence of the solid and liquid phases; consequently, the improved-compatible phase transition heat transfer mathematical model and the corresponding numerical computation method are set up. The new thermal property evaluation indexes which are different from the index of the building envelope with constant thermal property materials are put forward, considering the thermal characteristics of the wall compositing PCM. Combining numerical calculation with experimental test, from the aspects of the thermal property of PCM and the structure configuration inside the PCM wall, the thermal characteristics of the PCM wall is completely analyzed, the effective approaches for improving the thermal performance of wall are obtained, the appropriate type of PCM and wall’s structure configuration under certain climate condition are proposed, and the climate adaptability of PCM wall and its influence on indoor thermal environment are studied. The research of this project will establish the theoretical basis on the numerical calculation of phase transition heat transfer, and is of great significance in revealing the thermal characteristics of PCM wall; meanwhile, it will also provide theoretical basis and data reference for the engineering application of PCM wall.

采用相变复合建筑围护结构，是降低能耗、提高室内舒适度的有效且亟待研究的途径之一。本项目针对相变复合墙体的非稳态、非线性传热过程，采用焓法与有效热容法模型，从相变材料熔化/凝固温区的宽度及重合程度、吸/放热非线性过程、以及固液共存时的液相率等方面，揭示传统模型计算精度的影响机制，建立改进-兼容型相变传热数学模型及相应的数值计算方法；针对相变复合墙体的热特性提出有别于常物性材料围护结构的新的热性能评价指标，将数值计算与实验测试手段相结合，从相变材料热物性参数与相变墙体内部结构形式的角度，系统分析相变墙体的热特性，得到该种墙体热性能提升的有效途径，提出特定气候条件下适宜的相变材料与墙体结构形式，并研究相变墙体的气候适应性及其对室内热环境的影响情况。本项目的研究将为相变传热的数值计算奠定理论基础，对揭示相变墙体的热特性有重要意义，并为相变墙体的工程应用提供理论依据和数据参考。

将相变材料（PCM）放入空心砌块的孔中形成复合PCM空心砌块墙体，则具有应用效果较好、简单且便于施工（与空心砌块成一体）、不占用建筑外墙的厚度、安全性较高（对PCM具有较好的封闭性）等独特的优点。.本研究选取我国典型的空心砌块建筑外墙作为分析对象，将相变材料复合其中，进行相变复合空心砌块墙体的传热实验，对建立的改进型相变传热数学模型进行实验验证；针对相变复合墙体的热特性提出新的热工性能评价指标；将相变复合空心砌块墙体热性能影响因素分为两大类：相变材料的热物性参数（包括相变材料的相变温度、潜热、导热系数等）与相变围护结构内部结构配置（包括相变材料所在的厚度位置、空心砌块每排的孔数/孔宽、相变材料的厚度/排数、各排孔的交错程度等），通过系统地分析得到各因素对墙体热工性能的影响规律；根据所得到的相变复合围护结构热特性，提出特定气候条件下适宜的相变复合围护结构形式；根据所得到的在特定气候条件下适宜的相变复合空心砌块模型，联系相关厂家进行合作；通过实验结合计算的方式对我国不同气候地区典型热环境下复合相变空心砌块墙体的气候适应性进行分析，得到相应气候条件下相变复合空心砌块墙体的适宜的结构形式与相变材料种类，为工程应用提供理论依据和数据参考。