相变储能建筑材料的研究进展

相变储能建筑材料是相变材料与建材基体复合制备的一种新型储能建筑材料。本文分析了相变材料的筛选和改进方法及其封装技术的研究现状,介绍了相变材料与建材基体复合工艺,系统阐述了相变储能建筑材料的作用机理和应用现状,并指出了相变储能建筑材料在实际应用中存在的一些问题,最后展望了相变储能建筑材料的发展前景。     

Synthetic and physical characterization of phase change materials microencapsulated by complex coacervation for thermal energy storage applications

This paper presents a comprehensive study of encapsulated phase change materials (PCMs). In order to investigate some synthesis parameters, microencapsulated paraffin with gelatin/gum Arabic wall system was prepared by the complex coacervation method and the performance of these microcapsules was evaluated by optical microscopy and differential scanning calorimetry. Further investigations were carried out on the impact of physical parameters on the melting time by studying the constrained melting transformation of an encapsulated PCM in a spherical shell subjected to a constant temperature media. Results indicate successful production of PCM microcapsules with high melting enthalpy (116 kJ/kg), and the effects of diameter and thermal conductivity on melting time of PCMs were demonstrated. Copyright © 2014 John Wiley & Sons, Ltd.     

Research and application of microencapsulated phase change materials

相变材料微胶囊很好地解决了相变材料的使用问题.本文介绍了制备微胶囊可采用的芯材和壁材以及它们的优缺点,介绍了相变材料微胶囊化的几种常用方法:原位聚合法,界面聚合法,复凝聚法,悬浮聚合法,喷雾干燥法;总结了相变材料微胶囊在建筑,热流传导,纤维纺织,军事伪装,电子器件冷却等领域的应用;指出了相变材料微胶囊以后的研究目标和方向.     

纳米复合相变材料固液相变储能过程研究进展

对纳米复合相变材料固液相变储能过程的若干最新研究进行了回顾,从相变储能系统的动态性能和典型的凝固、熔化传热过程两方面总结了相关研究的进展,并重点评述了数值模拟研究中纳米复合相变材料有效热物性预测方法的适用性及其与实验结果之间的偏差,最后对纳米复合相变材料固液相变储能过程的未来发展和重点研究方向进行了展望。     

固-液相变贮能材料的研究进展

固-液相变贮能材料具有贮能密度大、相变温度恒定、体积变化小等优点，已成为能源开发利用和材料科学研究的新热点。综述了固-液相变贮能材料的研究现状，介绍了其分类及各类材料贮能性能，并总结了其应用上的缺陷及解决方法。     

Developing microencapsulated 12‐hydroxystearic acid (HSA) for phase change material use

Phase change materials (PCM) have an increasingly more important role as a thermal energy storage (TES) media. However, leakage problem of PCM causes limitation during their integration in TES systems. Therefore, the encapsulation of PCMs is attracting research interest to extend usage of PCMs in real TES applications in recent years. In this study, hydroxystearic acid (HSA) was encapsulated with polymethyl methacrylate (PMMA) and different PMMA comonomer shells via emulsion polymerization method for the first time in literature. HSA with high melting temperature range (74–78°C) can widen the scope of using PCMs, and the encapsulated form can make it more versatile. The chemical structures, morphologies, and thermophysical properties of capsules were determined by FT‐IR, SEM, DSC, TGA, and thermal infrared camera. Among the produced HSA capsule candidates, PMMA‐HEMA is the most promising with latent heat of 48.5 J/g with melting range of 47 to 85°C. SEM analysis indicated that the capsules have spherical shape with compact surface at nano‐micro (100–440 nm) size range; however, some capsules exhibited agglomeration.     

Cooling load reduction in office buildings of hot-arid climate,combining phase change materials and night purge ventilation

Night purge ventilation is a well-known passive technique for conserving cooling energy by storing night coolth in the thermal mass of the building fabric. We study the effect of phase change materials (PCM) as a light thermal mass, on the cooling load of a typical office building with HVAC system and night purge ventilation in hot-arid climate. In this paper the proper conditions to start night ventilation and the ventilation rate by fans is determined. Additionally, the effect of melting point temperature of the PCMs on the cooling load of the building is investigated. PCMs with proper melting temperature were applied to various building elements, and to the whole model. It was revealed that, application of PCMs will significantly contribute in reducing the cooling load, except for the floor on the ground, which resulted in an increase of the load.     

