脂肪酸二元体系相变贮热性能的研究

用差示扫描量热法研究了月桂酸－棕酸和月桂酸－硬脂酸两个二元体系的固－液相变,发现它们都具有良好的贮热性能,因而是一类有前途的相变贮热材料。     

癸酸-棕榈酸二元复合相变材料的相变特性研究

通过熔融共混法制备一系列二元脂肪酸复合相变材料,并利用步冷曲线法确定癸酸-棕榈酸(CA-PA)二元复合相变材料的最佳质量配比为86∶14,其共晶温度为22.1℃。采用傅里叶红外光谱仪(FT-IR)、冷热加速循环实验和瞬态平面热源法(TPS)等研究CA-PA复合相变材料的结构与性能,发现CA-PA的FT-IR曲线上同时存在CA和PA的特征吸收峰,表明CA与PA是通过分子力作用在一起的。然后对CA-PA进行400次5~80℃冷热加速循环后,发现其相变温度变化不大于0.5℃,可见CA-PA热稳定性良好,且导热系数为0.151 W/(m·K)。同时,根据差示扫描量热仪(DSC)分析得到CA-PA的相变温度和相变潜热分别为21.78℃和154.7 J/g,这与通过步冷曲线得到的共晶温度十分符合,因此该CA-PA复合相变材料适用于建筑节能和热回收领域。     

混合有机材料相变特性实验研究

通过改变混合物的成分配比可以有效地改变混合物物理特性,使其满足某一特定需求。实验研究了一种适用于蓄冷过程的有机混合相变材料,其相变温度范围为６－８℃,具有较好的凝固和熔化特性,没有出现通常的过冷现象,球内实验表明,Ｓｔｅ数和球体直径是影响相变时间的两个重要因素。     

脂肪酸类二元储能材料的相变特性与配比调节北大核心CSCD

针对单一脂肪酸相变温度固定,与实际需求匹配性差的问题,提出以癸酸(CA)、月桂酸(LA)、十四酸(MA)、软脂酸(PA)和硬脂酸(SA)五种常见的脂肪酸作为相变材料,将其两两复合,利用低共融理论计算10种二元复合体系的最低共融点和理论质量配比,通过熔融共混法制备二元低共融复合体系并在其低共熔点上下3%~6%调节质量配比,借助DSC测试二元低共融复合体系的相变特性。结果表明,二元低共融体系的理论相变温度范围为21.58~53.90℃,理论相变潜热范围为157.64~191.85 J/g,与五种单一脂肪酸的热性能相比,相变温度降低了约10~15℃,相变潜热值无明显变化;制备的10种二元低共融体系的相变温度范围为19.94~56.49℃,与理论相变温度偏差为1.93%~14.72%;相变潜热为125.78~181.45 J/g,与理论相变潜热偏差为0.18%~19.86%;其中CA二元体系的理论相变温度范围为21.58~30.11℃,适用于建筑节能领域;LA二元体系的理论相变温度范围为35.87~41.15℃,适用于电子器件热管理或调温纺织品领域;MA和PA二元体系的理论相变温度范围为46.05~53.9℃,适用于大体积混凝土温控领域;在低共熔点附近调节配比发现最佳配比与理论计算的低共熔配比偏差在4%以内,验证理论计算的准确性和可行性。本研究结果可为脂肪酸类二元复合相变材料的具体使用范围提供技术参考。     

新型相变贮热材料

在太阳能热利用、工业余热回收、采暖及空调领域中 ,为了调整热能供应与人们需求之间的不一致 ,热能的贮存是极为关键的一环。目前普遍使用的贮热方式有两大类 :显热式贮热和潜热式贮热。所谓显热式贮热 ,就是通过加热介质 ,使其温度升高而贮热 ,它也叫“热容式贮热”。潜热式贮热是利用贮热介质被加热到相变温度时吸收大量相变热而贮热 ,它也叫“相变式”贮热。物质由固态转变为液态（熔解） ,由液态转变为气态（气化） ,或由固态直接转变为气态（升华） ,都会吸收相变热 ;而进行逆过程时则释放相变热。这是潜热式贮热所依据的基本原理 ,在…     

