An experimental study on the phase change behavior of organic phase change materials (PCMs) in porous building materials is reported. Three kinds of porous materials and two kinds of PCMs were used. The phase change behavior of organic PCMs and phase change composites was measured by means of differential scanning calorimetry (DSC). The pore structure of the porous materials was characterized by means of mercury intrusion porosimetry (MIP). X-ray fluorescence spectrometry (XRF) and Fourier transformation infrared spectroscopy (FTIR) were used to characterize the chemical properties of porous materials and phase change materials. Quite different phase change behaviors were found for these two kinds of PCMs in porous materials. For capric acid with a functional group of –COOH, a remarkable elevation of melting temperature was found when confined in porous materials. But for paraffin with only inactive functional groups of-CH2 and-CH3, no elevation or depression of the melting temperature was found when confined in the porous materials. The interaction between functional groups of PCM molecules and alkaline spots on the inner pore surface of the porous materials and the Clapeyron equation were used to explain the different shift of the phase change temperature of capric acid and paraffin in porous materials.

Phase change material (PCM) is a thermal energy storage material with high energy storage density, which can be very useful in the applications of solar thermal energy; such as green buildings, solar thermal power generation and industrial process heat. In this paper, phase change composite was made based on nano-porous graphite and organic PCM, including fatty acids and their derivatives and molecular alloys. Firstly, by means of electrochemical methods, organic functional groups were imported onto the inner surface of nano-porous graphite, which are helpful for the nano-porous graphite to absorb large quantities of organic PCM and keep them safely in its porous space. Then, the thermal properties of the PCM/nano-graphite composite, including the phase change temperature, latent heat and thermal conductivity were studied by means of DSC tests. The nano-porous graphite enhanced the thermal conductivity remarkably, which to date had been a weak point in the applications of PCM. Additionally, the thermal cycling stability of the PCM/nano-graphite composite was observed by means of an accelerating cycling facility and DSC tests. After the processing and characterization, the PCM/nano-graphite composite was encapsulated in aluminum containers and used in the air conditioning system of a pilot green building in Shanghai China, as a tool of thermal storage for the purpose of shifting electrical load of the air conditioning system from peak periods to off-peak periods. Building materials based on the PCM/nano-graphite composite were also developed for the active and/or passive utilization of solar thermal energy in green buildings.

Granular phase changing composites for thermal energy storage were made of granular porous materials and organic phase changing materials by means of vacuum impregnation method. Experimental studies on the vacuum impregnation method, phase changing behavior, chemical compatibility between porous materials and phase changing materials, and sealing performance of coating materials arrived in the following conclusions. Firstly, the vacuum impregnation method is effective in loading porous materials with phase changing materials; and its setup is simple, cheap and easy of scale-up. Secondly, organic phase changing materials (including fatty acids and their derivatives, and paraffin) and inorganic porous materials (including expanded clay, expanded fly ash and expanded perlite) are suitable raw materials for the phase changing composites with respect to chemical compatibility, large thermal energy storage density, and feasibility of large scale processing. Thirdly, thickened latex is the best choice of coating materials for the porous material granules, whose sealing performance is about 40-fold higher than that of normal cement paste and about sevenfold higher than that of the best polymer modified cement paste in this paper.

In this paper, a two-step procedure to produce thermal energy storage concrete (TESC) is described. At the first step, thermal energy storage aggregates (TESAs) were made from porous aggregates absorbing phase changing materials (PCMs). At the second step, TESC was produced with a normal mixing method and using TESAs. An adequate amount of PCM can be incorporated into concrete by the two-step procedure. It can be seen experimentally that the energy storage capacity of the TESC was comparable with that of a commercially available PCM. The experimental results showed that the geometrical features of the porous structure of the aggregates had significant effect on their absorbing ability of the PCM. Aggregates with large pore connectivity factor and transport tunnel in boundary part can absorb more PCM. It was also found that the phase changing behavior was affected by the volume fraction of PCM in concrete.