Thermal buffering effect of a packaging design with microencapsulated phase change material

Temperature fluctuations during storage and transportation are the most important factors affecting quality and shelf life of food products. Phase change materials (PCM) with their isothermal characteristics are used to control temperature in various thermal operations. In this study, octanoic acid as PCM candidate was used in a packaging material design for thermal control of a food product. The PCM candidate was microencapsulated in different shell materials in our laboratory. Among the synthesized microcapsules, microencapsulated PCM (mPCM) (ΔHm = 42.9 J/g) with styrene polymer as the shell material was selected based on its properties of being cost effective and compatibility with human health. Thermal buffering effect of PCM in bulk and microencapsulated forms was tested in a packaging design with special PCM pockets. Results showed that packages with mPCM and bulk PCM provided 8.8 and 6 hours of thermal buffering effect for 160 g of chocolate compared with the package without PCM (reference package).     

Thermal properties of 3-hydroxy fatty acids and their binary mixtures as phase change energy storage materials

In the present work, we describe the chemical synthesis of 3-HFAs as prominent derivatives of fatty acids and assess if they could be applied as phase change materials (PCM). In addition, 3-HFAs were obtained by depolymerization of a bacterial biopolymeric material, polyhydroxyalkanoate. Thermal properties of 3-hydoxyoctanoic, decanoic, and dodecanoic acids are reported for the first time. These materials showed the potential to be applied as PCM in temperature range from 33°C to 66°C. In order to expand the temperature range for application of 3-HFAs as PCM, eutectic mass ratios of three kinds of binary mixtures of 3-HFAs were calculated, and their properties were predicted using the Schröder-van Laar equation. Thermal properties of these mixtures were validated by differential scanning calorimetry (DSC) analysis. These results showed that eutectics considerably expanded the scope of applications of 3-HFAs as PCMs. 3-HFAs originating from biotechnologically obtained polyhydroxyalkanoates also showed potential to be applied in development of PCMs.     

Adjustable insulation for enhancing the performance of phase change materials in buildings

The energy savings of a building roof integrated with a phase change material (PCM) and different insulation strategies are presented in this paper. The proposed roof structure includes a concrete slab with a PCM layer and an air cavity insulation, which can be adjusted according to certain strategies. The adjustable insulation is devised to enable a reduced total heat gain throughout 24 h in summer days, thereby improving the performance of the PCM. The heat gain/loss through the roof with the PCM layer and adjustable insulation is compared with that of the roof with the PCM layer and fixed insulation during a typical year in Hangzhou, China. The effects and optimization of the melting temperature of the PCM are also explored. The simulation results show that, overall, the adjustable insulation can reduce the daily heat flux through the roof by approximately 20% compared with the conventional fixed insulation.     

Screening alternatives for producing paraffinic phase change materials for thermal energy storage in buildings

Screening alternatives for producing paraffinic phase change materials (PCMs) from natural gas‐based products was investigated. Based on the quality and cost of these PCMs, two sources were identified: (i) hydrogenated gas‐to‐liquid (GTL) products such as heavy detergent feedstocks; and (ii) linear alpha olefins. Fractionation of a typical hydrogenated GTL mixture, containing C₁₄ – C₁₈ alkene and alkane hydrocarbons, has been experimentally conducted to produce five paraffinic PCMs with melting points between 3 and 28 °C. ChemCAD simulation has been proved to be a valid tool for predicting the behaviour of the GTL fractionation, including optimum experimental conditions and compositions of products. Also, hydrogenation of technical 1‐octadecene was experimentally carried out in order to evaluate the quality of PCM produced from one of the available technical alpha‐olefins. All PCMs produced in this work were analysed by gas chromatography equipped with flame ionization detector to determine their compositions and by differential scanning calorimetry to determine their latent heats. The results showed that the PCM with a melting temperature in the range 22 to 25 °C can be technically produced through hydrogenation of commercial 1‐octadecene showing a higher latent heat compared to the PCM produced from fractionation of hydrogenated GTL mixture. Copyright © 2017 John Wiley & Sons, Ltd.     

