三水合乙酸钠/蛭石复合相变蓄热材料性能优化研究

采用真空浸渍法将三水合乙酸钠（sodium acetate trihydrate,SAT）吸附在膨胀蛭石（expanded vermiculite,EV）微孔内,选择EV吸附SAT能力最佳的质量比为1:6。通过扫描电子显微镜（scanning electron microscopy,SEM）观察复合相变材料（composite phase change material,CPCM）的微观结构,显示EV微孔几乎完全被SAT填充。X射线衍射（X-ray diffraction,XRD）表明SAT与EV化学相容性较好,二者仅发生物理相互作用。通过差式扫描量热法（differential scanning calorimetry,DSC）测试EV在最大吸附能力下,复合材料的相变温度为57.6℃,接近SAT理论相变温度58.1℃;相变潜热为238.8kJ/kg。热重分析（thermogravimetric analysis,TG）结果显示复合材料热稳定性良好。因为EV负载体将SAT间隔为无数微单元,有效改善SAT相变过程中过冷和相分离现象,起到成核剂和悬浮剂的作用。实验研究结果表明,制备的CPCM具有较好的热物性以及稳定的热循环性能,有望成为相变蓄热材料应用于冬季供暖。     

用木屑水解残渣制备活性碳的研究

提出了用木屑水解残渣制取活性碳的设想并加以实验。实验研究了炭化和活化过程中的诸多反应影响因素。在合适的工艺条件下（炭化温度：400℃，炭化时间：60min,活化温度800℃，活化时间：400min，以Ca(OH)2作为添加矿物质），可得到碘值高于620mg/g且得率高于25％的产品。     

高温复合相变材料储热电暖器的储热性能CSCD

本文研究了基于高温复合相变材料的相变储热电暖器,对其储热性能、内部流场和温度分布及温度调控机制进行了实验和模拟研究,并与镁砖显热电暖器的储热性能进行对比。结果表明这类相变储热电暖器的储热平均温度高、平均温差小、出风口温度高,整体性能要优于镁砖显热电暖器。相同体积下两种电暖器储热量相当,但相变储热电暖器的重量可减轻1.6倍;在相同储热时间和储热温度下,同等重量的相变储热电暖器较镁砖电暖器可多储热68%。结果也展示了这类储热电暖器温度控制测点选择的重要性,当选取距离加热单元10 mm处的测点作为温度调控点时,电暖器内的平均温度和储热砖体的最高温度均能满足安全要求,而且加热单元电源在谷电8 h储热过程中只需启停两次。     

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.     

复合相变蓄能材料的研究与发展

本文介绍了复合相变蓄热材料和纳米复合材料的制备、特性、机理及国内外研究现状,并从节能、环保的角度出发,提出将纳米技术与复合相变蓄能材料结合,制备新型、高效的纳米复合蓄能相变材料。     

复合相变材料蓄冷箱的保温性能研究

为了提供医学用品在冷链运输过程要求的低温环境,解决相变材料易泄露和导热系数低的问题,采用熔融共混法制备由十四烷、烯烃嵌段共聚物(OBC)和膨胀石墨(EG)组成的复合相变材料(CPCM)。利用复合相变材料制备蓄冷箱,利用COMSOL软件建立三维数值模型,并对其保温性能进行分析。结果显示：将复合材料应用于蓄冷箱中可以维持2～8℃的温度区间350 min,环境温度为37℃时,蓄冷箱内2～8℃的温度区间也可保持220 min。无源CPCM蓄冷箱系统在高温下也具有较好的保温能力,能够满足短途冷链运输的要求。     

碳捕捉对电石渣-钢渣复合相变储热材料性能的影响

为资源化利用工业固废,降低储热系统成本,选取电石渣和钢渣1∶1混合进行CO₂捕集和封存,将封存CO₂的电石渣-钢渣混合材料作为骨架材料制备7种不同配比的NaNO₃/固碳电石渣-钢渣复合相变储热材料。通过热重分析法探究电石渣-钢渣混合材料的固碳性能,利用差示扫描量热法、高温热冲击法、X射线衍射法、电子显微法表征其储热性能、热循环稳定性、化学相容性和微观结构。结果表明,电石渣-钢渣混合材料的固碳率为24.48%;最佳热性能样品CC-SC4中NaNO₃、电石渣和钢渣的质量比为2∶1∶1,100～400℃工作温度内储热密度达到444.2 J/g,热导率为1.057 W/(m·K),各组分间具有良好的化学相容性;样品CC-SC4经历1440次加热/冷却循环后仍具有优异的储热性能。     

