Preparation and characterization of CA-MA eutectic/silicon dioxide nanoscale composite phase change material from water glass via sol-gel method

This work mainly involved the preparation of a nano-scale form-stable phase change material(PCM) consisting of capric and myristic acid(CA-MA) binary eutectic acting as thermal absorbing material and nano silicon dioxide(nano-SiO_2) serving as the supporting material. Industrial water glass for preparation of the nano silicon dioxide matrix and CA-MA eutectic mixture were compounded by single-step sol-gel method with the silane coupling agent. The morphology, chemical characterization and form stability property of the composite PCM were investigated by transmission electron microscopy(TEM), scanning electron microscopy(SEM), Fourier-transform infrared(FT-IR) spectroscopy and polarizing microscopy(POM). It was indicated that the average diameter of the composite PCM particle ranged from 30-100 nm. The CA-MA eutectic was immobilized in the network pores constructed by the Si-O bonds so that the composite PCM was allowed no liquid leakage above the melting temperature of the CA-MA eutectic. Differential scanning calorimetry(DSC) and thermogravimetric analysis(TGA) measurement were conducted to investigate the thermal properties and stability of the composite PCM. From the measurement results, the mass fraction of the CA-MA eutectic in the composite PCM was about 40%. The phase change temperature and latent heat of the composite were determined to be 21.15 ℃ and 55.67 J/g, respectively. Meanwhile, thermal conductivity of the composite was measured to be 0.208 W·m~(-1)·K~(-1) by using the transient hot-wire method. The composite PCM was able to maintain the surrounding temperature close to its phase change temperature and behaved well in thermalregulated performance which was verified by the heat storage-release experiment. This kind of form-stable PCM was supposed to complete thermal insulation even temperature regulation by the dual effect of relatively low thermal conductivity and phase change thermal storage-release properties. So it can be formulated that the nanoscale CA-MA/SiO_2 composite PCM with the form-stable property, good thermal storage capacity and relatively low thermal conductivity can be applied for energy conservation as a kind of thermal functional material.     

A new kind of shape-stabilized phase change materials

Based on the lowest melting point and Schroeder’s theoretical calculation formula,nano- modified organic composite phase change materials(PCMs)were prepared.The phase transition temperature and the latent heat of the materials were 24℃and 172 J/g,respectively.A new shape-stabilized phase change materials were prepared,using high density polyethylene as supporting material.The PCM kept the shape when temperature was higher than melting point.Thus,it can directly contact with heat transfer media.The structure,morphology and thermal behavior of PCM were analyzed by FTIR,SEM and DSC.     

CaCl2·6H2O/EG复合相变材料的制备与性能研究

为了改善六水氯化钙的蓄放热性能,以六水氯化钙为相变材料（PCM）、膨胀石墨（EG）为载体、六水氯化锶为成核剂,采用物理吸附法制备六水氯化钙/膨胀石墨复合相变材料,研究复合相变材料的热物理特性. 采用步冷曲线法,研究复合相变材料的过冷度、蓄/放热性能和热循环稳定性;采用扫描电镜、差示扫描量热法、热流计导热仪,对复合相变材料的显微形貌、相变潜热、相变温度、比热容和导热系数进行测定. 结果表明：在六水氯化钙中添加质量分数为10%的膨胀石墨和质量分数为2%的六水氯化锶,复合相变材料的相变潜热为151.6 J/g,导热系数提升至3.328 W/(m·K),过冷度保持在2 °C以内. 相变材料的导热系数及过冷度得到显著改善.     

圆柱形壳管式相变蓄热单元的释热特性

为了推广太阳能季节相变蓄热热泵供暖系统在寒冷地区的应用,提出了适合该系统的圆柱形壳管式相变材料(Phase Change Material,PCM)贮热单元的结构形式;基于焓法建立了贮热单元的数学模型,并通过数值模拟研究了以CaCl2.6H2O为相变材料的相变蓄热单元的的释热特性及其随换热流体温度和流速的变化规律.研究结果表明:PCM在显热释热阶段温度变化快且释热持续时间短,而在相变潜热释热阶段,PCM温度变化慢且持续时间长;换热流体入口温度越高,释热速度慢且释热量越小.换热流体的流速越大则释热速度越快,流速越小则释热速度越慢.换热流体入口温度与流速是影响圆柱形壳管式相变贮热单元释热特性的重要因素.     