热适应复合相变材料的制备与热性能

根据电子器件散热技术领域对热适应复合材料的性能要求,选取导热系数高且密度低的膨胀石墨作为无机支撑材料,石蜡作为有机相变材料,制备出高导热系数和储热密度的热适应复合相变材料.采用扫描电镜(SEM)、差示扫描量热仪(DSC)、偏光显微镜(POM)和Hot Disk热常数分析仪等多种测试技术,对复合相变材料进行分析研究;通过储/放热实验和1000次热循环实验研究了复合相变材料的传热性能和热稳定性.实验结果说明该复合相变材料具有形状稳定、导热率高、储热密度大等特点,并具有良好的热稳定性和使用寿命.     

非理想相变特性材料热性能简化分析方法及适用条件

采用焓法、分析了蓄能相变材料相变区比热特性性对其蓄换热性能的影响。该方法对潜热型蓄换热系统的热性能分析和计算是普适的。针对该方法较为复杂而理想相变材料（相变温度为一点）热特性的分析较为简单并有大量结果可供参考的特点，讨论了采用对理想相变材料适用的蓄换热性能分析方法和公式来计算相变温度为一个温度区间的非理想相变材料蓄换热特性的适用条件。所得结论拓宽了理想相变材料蓄换热性能分析方法及结果的适用范围。在很多情况下，大大简化了非理想相变材料蓄换性能的分析和计算，对各种蓄能相变换热器的设计和性能优化具有指导意义。     

组合相变材料储热的实验研究

分析了在同一储热系统中采用两种或两种以上相变材料的特点,介绍了用于组合相变材料储热研究的实验装置,给出了四种相变材料水平柱状储热单元储热系统的初步测试结果,并对其进行了讨论。     

相变贮热材料的DSC研究

用ＤＳＣ法研究了多元醇，层状钙钛矿等几种相变材料的热物理性能，它们都是有希望的贮热材料，实验所得数据是评价和选择这些材料的主要依据。     

Electrospun ultrafine composite fibers of binary fatty acid eutectics and polyethylene terephthalate as innovative form‐stable phase change materials for storage and retrieval of thermal energy

In this study, four fatty acids of lauric acid (LA), myristic acid (MA), palmitic acid (PA), and stearic acid (SA) were selected to prepare six binary fatty acid eutectics of LA‐MA, LA‐PA, LA‐SA, MA‐PA, MA‐SA, and PA‐SA; thereafter, electrospun ultrafine composite fibers with the binary fatty acid eutectics encapsulated in the supporting matrices of polyethylene terephthalate (PET) were prepared as innovative form‐stable phase change materials for storage and retrieval of thermal energy. The morphological structures and thermal energy storage properties of the ultrafine composite fibers were characterized by scanning electron microscope (SEM) and differential scanning calorimeter (DSC), respectively. The SEM results indicated that the fibers had the cylindrical morphology with diameters of 1–2 µm; some had smooth surfaces, while others had wrinkled surfaces with grooves. The DSC results indicated that the phase transition temperatures of binary fatty acid eutectics were lower than those of individual fatty acids; the enthalpy values associated with melting and crystallization for the eutectics encapsulated in the composite fibers were considerably reduced, whereas there were no appreciable changes on the phase transition temperatures. Copyright © 2012 John Wiley & Sons, Ltd.     

Theoretical study on a novel phase change process

This paper mainly deals with a novel homogeneous phase change process in materials (HPCP). The HPCP is analysed in detail and the expressions for one‐dimensional HPCPs are derived. It is concluded that, compared with the conventional phase change processes, the complete phase change time of HPCPs can be decreased by 60% for a spherical phase change material (PCM), 50% for a cylindrical PCM and 33% for a flat plate PCM, respectively, and the application of HPCPs to thermal energy storage systems can charge or discharge thermal energy with constant rates. Possible applications of HPCPs to thermal energy storage are simulated and further discussed using composite flat plate PCMs. Copyright © 1999 John Wiley & Sons, Ltd.     

