Review on phase change materials based battery thermal management technology

因环保和节能的需要,电动汽车必将成为未来汽车发展的重要方向。影响电池性能、寿命的热管理技术近年来发展迅速。电池热管理根据其传热介质分为空气冷却技术、液体冷却技术和相变材料冷却技术。本文根据近年来国内外对基于相变材料的动力电池热管理研究状况,综述了电池热管理相变材料的研究进展,重点总结了用于电池热管理的相变材料、PCM/高导热粒子、PCM/泡沫金属以及PCM用于电池热管理的形式。     

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。     

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。     

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。     

改进的VIKOR决策模型在大隆水库汛期水位动态控制中的应用

针对传统VIKOR法在权重确定方面的不足,提出了基于权重搜索技术的VIKOR决策模型,该模型通过改进云模型计算主观权重和critic法计算客观权重,以其作为可行域边界,利用权重搜索技术进行寻优,得到将主客观权重相耦合的综合权重,并输入VIKOR决策模型进行计算。大隆水库汛期运行水位动态控制方案决策结果表明,改进的VIKOR决策模型在权重确定时既考虑了专家主观经验又考虑了客观数据特点,结果兼具全面性和科学性。通过设置不同的决策机制系数可得到决策者处于不同心理下的方案排序结果,在解决了大隆水库汛末蓄水量不足问题的同时,验证了该模型的适用性和可行性。     

Multicriteria renewable energy planning using an integrated fuzzy VIKOR & AHP methodology: The case of Istanbul

The purpose of this study is twofold: first, it is aimed at determining the best renewable energy alternative for Istanbul by using an integrated VIKOR-AHP methodology. Second, a selection among alternative energy production sites in this city is made using the same approach. In the proposed VIKOR-AHP methodology, the weights of the selection criteria are determined by pairwise comparison matrices of AHP. In energy decision making problems, the judgments of decision makers are usually vague. As it is relatively difficult for decision makers to provide exact values for the criteria, the evaluation data for the alternative energy policies should be expressed in linguistic terms. In order to model this kind of uncertainty in human preferences, fuzzy logic is applied very successfully. Thus, both classical VIKOR and classical AHP procedures are performed under fuzzy environment. The originality of the paper comes from the application of the proposed integrated VIKOR-AHP methodology to the selection of the best energy policy and production site. It is found that wind energy is the most appropriate renewable energy option and Çatalca district is the best area among the alternatives for establishing wind turbines in Istanbul.     

格子Boltzmann方法模拟泡沫金属内相变材料热传导融化传热过程

基于局部热非平衡条件下泡沫金属内热传导融化相变传热的非线性双温度方程,在表征单元尺度上构建双温度分布函数格子Boltzmann模型,其中相变非线性源项处理采用焓法迭代求解。数值模拟了金属骨架与相变材料的温度分布情况,重点分析了孔径、金属骨架与填充材料热传导比和Stefan数等对局部热非平衡效应的影响。模拟结果表明,孔径越大、金属骨架与填充材料热传导比越大,局部热非平衡效应越明显;相变过程的存在,加大了局部热非平衡效应,并且Stefan数越低局部热非平衡效应则越大。     

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.     

Preparation and characterization of polyethylene glycol/active carbon composites as shape-stabilized phase change materials

Shape-stabilized phase change materials (PCMs) composed of polyethylene glycol (PEG) and mesoporous active carbon (AC) were prepared by a blending and impregnating method. Various techniques were carried out to characterize the structural and thermal properties of the composites. Lower phase change temperatures and enthalpies were observed as the weight percentage and molecular weight of PEG was decreased. The crystallinity of PEG in the PCMs decreased with the increase in the AC content. The activation energy of the PEG phase change decreased with higher PEG weight percentages. We conclude that the phase change properties of the PEG/AC PCMs are influenced by the adsorption confinement of the PEG segments from the porous structure of AC and also the interference of AC by acting as an impurity with perfect PEG crystallization.     

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.     

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.     

复合相变储能材料的传热性能研究进展

总结近年来国内外相变储能材料的研究状况,包括相变储能材料的制备、传热性能、相变过程数值模拟和应用等,并对复合相变储能材料的传热性能研究方法的前景作了展望。     

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.     

石蜡基复合相变储热材料的导热性能

为提高石蜡作为固-液相变储热材料的导热性能,在石蜡(PW)中掺加高导热系数的碳纳米管(CNTs),制备了碳纳米管-石蜡复合相变材料(PW-CNTs).为进一步增强PW-CNTs的传热性能,通过内置金属网结构,利用金属网的高导热性,加快PW-CNTs作为相变材料的充放热速率.测试了PW-CNTs的熔点和相变潜热、导热系数以及置入金属网前后的充放热时间.结果显示,PW-CNTs的导热系数较石蜡得到显著提高,其中掺加10％(质量分数)CNTs的复合材料的固态、液态导热系数平均分别提高31.4％、40.2％.置入金属网结构后,PW-CNTs的充放热时间至少分别缩短了40.3％和30.2％.此外,碳纳米     

Recent progress in diatomite based composite phase change materials for thermal energy storage

硅藻土是一种含量丰富的非金属矿,具有较高的孔隙率,良好的表面结构和热物理性能,因而可作为复合储热材料的载体.本文综述了复合储热材料的种类和制备工艺,并介绍了硅藻土的结构,性能和以硅藻土为载体的复合相变储热材料的研究及应用现状.     