Microencapsulation of phase change material with poly(ethylacrylate) shell for thermal energy storage

Microcapsules containing caprylic acid and polyethylacrylate shells were prepared using an emulsion polymerization technique for thermal energy storage applications. Ethylene glycol dimethacrylate was used as a crosslinking agent. The influence of the crosslinking agent concentration on the phase change properties of microcapsules was examined. The caprylic acid microcapsules (MicroPCMs) were analyzed by Fourier transform infrared spectroscopy, thermal gravimetric analysis, scanning electron microscopy, and differential scanning calorimetry. The results showed that microcapsules were synthesized successfully and that the best shell material:crosslinking agent concentration ratio was 1:0.2. The melting and freezing temperatures were measured through differential scanning calorimetry analysis and found to be 13.3 and 7.1°C, respectively. The melting and crystallization heats were determined to be 77.3 and ?77.0 kJ/kg, and the mean particle diameter was 0.64 μm. The thermal cycling tests of the microcapsules were performed for 400 heating/cooling cycles, and the results indicate that the synthesized microcapsules have good thermal reliabilities. Air stability test proved that the thermal properties and physical form of microcapsules were not affected by air. We recommend the prepared thermal, air, and chemically stable caprylic acid microcapsules for thermal energy storage applications as novel microPCM with latent heat storage capacities and properties. Copyright © 2014 John Wiley & Sons, Ltd.     

Recent progress in shape-stabilized phase change materials

定形相变材料是以聚合物为基体,相变物质分布在聚合物三维网状结构中的一种新型相变材料.定形相变材料在相变过程中表现为宏观固相,微观液相,支撑和力学性能优秀,不易泄漏,因其优良的加工性能和安全性能而受到广泛关注,并表现出了广阔的应用前景.本文综述了定形相变材料的制备,导热和阻燃性能等方面的研究进展,并从实验和模拟两方面综合评价了定形相变材料在建筑节能方面的使用性能,展望了定形相变材料的发展前景.     

无机水合盐相变储热材料的过冷性研究

无机水合盐相变储能材料通常存在过冷现象,影响了该类材料所蓄热量的排放性能,如果过冷严重,储存的热量不能释放出来。就无机水合盐的过冷机理及非均匀形核的动力学机理进行了探讨,加入成核剂是降低过冷度的有效措施。     

ZrC nanoparticle-modified microencapsulated phase change materials with enhanced thermal conductivity and photo-thermal conversion performance

A photo-thermal energy storage microcapsule modified by KH550-treated ZrC nanoparticles was prepared via in situ polymerization. ZrC nanoparticles were treated by KH550 to stabilize the paraffin-ZrC emulsion, which could ensure ZrC nanoparticles were incorporated into the microcapsule shell. In this article, microcapsules modified by different mass fractions of modified ZrC nanoparticles (paraffin@MUF-ZrC) were prepared to investigate the influence of ZrC nanoparticles on microstructure, thermal storage, thermal stability, thermal conductivity, and photo-thermal conversion behavior. According to the SEM images, the obtained paraffin@MUF-ZrC microcapsules exhibited good morphology with regular spherical shape and uniform particle size distribution. DSC, TGA, and thermal conductivity analysis were used to characterize the thermal storage properties, thermal stability, and thermal conductivity of paraffin@MUF-ZrC microcapsules, respectively. It showed that these three thermal performance indices improved as the mass fraction of modified ZrC nanoparticles increased. Specifically, the thermal properties of paraffin@MUF-4%ZrC microcapsules were better than paraffin@MUF microcapsules. As a result, specific enthalpy was slightly increased by 14.92% (121.74 J/g) and thermal conductivity increased by 225.16% (0.4962 W/m·K). Moreover, the optical absorption capability also increased. The paraffin@MUF-4%ZrC microcapsules showed remarkable optical absorption capability of 70.23%, which was a 247.67% improvement compared to the 20.20% of the paraffin@MUF microcapsules. Moreover, it was found that paraffin@MUF-4%ZrC microcapsules could heat up from 30°C to 78°C under simulated solar radiation, showing excellent photo-thermal conversion behavior. Based on good thermal storage properties, thermal conductivity, and light absorption capability over the full spectrum, the new photo-thermal energy storage microcapsules have good application prospects in solar thermal conversion and energy storage systems.     