Characterization and thermal conductivity of modified graphite/fatty acid eutectic/PMMA form-stable phase change material

We prepared and characterized a form-stable composite phase change material (PCM) with higher thermal conductivity. Capric acid(CA)-myristic acid(MA) eutectic as core, poly-methyl methacrylate (PMMA) as supportive matrix and modified graphite (MG) powders serving as the thermal conductance improver were blended by bulk-polymerization method. The composite PCMs with different MG mass fraction (2%, 5%, 7%, 10% and 15%) were characterized by FT-IR, SEM, DSC technique and mechanical tests. Thermal conductivities of the composites were measured by transient hot-wire method. The results indicate that MG powders have been successfully inserted into the CA-MA/PMMA matrix without any chemical reaction with each other. The MG/CA-MA/PMMA composites maintain good thermal storage performance while the thermal conductivity has been enhanced significantly. The composite PCM added with 15 wt% MG powders increases approximately as 195.9% in thermal conductivity. Moreover, the thermal conductivity improvement of the composite PCMs is also verified by the melting-freezing experiment, which is profitable for the heat transfer efficiency in latent heat thermal energy storage system.     

MXene/二氧化硅/六水氯化钙复合相变储热材料的制备及性能

六水氯化钙作为一类低温体储热材料, 在蓄热节能方面有着巨大的应用前景。单一的六水氯化钙相变储热材料存在导热系数低和熔化时易泄漏的缺点, 具有较大的内芯和互穿介孔孔道结构的介孔二氧化硅可以解决上述 问题。介孔二氧化硅具有低密度, 热膨胀系数小, 折射率低, 比表面积大等优点, 但其导热系数低, 需要与热性能良好的材料复合来增强导热能力。选用MXene 作为导热增强材料, 在其表面上生长介孔二氧化硅, 再把相变材料六水氯 化钙负载其中。通过综合热分析仪和红外热成像仪测定, 证明复合相变材料的储热性能、热稳定性和传热速率都有显著提升; 在烘箱中观察六水氯化钙的泄漏情况也明显被载体材料所抑制, 成功制备一种热性能和稳定性俱佳的复 合相变储热材料。     

膨润土/月桂酸/鳞片石墨定型储热材料的制备及性能

采用天然膨润土和月桂酸分别作为支撑基体和相变材料,通过真空浸渍法合成复合相变储热材料。结果表明,添加鳞片石墨不仅提高复合相变储热材料的导热特性,而且阻止相变材料从复合相变材料中泄露。制备的复合相变储热材料经历200次热循环实验后,仍具有较好的可靠性,具备在热能存储系统中应用的较大潜力。     

制备工艺对SA/ATTP复合储热材料结构和性能的影响

以硬脂酸为相变材料,以甘肃临泽工业级凹凸棒石为载体,采用热熔法和溶液浸渍法制备了2种硬脂酸/凹凸棒石复合相变储热材料,采用FTIR、XRD、DSC和SEM等手段进行了结构表征和性能测试。结构分析结果表明制备方法对材料的结构和形貌不会产生影响,2种材料具有相似的形貌和结构,SA分别以38.64%和29.13%的比例以物理作用吸附于ATTP表面。性能分析结果表明热熔法和浸渍法制备的复合储热材料其相变温度峰值分别为57.3℃和55.2℃,相变潜热分别为68.71J/g和51.79J/g,均具有较好的储热能力和化学稳定性,且储热能力和SA在ATTP表面的吸附率成正比,但热循环实验表明浸渍法制备的复合材料的热稳定性较差。结合储热性能、储热稳定性和化学稳定性的研究,证明熔融法更适合于制备建筑智能调温和建筑节能相变复合材料。     

含脂酸类相变材料的相变墙板热特性分析

目的进行含脂酸类PCM的相变墙板的热性能分析,探讨其热性能对减少建筑能耗,降低空调负荷的可能性.方法在充分考虑北方地区夏季昼夜的气候条件和国家节约用电的峰谷电价差政策的基础上,利用DSC进行相变储能材料性能测试与分析,优选出两种脂酸类相变材料,制成相变储能墙板,分析其热特性.结果确定了两种分别适合于北方寒冷地区夏、冬季节应用的脂酸类PCM混合物,它们的相变温度在北方地区实际室内空调设计温度范围内,具有很高的相变潜热,把相应的PCM溶入石膏板后具有较高的相变潜热,为充分利用北方地区夏季的夜间自然冷风和峰谷电价差政策提供了先决条件.结论相变墙板不但起到移峰填谷、减少建筑能耗、降低空调负荷、提高经济效益等作用,而且还会大大改善房间的舒适度,为北方地区的空调发展开辟新的空间.     