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。     

Na_(2)CO_(3)/电石渣复合相变储热材料制备与性能北大核心CSCD

为循环利用工业固体废弃物,降低储热系统成本,以工业固废电石渣替代传统骨架材料,采用冷压烧结法创新制备7种不同配比的Na_(2)CO_(3)/电石渣复合相变储热材料,利用差示扫描量热法、恒速增压法、电子显微法、高温热冲击法、X射线衍射法、红外吸收光谱法等方法研究其储热性能、力学性能、微观结构、热循环稳定性和化学兼容性。结果表明,电石渣与碳酸钠结合可形成性能优异的复合相变储热材料;电石渣与碳酸钠质量比为52.5∶47.5时制备的复合相变储热材料(NC5)综合性能最佳,储热密度在100~900℃内达到993 J/g,抗压强度达到22.02 MPa,最高导热系数为0.62 W/(m·K);样品NC5中不同组分均匀分布,组分间具有良好的兼容性;样品NC5经100次加热/冷却循环后仍具有优异的储热性能,可为固废资源化利用和低成本储热材料研发提供技术支持。     

石蜡基碳纳米管复合相变材料的热物性研究

以多壁碳纳米管为填料,制备了不同质量分数(1%～5%)的石蜡基纳米复合相变材料。采用差示扫描量热技术对所制备复合相变材料的相变特性进行了表征,其导热性能则通过瞬态热线法导热仪进行了测量。实验结果发现,虽然复合相变材料的相变温度几乎不变,但其相变焓则随碳纳米管的加载量的增加而近似线性下降。在质量分数为5%时,相变焓较纯石蜡下降了约15%。复合相变材料的导热系数大致随温度的升高而降低,而在30和50℃时分别由于固固和固液相变的作用,导热系数测量值出现了较大程度的突增。此外,导热系数随质量分数呈线性增长的趋势,在质量分数为5%时,最大的相对提升率接近40%,展现了良好的导热强化效果。     

An experimental study on the thermal performance of a solar chimney without and with PCM

The thermal performance of a solar chimney without and with phase change material (PCM) has been experimentally studied in this paper. For the case of solar chimney with PCM, three different modes (closed-fully charging mode, open-partly charging mode and open-fully charging mode) were developed. The closed mode was designed to maximize the use of the solar energy when the heating is not required. Whilst the open mode was designed for delivering the heated air to the living space during charging period. The results showed that the inclusion of PCM to a solar chimney would reduce the air flow during charging period but increase it during discharging period compared with the solar chimney without PCM. For the open-partly mode, the mean air flow rate during phase change period was only 0.036 kg/s, which was lower than that for closed-fully charging mode (0.041 kg/s). Regarding the open-fully charging mode, the melting time of the PCM was almost 11 h, which was 57% longer than that for closed mode. The mean air flow rate during phase change period was 0.04 kg/s, which was higher than that for open-partly mode but lower than that for closed mode.     

Structure and thermal properties of expanded graphite/paraffin composite phase change material

Different contents of expanded graphite (EG) composite phase change material (PCM) were prepared by the melt mixing method, taking paraffin as the PCM and EG as the supporting material. Phase compositions of EG, paraffin, and EG/paraffin composite were investigated using X-ray diffraction (XRD). Microstructures of EG and EG/paraffin composite PCMs with different EG contents were observed by a scanning electron microscope (SEM). Thermal properties, such as phase-transition temperature and latent heat of the materials, were determined by differential scanning calorimetry (DSC). Mass loss and thermal properties after 100 heating cycles were measured. The results show that physical absorption exists between paraffin and EG. EG is beneficial for the PCM composite to reduce leakage of paraffin, decrease the phase change temperature and latent heat, and strengthen the thermal stability. The solid–liquid phase change latent heat of materials is larger than that of the solid–solid one. The heating cycle has little effect on the phase-transition temperature and latent heat.     

基于热性能的相变混凝土复合自保温砌块的优化设计

为提高混凝土复合自保温砌块的热工性能,将相变材料填充到砌块中,形成相变自保温砌块。设计了五种相变自保温砌块,采用 ANSYS软件模拟分析不同方案的保温性能,得到最优砌块块型。在此基础上,以西安地区夏季某朝南房间为研究对象,采用 EnergyPlus软件对相变砌块房间展开热环境模拟,研究不同相变温度及相变材料安装位置对室内热环境的影响,探究最优相变层位置及最优相变温度。研究结果表明:孔型为三排交错排列的砌块为最优砌块,其砌筑墙体传热系数为0.439W/(m2·K);夏 季 初 始 室 外 气 温 中 温 时段、中间高温时段以及末期低温时段的最优相变温度分别为24.00、30.00及28.00℃。整个夏季的最优相变温度为26.00~28.00℃,最优相变层位置为砌块内侧孔。对于整个夏季,相变材料安装位置对室内温度的影响高于相变温度的影响,优化设计时应重点考虑。     

用于墙体中的固-固相变材料储热性能的研究

使用固一固相变材料作为墙体中的储能材料不会发生渗漏．能增加墙体的蓄热能力，减小室内温度波动，减少建筑能耗。通过实验研究了多元醇类相变材料组成的二元体系在不同组成下的储热性能，从材料的相变温度和相变潜热分析其应用于墙体中的可行性。研究结果表明：在一定的组成下，多元醇二元体系可达到墙体储能要求的相变温度，且相变潜热较大，是理想的墙体相变储能材料。     