Experimental and numerical investigation of the melting process and heat transfer characteristics of multiple phase change materials

The melting and heat transfer characteristics of multiple phase change materials (PCMs) are investigated both experimentally and numerically. Multiple PCMs, which consist of three PCMs with different melting points, are filled into a rectangle-shaped cavity to serve as heat storage unit. One side of the cavity is set as heating wall. The melting rate of multiple PCMs was recorded experimentally and compared with that of single PCM for different heating temperatures. A two-dimensional mathematical model to describe the phase change heat transfer was developed and verified experimentally. The properties of multiple PCMs, including the effect of the melting point difference (combined type), thermal conductivity, and latent heat, on the heat transfer performance of the PCM were analyzed numerically. The results show that, the melting time decreases before it increases, with an increasing melting point difference for the multiple PCMs. In addition, the melting point decreases with increasing distance from the heating wall. Most of these types of multiple PCMs melt faster than the single PCM, and the multiple PCMs, with the melting point arranged as 322 K/313 K/304 K, has the shortest melting time in this study. The melting rate of the multiple PCMs, 322 K/313 K/304 K, accelerates faster than for the single PCM as the thermal conductivity, latent heat, and heating wall temperature increase. Finally, generalized results are obtained using a dimensionless analysis for both single and multiple PCMs.     

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。     

Modification on hydrated salt‐based phase change composites with carbon fillers for electronic thermal management

For electronic thermal management with hydrated salt phase change materials (PCM), supercooling and thermal stability usually inhibit its development. In view of this, novel of disodium hydrogen phosphate dodecahydrate (DSP)‐based composites PCM with miniaturized size is developed to solve these problems. Three kinds of carbon fillers employed as both nucleating agent and heat transfer promoter were added in DSP separately. The influences of carbon fillers' specific surface area, particle size, and adsorption mode on thermal properties of DSP‐based composites PCM were investigated experimentally. The thermal conductive chains of composites PCM were detected by energy dispersive spectroscopy. The supercooling degree was analyzed by melting‐freezing test. Temperature‐regulated property was captured by infrared imager. In the present work, the supercooling degree of GNS/DSP composites PCM is efficiently reduced to 97.24% compared with the pure DSP. Negligible change in phase change temperature of the CNTS/DSP composites PCM was confirmed after 200 times cycles. There was no obvious liquid leakage of DSP when 2 wt% of carbon fillers were added in composites PCM. The enhancement on thermal properties of DSP is a promising strategy for numerous thermal applications.     

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。     

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.     

带相变蓄热小型热泵冷凝热回收性能实验研究

通过实验初步研究了采用光管螺旋相变蓄热器替代传统水蓄热器的小型家用热泵冷凝热回收系统的性能,对相变蓄热和水蓄热的冷凝热回收过程进行了对比实验,分析并得到了两类冷凝热回收系统的性能参数及综合能效系数。实验数据表明:与水蓄热系统相比,光管螺旋相变蓄热器体积减小,并且系统运行较传统水蓄热工况下更加平稳,但存在传热效果较差、热回收率低的缺点,回收率仅为15%,系统综合能效系数2.9。可知,相变蓄热器的内部结构对系统综合能效系数影响很大。     

Study on preparation and thermal property of binary fatty acid and the binary fatty acids/diatomite composite phase change materials

This study prepared a series of binary phase change materials by mixing decanoic acid, dodecanoic acid, hexadecanoic acid and octadecanoic acid each other. The phase-transition temperature of binary fatty acid and its corresponding mixing proportion are calculated with phase diagram thermodynamic method. The results are verified by the experimental result of the heat absorption curve and the Differential Scanning Calorimetry (DSC) analysis curve. The results show that the calculation method of phase diagram thermodynamic calculation can be taken as a basis for mixing proportion of binary fatty acid phase change materials. In addition, the decanoic–dodecanoic acid/diatomite composite phase change material (PCM) are prepared and its microstructure, thermal property and thermal reliability are characterized. The result shows that the decanoic–dodecanoic acid is uniformly adsorbed into diatomite and the form-stable PCM are formed. The phase-transition temperature and the latent heat of the decanoic–dodecanoic acid/diatomite composite PCMs is 16.74 °C and 66.8114 J/g, respectively.     

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。