Role of Composite Phase Change Material on the Thermal Performance of a Latent Heat Storage System: Experimental Investigation

复合相变材料对潜热储能系统中热性能作用的实验研究

Jasim Abdulateef¹, Ahmed F. Hasan^2*,Mustafa S. Mahdi²

（1. 迪亚拉大学 机械工程系,巴古拜 32001,伊拉克;2.迪亚拉大学 化学工程系,巴古拜 32001,伊拉克）

摘要：

石蜡是可用于潜热储能系统单元（LHSU）的理想的相变材料（PCM）。这种潜热储能单元的使用因相变材料导热性差而受到限制。本文采用铝和相变材料制成的金属泡沫生产复合相变材料,以此作为相变材料-潜热储能单元中的导热材料,并使用水作为传热流体（HTF）。通过实验,评估了使用纯相变材料和复合相变材料的潜热储能单元的传热特性。研究包括熔化和凝固过程中相变材料的时变可视化。此外,热存储室内放置一个热电偶网络,记录每个过程的温度分布。结果表明,复合相变材料-潜热储能单元在熔化和凝固过程中均表现出较好的性能。由于金属泡沫的作用,复合相变材料-潜热储能单元的熔化时间比简单的相变材料-潜热储能单元快83%左右,凝固时间减少85%左右。

关键词：相变材料;金属泡沫;潜热;复合相变材料

     

有机相变储热复合材料的储/放热性能研究

以高孔隙率泡沫石墨材料作为骨架在真空环境下吸附石蜡,制备而成新型有机相变储热复合材料。利用HotDisk热常数分析仪和差示扫描量热仪(DSC)研究了其热性能,结果证明复合材料的导热能力得到了极大强化。对分别填充了复合材料和纯石蜡的以水作为热媒的储热槽进行了实验研究,重点考察了两者在储热和放热过程中的温度均匀性、储能速率及泡沫石墨对石蜡相变的影响,同时就泡沫石墨的孔隙率大小对复合材料导热性能和储能速率的影响规律进行了对比分析。研究表明,复合材料的相变温度区间基本不变,导热性能提高了21倍,相变时间缩短了56%以上,相变界面移动加快,储热槽的储热、放热性能和储能密度有了很大提高;不同孔隙率会影响复合材料的导热系数、储能速率和储能容量,在提高储能速率和保证储能容量两者之间,选择孔隙率为91%的泡沫石墨作为复合材料骨架应是一最佳值。     

导热硅胶/相变材料复合组件在电池热管理中的应用

一种低温导热硅胶/相变材料复合组件在电池模组中的使用,有效地解决了相变材料由于液化而发生的析出问题,同时保持相变材料高导热与高潜热值.由于导热硅胶片具有一定的弹性与黏性,使得整个系统具有一定缓冲作用,减少了相变材料与电池之间的接触热阻,进一步提高了整个系统的散热性能.在3C放电倍率下,相比自然冷却方式的66.63 ℃,...     

高温相变储热单元模拟研究与计算

运用Fluent软件对圆形储热单元内部LiCl高温相变材料熔化过程进行二维数值模拟。模拟结果表明：不同位置的LiCl都会出现恒温＂平台＂,其平台的长度和出现的时间间隔随空间位置的不同而有显著差异;随时间的增加,储热单元储热量在相变区明显增大,其储热功率也相应出现了最大值。相变材料的导热系数、相变储热单元的形状和空间尺度以及其恒温隔热装置是改善相变储热系统储热性能的关键性因素。     

复合相变调湿材料的制备与热湿性能

制备一种兼具调热调湿功能的新型复合相变调湿材料（CMPCM）,该材料由相变微胶囊（MPCM）与多孔调湿材料合成。作为被动式节能材料,能够有效平抑室内温湿度波动和降低建筑能耗。其中,相变微胶囊由癸酸和十八烷酸的混合物为芯材、二氧化硅为壁材通过溶胶凝胶法合成,多孔调湿材料为硅藻土。通过扫描电子显微镜（SEM）、差示扫描量热法（DSC）、热重分析法（TGA）,正杯蒸发法和等温吸放湿法分析表征了复合相变调湿材料的组成结构、热性能、热稳定性以及传湿系数和湿缓冲值。DSC和TGA结果显示,复合相变调湿材料比普通相变材料有更小的过冷度和更好的热稳定性。传湿特性实验显示,该新材料比单纯的多孔调湿材料有更大的传湿系数和湿缓冲值。     