Numerical simulations on performance enhancement of a cross-flow latent thermal energy storage heat exchanger

基于列管式换热器具有传热面积大、结构紧凑、操作弹性大等优点,使其在相变储能领域具有广阔的应用前景。本文建立一种新型列管式相变蓄热器模型,在不考虑自然对流的情况下,利用Fluent软件对相变蓄热器进行二维储热过程的数值模拟。本文主要研究斯蒂芬数、雷诺数、列管排列方式、肋片数以及相变材料的导热系数对熔化过程的影响,并对熔化过程中固液分界面的移动规律进行了分析。模拟结果表明,内肋片强化换热效果明显,特别是对应用低导热系数相变材料[导热系数小于1 W/(m·K)]的列管式蓄热器,相对于无肋片结构,加入肋片（N_fn=2）可缩短熔化时间52.6%。     

Preparation and properties of palmitic acid/SiO2 composites with flame retardant as thermal energy storage materials

Palmitic acid/silicon dioxide (SiO₂) composites with flame retardant as thermal energy storage materials were prepared using sol-gel methods. In the composites, palmitic acid was used as the phase change material (PCM) for thermal energy storage, and SiO₂ acted as the supporting material. In order to improve flame retardant property of the composites, melamine was added in the composites. Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD) and scanning electronic microscope (SEM) were used to determine chemical structure, crystalloid phase and microstructure of palmitic acid/SiO₂ composites, respectively. The thermal properties, such as phase change temperature and latent heat, were investigated by a differential scanning calorimeter (DSC). Thermal stability was determined by a thermogravimetric analyzer (TGA). The SEM results showed that palmitic acid was well dispersed in the porous network of SiO₂. The DSC results indicated that the composites solidify at 59.20 °C with a latent heat of 60.55 kJ/kg and melt at 59.76 °C with a latent heat of 85.11 kJ/kg when the mass percentage of palmitic acid in the composites was 41.1%. The TGA results showed that addition of melamine improved thermal stability. The microstructure of the charred residue after combustion indicated that the homogeneous and compact charred residue decreased the flammability of the composites.     

添加物对石蜡相变螺旋盘管蓄热器蓄热和放热性能的影响

对以石蜡为相变材料的螺旋盘管蓄热器的蓄热和放热性能进行了实验研究,探讨了在石蜡中添加铜粉、硅粉和不锈钢丝带对石蜡螺旋盘管蓄热器蓄热和放热性能的影响。结果表明：在蓄热过程中,随着加热时间的增加,蓄热器内的温度分布不均匀性逐渐增大;纯石蜡蓄热器内温度分布不均匀性最为严重;插入不锈钢丝带的蓄热器内温度分布最均匀。在放热过程中,纯石蜡蓄热器的出口水温下降最快;而石蜡加不锈钢丝带的蓄热器出口水温最高。     

The influence of inner material with different average thermal conductivity on the performance of whole insulation system for liquid hydrogen on orbit storage

At present, several composite insulation systems were proposed that can be used for passive insulation systems, including foam-variable density multilayer insulation (VDMLI), aerogel-VDMLI and hollow glass microspheres (HGMs)-VDMLI. The passive insulation systems with different inner material (IM) showed different performances. However, the relationship between the average thermal conductivity of IM and the insulation performance of the whole system has rarely been investigated. It is of great significance for efficient configuration and matching of the passive insulation system. In this paper, a series of average thermal conductivity of IM were assumed to predict the insulation performance of the whole system at 20 K–300 K and high vacuum. In order to further illustrate the relationship between IM and MLI/VDMLI, the foam was replaced by the HGMs as 5 mm a unit forming a series of HGMs-foam-MLI/VDMLI insulation systems. The performance of the systems was investigated. After the foam was completely replaced by the HGMs, the performance of MLI and VDMLI systems was improved 33% and 13%, respectively. Moreover, each mode of heat transfer including solid conduction, radiation, and gas conduction for foam-MLI/VDMLI and HGMs-MLI/VDMLI insulation systems were calculated and analyzed.     

Study on design and thermal characteristics of vacuum tube solar collector intubated with heat storage tube

In this work, a heat storage vacuum tube solar collector intubated with heat storage tube is designed, which consists of solar vacuum tube, phase change material insert tube, and heat holding cover. The internal energy conversion, transmission, and storage theory are established based on the structure of the heat storage vacuum tube. The parallel and series‐parallel solar air collector system prototype consisting of nine heat storage solar vacuum tube solar collectors is designed and tested. The test results showed that the daily average conversion efficiency of the parallel and series‐parallel prototype reached 56.9% and 48.46%, respectively. Compared with nonheat storage prototype, the heat storage parallel and series‐parallel prototype had higher conversion efficiency by, respectively, 10.9% and 7.8%, longer effective heating time, and better heating stability and practicability. At the same time, the heat storage solar collector has compact structure, which is convenient to use.