基于集总参数法和矩形相变等效比热假设建立了相变材料的相变过程温度模型，该模型与实验结果吻合很好，利用该模型定量研究了环境温度、相变潜热、相变温度范围和换热效率等多种因素对相变行为的影响，初步得出如下结论：环境温度对相变开始时间和持续时间均有明显影响，随着环境温度的升高，该二时间呈指数形式下降；相变材料的潜热对相变开始时间没有影响，对相变持续时间有明显影响，持续时间随潜热线性增加；相变温度范围对相变开始时间也没有影响，而相变持续时间随相变温度范围的增加平缓地增加；相变材料与环境之间的换热效率显著影响相变过程开始和持续的时间，二者随换热效率的提高呈指数形式下降。

介绍了制备多孔石墨材料的挤出方法，该法具有连续性、效率高、产品形状多样化、不破坏多孔石墨的孔结构、炭纤维等增强材料定向排列等优点。研究结果表明：增加胶含量会增加多孔石墨的容重，降低其吸附率。而增加用水量则具有相反的效果，即降低多孔石墨的容重，提高其吸附率。孔结构测量结果显示：多孔石墨的孔结构在挤出过程得到了很好的保护，孔空间主要分布在200nm到2000m的孔径范围内，每克多孔石墨含有多达2mL的孔空间。此外，增强材料-炭纤维基本上呈一维定向分布，有利于提高多孔石墨的力学性能。

以多孑L介质和有机相变物质复合而成颗粒型相变储能复合材料，研究了其相变储能性能、耐久性能以及该复合材料在建筑物综合节能方面的功效。研究结果表明：有机相变物质可渗入多孑L介质中从亚微米到数百微米的孔径空间内，占据大部分孑L空间，形成的复合材料具有显著的相变储能功能和优良的耐久性能。复合材料的相变储能性能一方面受到有机相变物质在多孑L介质中体积含量的影响，另一方面受到多孑L介质孑L结构骨架的影响。与传统保温隔热材料-膨胀珍珠岩相比，相变储能复合材料具有更强的建筑综合节能功效。

采用了4种孔结构不同的多孔介质作为有机相变物质的储藏介质，研究了有机相变物质在这些多孔介质中的储藏情况和相变行为，分析了多孔介质的孔结构对有机相变物质的相变行为的调节作用，对于比较纯的有机相变物质。孔结构的调节作用使得相变温度范围宽化。随着储藏量的增加，相变温度移动的幅度增大，但对于成分复杂的有机相变物质，多孔介质孔空间对其相变行为的调节作用比较复杂，甚至会出现截然相反的变化规律。

介绍了微波法制备纳米级多孔石墨的过程。以及采用汞压入法测量该多孔石墨的孔结构。与高温电炉膨化法相比，微波法制备的多孔石墨具有很好的纳米孔隙，孔径分布基本上在4-100nm范围内；而传统的高温电炉膨化的多孔石墨的孔隙直径分布，在纳米扣微波之I|曰]的过渡区域。二者之间存在差别。同时，实验结果显示纳米多孔石墨的孔结构，受到石墨插层物制备时水洗次数（水洗液的pH值）、膨化过程的微波作用时间以及鳞片石墨细度的影响。

用“两步法”，即首先制作相变储能骨料，再采用相变储能骨料，用普通混凝土的制备技术配制了相变储能混凝土。实验结果表明，采用该方法可以在混凝土中储存足够的液体相变材料，配制的相变储能混凝土的储能功能与商业相变材料相当，可以满足实际应用的要求；多孔材料孔结构的几何特征对液体相变材料在多孔材料中的吸收和储存有较明显的影响，具有较高孔隙率、孔结构内部连通性较好和在边界区域具有输运通道的多孔材料能够吸收和储存较多的液体相变材料。相变材料在多孔材料中的体积分数对其相变行为也有显著的影响。