正交试验法研究定形复合相变材料的制备工艺

为制备适用于调温纺织品领域的定形相变材料,用溶胶-凝胶法制备了复合相变材料,其中定形材料为以正硅酸乙酯为前驱体通过溶胶-凝胶法制得的二氧化硅凝胶,以月桂酸/十六醇二元低共熔物为相变材料.采用正交试验法研究了溶胶-凝胶法制备复合相变材料的工艺条件.各因素影响复合相变材料的控温能力次序为:酯PCM比>酯水比>pH>反应温度...     

一种新型固-固相变材料及其制备方法

本文根据相变传热的特点,建立了脂肪酸二元体系作为相变蓄热材料的传热模型,通过大量的实验验证了混合体系在融化和凝固过程中的热特性.通过DSC试验,对相变材料的相转变温度、焓变数值以及储热能力进行分析.现巳制备出二元相变体系(月桂酸:癸酸)的相变温度为21.31℃、焓变值153.17 J/g,复合相变体系的相变温度为23....     

Melting intercalation method to prepare lauric acid/organophilic montmorillonite shape-stabilized phase change material

A kind of novel shape-stabilized phase change material (SSPCM) was prepared by using a melting intercalation technique. This kind of SSPCM was made of lauric acid (LA) as a phase change material and organophilic montmorillonite (OMMT) as a support material. And the thermal properties and morphology of the SSPCM were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electronic microscope (SEM), scanning calorimeter (DSC), and differential thermal cravimetry (TG). The DSC result shows that the phase change temperature of the SSPCM is close to that of LA, and its latent heat is equivalent to that of the calculated value based on the mass ratio of LA measured by TG. The XRD, SEM and TEM results demonstrate that the LA intercalates into the silicate layers of the OMMT, thus forming a typically intercalted hybrid, which can restrict the molecular chain of the LA within the structure of OMMT at high temperature. And consequently SSPCM can keep its solid state during its solid-liquid phase change processing.     

复合墙体中相变层相对导热系数计算方法

目前相变材料已初步进入工程应用阶段,由于传热过程受比热、导热系数变化及相变作用的影响,相变材料不能像普通材料一样利用导热系数进行材料比选,其热工设计指标的选择具有一定的困难.为此,提出相对导热系数作为相变材料比选的热物性指标,并给出相应的计算方法用以指导相变墙体的热工设计.在一定环境条件下与定物性材料导热能力相同的导热系数定义为相变应用周期内相变材料的相对导热系数.根据此方法计算得到中国不同地区复合墙体相变层的相对导热系数,通过该参数直观地反映出相变材料层全年的动态传热特性,从而对相变材料在不同地区建筑中的应用效果进行评估.通过将不同相变层的相对导热系数进行对比,得出不同相变材料在建筑中的应用效果差异较大.本文提出的相对导热系数能够为不同环境条件下相变材料的优选进行有效指导.     

Thermal performances of non-equidistant helical-coil phase change accumulator for latent heat storage

Helical-coil is a common structure of heat exchanger unit in phase change heat accumulator and usually has the equal coil pitch between adjacent coils.Its thermal performances Thus,could be improved by improving the uniformity was of unit the phase change material(PCM)temperature distribution.flow a novel non-equidistant helical-coil made structure heat proposed area in this study.Its coil pitch match decreased along the direction of heat transfer fluid,which the exchange in that volume increase to the decreasing temperature difference between was the heat transfer and fluid and PCM.The structure was optimized using numerical simulation.helical-coil temperature An heat experimental accumulator system was developed the experiment results indicated latent the proposed non-equidistant uniformity more effective than equidistant helical-coil for heat storage.The of the distribution was also confirmed by simulation results.     

中温相变蓄热装置的蓄放热性能研究

以相变温度为80℃的相变蓄热装置为研究对象,根据建立的相变传热分析模型,应用数值模拟的方法,研究了蓄热体——相变材料的热物性参数、几何尺寸、填充率,以及热媒体——热水的流速等因素对蓄热装置蓄、放热规律及其特性的影响．研究结果表明,当板状定形相变材料的导热系数在0．4W/(m·K)左右、板厚为8 mm、相变材料的填充率在65%～75%、热媒体流速为5～8mm/s时,蓄热装置可获得较高的蓄、放热效率．