区间数不确定性多属性决策方法应用研究

基于区间数的“”运算,给出一个解决属性权重和决策矩阵元素都为区间数的不确定多属性决策问题的方法,并给出模型。用该方法进行决策时,属性权重直接以区间数的形式参与计算,与具体的属性权重无关,减弱了属性权重的影响。最后通过实例,证明了该方法的可行性。     

Preparation and properties studies of halogen-free flame retardant form-stable phase change materials based on paraffin/high density polyethylene composites

The halogen-free flame retardant form-stable phase change materials (PCM) based on paraffin/high density polyethylene (HDPE) composites were prepared by using twin-screw extruder technique. The structures and properties of the form-stable PCM composites based on intumescent flame retardant system with expandable graphite (EG) and different synergistic additives, such as ammonium polyphosphate (APP) and zinc borate (ZB) were characterized by scanning electronic microscope (SEM), thermogravimetric analyses (TGA), dynamic Fourier-transform infrared (FTIR) spectra, differential scanning calorimeter (DSC) and Cone calorimeter test. The TGA results showed that the halogen-free flame retardant form-stable PCM composites produced a larger amount of charred residue at 700 °C, although the onset of weight loss of the halogen-free flame retardant form-stable PCM composites occurred at a lower temperature due to the thermal decomposition of flame retardant. The DSC measurements indicated that the additives of flame retardant had little effect on the thermal energy storage property, and the temperatures of phase change peaks and the latent heat of the paraffin showed better occurrence during the freezing process. The dynamic FTIR monitoring results revealed that the breakdowns of main chains (HDPE and paraffin) and formations of various residues increased with increasing thermo-oxidation temperature. It was also found from the Cone calorimeter tests that the peak of heat release rate (PHRR) decreased significantly. Both the decrease of the PHRR and the structure of charred residue after combustion indicated that there was a synergistic effect between the EG and APP, contributing to the improved flammability of the halogen-free flame retardant form-stable PCM composites.     

Experimental determination of the effective thermal capacity function and other thermal properties for various phase change materials using the thermal delay method

The recently presented thermal delay method is an improved version of the well-known T-history method, which is widely used for thermal properties measurement of phase change materials (PCM). The most important difference between the thermal delay and the T-history methods is that the former is based on the use of thermal delay (i.e. temperature difference) between PCM and a reference fluid at any specified time while the latter makes use of their time delay at any specified temperature. Although the thermal delay method has been documented in our previous publication, measurements are performed of the known and indisputable values of ethyl alcohol thermal capacity and the latent heat of the double distilled water (WFI), which confirm the accuracy of the method. Additional comparisons with values provided by PCM producing companies show disagreements lower than 1.7%. The main volume of measurements of the present study includes the following thermal properties of various practically interesting PCM: (a) the temperatures at the ends of the two-phase region; (b) the liquid and solid PCM thermal capacities; (c) the phase change heat; (d) the heat storage capacity during any specified temperature range; and (e) the effective thermal capacity function, which is a very important and useful property for practical applications. The above function is provided for each one of the PCM examined in the form of diagrams, as well as in the form of analytical expressions derived by curve fitting to the processed experimental values. All measurements were repeated 20 times and the results were averaged in order to minimize errors from accidental incidents.     

Thermal management of lithium-ion batteries using phase change materials

良好的热管理系统是电池安全及高效使用的保证,电池的热管理需要确保电池温度在安全温度范围以及电池组内最大温差不超过5 ℃.传统的热管理方式,如空气冷却,不仅需要额外的动力输入,而且越来越不能满足高能量密度的新型锂离子电池的热管理需要.使用相变材料的电池热管理系统,利用相变材料的相变潜热吸收电池产生的热量,在不使用外界功耗的条件下,可以长时间保持电池的温度在适宜的范围内.通过与膨胀石墨,金属泡沫复合,相变材料的热导率可以大大提高,电池组内体系温度均匀性可以满足工作要求.而且,相变材料的形状不固定,可以使用在任意形状的电池上.被动式热管理是应用于电池热管理系统中最具前景的技术.     

水电工程施工方案的模糊优选

采用层次分析法(AHP)确定施工方案中的目标权重;应用多目标模糊决策模型,考虑专家经验,通过定性与定量有机结合的分析方法对施工方案的优劣进行合理的排序,解决水电工程施工方案的优选问题。最后以某大型引水工程施工方案优选决策的实例结果来表明模糊优选法的客观性和实用性。