二元有机复合相变材料相变过程热特性实验研究

二元有机复合相变材料因其无腐蚀性、过冷度低、价格低廉和可循环性的优点,在电子器件散热过程中极具发展潜力。通过差示扫描量热法(DSC)测得 4 种脂肪酸和 4 种脂肪醇相变温度与潜热,然后利用准共晶相变理论计算脂肪酸/醇二元有机复合相变材料共晶点,确定 4 种相变温度在 33～37 ℃ 范围内的复合体系,并通过 DSC 实验测量二元体系相变特性。实验结果表明,筛选出的二元有机复合相变材料相变温度分布在 33.08～36.63 ℃,与理论相变温度偏差在0.30%～4.61%;相变潜热分布在 138.5～215 kJ·kg^-1,与理论相变潜热偏差在 0.4%～27%;十二酸与十八醇复合相变材料具有最高的相变潜热(215 kJ·kg^-1),相变温度为 36.5 ℃。研究结果可为有机复合相变材料在电子器件热管理中的应用提供技术参考。     

Phase change materials for building insulation applications

相变材料作为建筑领域重要的保温材料,具有很大的发展潜力.主要综述了相变材料的分类,制备过程,相变保温建筑材料的研究进展,主要应用技术及存在的问题等.相变材料主要包括有机相变材料,无机相变材料和复合相变材料3类.利用物理吸附,微胶囊或高分子包覆封装技术将相变材料封装定形,然后通过一定的复合工艺可将其制成不同的相变保温建筑制品应用于建筑领域,如相变石膏板,相变混凝土,相变砂浆等,并分析了相变材料作为建筑材料的不足.     

Heat transfer of phase change materials (PCMs) in porous materials

In this paper, the feasibility of using metal foams to enhance the heat transfer capability of phase change materials (PCMs) in low- and high-temperature thermal energy storage systems was assessed. Heat transfer in solid/liquid phase change of porous materials (metal foams and expanded graphite) at low and high temperatures was investigated. Organic commercial paraffin wax and inorganic calcium chloride hydrate were employed as the low-temperature materials, whereas sodium nitrate was used as the high-temperature material in the experiment. Heat transfer characteristics of these PCMs embedded with open-cell metal foams were studied. Composites of paraffin and expanded graphite with a graphite mass ratio of 3%, 6%, and 9% were developed. The heat transfer performances of these composites were tested and compared with metal foams. The results indicate that metal foams have better heat transfer performance due to their continuous inter-connected structures than expanded graphite. However, porous materials can suppress the effects of natural convection in liquid zone, particularly for PCMs with low viscosities, thereby leading to different heat transfer performances at different regimes (solid, solid/liquid, and liquid regions). This implies that porous materials do not always enhance heat transfer in every regime.     

金属基相变材料的研究进展及应用

金属基相变材料由于具有储能密度高、热稳定性好、热导率高等优点,在潜热热能储存系统中具有极大的优势。本文回顾了金属基相变材料的发展历程,归纳了金属基相变材料的性能参数,总结了各种热物性的测量方法,探讨了金属基相变材料与容器材料的相容性问题,分析了金属基相变材料在太阳能热发电、工业余热回收和电力削峰填谷中的应用前景。金属基相变材料的高温腐蚀性是目前限制其在热控制中应用的主要因素。为了实现金属基相变材料的广泛应用,需要重点解决金属基相变材料的封装问题。     

Adipic acid-silica composite phase change materials for thermal energy storage:Preparation and characterization

以己二酸为相变材料,二氧化硅溶胶为基体,采用水热法制备己二酸/二氧化硅复合相变储热材料.应用X射线衍射仪(XRD),红外光谱分析(FT-IR),场发射扫描电子显微镜(FE-SEM),同步热分析仪(TG)和差示扫描量热仪(DSC)测试所制备复合材料的显微结构,相变温度和相变焓.结果表明:当反应条件为pH=5,反应温度为150 ℃,反应时间为4 h时,己二酸与二氧化硅之间是简单的物理嵌合关系,复合材料粒径较均匀,平均粒径在1~2 μm;当己二酸的质量分数为30%时,复合材料相变温度峰值为139.0 ℃,相变焓为48.82 J/g;当己二酸的质量分数为50%时,复合材料相变温度峰值为140.5 ℃,相变焓为71.89 J/g.