相变蓄能具有温度变化小、蓄热密度大的特点。在建筑中使用相变材料和构件，可充分利用太阳能等自然能源、改善建筑热性能；利用低谷电采暖可减小电网峰谷差，而且在实行峰谷电价的地区，还可节约运行费用。如何在建筑中合理应用相变蓄能材料和构件，以促进建筑节能节资，其应用原理和给定条件下的极限和实际应用效果如何，都是既有学术意义，又有应用价值的研究课题。本文对此进行了理论分析、数值模拟和实验研究。主要学术贡献如下： 提出了被动式理想节能建筑和被动式理想节能建筑围护结构的概念，定义了建筑环境过冷不舒适度Iwin和过热不舒适度Isum。籍此，并利用变分思想，确定了在给定气候条件和建筑内扰情况下，常物性材料和相变材料围护结构达到“被动式理想节能建筑围护结构”的临界热性能，指出了建材热物性设计和控制的方向；给出了Iwin和Isum与建筑围护结构热容和潜热的关系；分析了相变蓄能建筑构件热性能对建筑热舒适性和采暖空调能耗的影响特点，深化了对相变建筑节能原理的认识。 探讨了墙体、地板等相变建筑构件的非线性蓄热、传热特性。与常物性建筑构件对室外温度波动衰减（用衰减系数表示）和延迟（用延迟时间表示）的线性特征不同，相变建筑构件在较窄的温度范围内有大量潜热的吸收或释放，其储传热特性呈现出很强的非线性特征，从而显著影响其温度分布和表面向室内的传热速率。为了评价相变建筑构件对室外温度波动的衰减和延迟效果，本论文提出了表面热流修正因子 和相变穿透时间 ，通过解析和数值分析，以 、 和表面热流密度 作为评价参数，探讨了相变材料热物性对各种相变建筑构件传热特性的影响特点，并做了影响因素的敏感性分析。 在上述研究基础上，对利用太阳能和夏季夜间冷风能的相变建筑围护结构，讨论了其在不同气候地区应用的极限和实际效果；通过解析、数值模拟和实验相结合的方法，研究了建筑中定形相变蓄能地板的使用效果。结果表明，相变建筑围护结构在不同气候地区都可提高室内热舒适性，在寒冷地区和夏热冬冷地区效果最为明显；相变地板能使建筑室温波动大大减小。 提出了利用夜间廉价电采暖的两种定形相变材料蓄热地板系统：被动式系统和送风式系统，通过解析、数值模拟和实验相结合的方法，研究了其设计原则、控制方式、节资效果和在不同气候地区的应用热性能。结果表明，通过合理设计和控制，两种系统能保持采暖季室温舒适、节省运行费用。
Phase change material (PCM) can charge or discharge high latent heat while its temperature keeps unchanged during phase change. By using PCM in building envelope components, a lot of natural energy (such as solar energy) can be effectively applied. For some regions with different electrical price for peak and valley periods, the low-price valley electricity can be effectively applied. In the paper, the following topics are studied: how to use the PCM building envelope components efficiently for energy-saving and money-saving buildings? What are the principles of applying PCM in energy-efficient buildings? What are the ideal and practical effects of applying PCM in energy efficient buildings under the given conditions? They are all very important for academic study and practical application of PCM in energy efficient buildings. In the paper, the following work was accomplished by theoretical analysis, numerical simulation and experiments: Two new concepts ‘passive ideal energy-efficient building’ and ‘passive ideal energy-efficient building envelope’ were put forward. The integrated discomfort degrees Iwin for indoor temperature in winter and Isum in summer were also put forward and applied to evaluate the thermal performance of different building envelope. By using the idea of ‘variation principle’, we got the ideal thermophysical properties of ordinary materials and PCMs for building envelope or building envelope components for given climates and given building internal disturbances, which can point out the direction for building material design and control. The effects of PCM building envelope components to indoor thermal comfort and energy consumption of heating and cooling were analyzed, which can make clear the energy-saving principles for PCM building envelopes. The thermal storage and heat transfer of PCM walls and floor were studied. The ‘decrement factor’ and ‘time lag’, which are used to evaluate the materials with constant thermophysical properties, can’t be used to evaluate the PCM walls, because the melting or freezing of PCM can charge or discharge high latent heat during a narrow temperature range, which causes different temperature distribution in the walls and different surface heat flow into the indoor environment. The modifying factor of surface heat flow and the phase change period were put forward. The two parameters and surface heat flux were used as evaluating parameters. By analysis and simulation, the effects of thermophysical properties of PCM and their sensitivity analysis on various building envelope components were discussed. Based on the aforementioned study, for the buildings with solar energy and night ventilation in summer, the ideal and practical effects of the PCM building envelopes in different climate regions were discussed; the analysis, simulation and experiments were used for analyzing and calculating the effects of shape-stabilized PCM floor in buildings. The conclusions show that the thermal comfort can be improved by PCM building envelopes in different climate regions, and that the effects are most obvious in the cold climate regions and cold-winter and hot-summer regions, and that the PCM floor can decrease the indoor temperature swing in buildings. Two new kinds of floor heating system combined with shape-stabilized PCM and electrical heating at night were put forward: passive floor heating system and floor heating system with air supply. The analysis, simulation and experiments were used for studying the design principles, control methods, money-saving effects and applying feasibility in different climate regions. The conclusions show that the two systems can keep comfortable indoor temperature, save money and be feasible in different climate regions by proper design and control.
