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。     

应用于日光温室墙体的相变材料热物性优化研究

建立日光温室计算传热模型,以室内空气温度和墙体内表面温度为指标,通过实验方法验证了所建立的传热模型准确性,最后分析相变材料相变温度、相变焓、导热系数、密度等热物性对室内最低温度和相变蓄热率的影响规律,确定被动式相变蓄热墙体和主-被动式相变蓄热墙体的最佳相变材料热物性,阐明了实际应用时相变材料选择原则。研究结果表明,所建立的日光温室传热模型具有较高准确性,可用于日光温室墙体相变材料热物性优化;主-被动式相变蓄热墙体最佳相变材料的相变温度为27 ℃,相变焓为200 kJ/kg,导热系数为0.35 W/（m·K）,密度为440 kg/m³,被动式相变蓄热墙体最佳相变材料的相变温度为26 ℃,相变焓为200 kJ/kg,导热系数为0.35 W/（m·K）,密度为792 kg/m³;最佳相变材料热物性应用时,2种墙体室内最低温度均可达到15.0 ℃,但是被动式相变蓄热墙体的相变蓄热率较主-被动式相变蓄热墙体减小29.5%。本研究可为相变材料在日光温室的高效利用提供参考。     

Fundamental scientific aspects of lithium batteries (III) --Phase transition and phase diagram

相变是电池材料基础研究中的重要问题.对材料相变的准确认识,有利于合成制备过程中获得晶体结构与组成符合设计要求的目标材料.了解电解质中的相变可以知道其使用的安全稳定条件,利用其相变性质发展新的电解质材料.相的组分与相变趋势可以由相图简明直观地展示出来.本文小结了与锂离子电池相关的相变与相图研究.     

墙体储能用定形相变石蜡储热性能的实验研究

实验配制并研究了以高密度聚乙烯为支撑材料的定形相变石蜡.所使用的石蜡为由液体石蜡分别与46#石蜡、48#石蜡配制的两种适于墙体中使用低熔点混合物,相变温度分别为26.6、25.5℃,相变潜热较大.利用DSC实验研究了两种石蜡混合物分别与高密度聚乙烯按40%～90%比例配制成的定形相变材料的相变温度、相变潜热、均匀性和稳定性.定形相变材料在低温区的相变温度与石蜡的相变温度基本一致,在26～28℃之间,定形材料相变潜热近似等于石蜡的相变潜热与石蜡百分含量的乘积.定形相变材料中石蜡的最佳含量为70%,此时相变潜热约为100J/g.     

Influence of annealing treatment on Laves phase compound containing a V-based BCC solid solution phase—Part I: Crystal structures

Two multi-component Laves phase hydrogen storage alloys containing a body centered cubic (BCC) solid solution phase were prepared and the effects of annealing treatment on their crystal structures have been studied in this part. It is found by X-ray powder diffraction and energy dispersive X-ray spectrometer analysis that the as-cast alloys mainly consist of two phases: the C14 Laves phase matrix with hexagonal structure and the dendritic V-based solid solution phase with BCC structure. In addition, a small amount of TiNi-based third phase is also found precipitated within both the C14 Laves phase and the V-based solid solution phase. However, the content of the TiNi-based phase is decreased greatly by an appropriate annealing treatment owing to the compositional homogenization. Furthermore, the lattice parameters and unit cell volumes of both the C14 Laves phase and the V-based solid solution phase have all increased after the annealing treatment.     

Influence of partial substitution of Mo for Cr on structure and hydrogen storage characteristics of non-stoichiometric Laves phase TiCrB0.9 alloy

The influence of the partial substitution of Mo for Cr on phase composition and hydrogen storage characteristics of non-stoichiometric Laves phase TiCrB_0.9-based alloys is investigated by X-ray diffraction (XRD), pressure composition isotherm (PCT), and scanning electron microscopy (SEM) characterizations. XRD tests reveal that the phase composition of the alloys gradually changes from single TiB_1.07CrB_1.93 Laves phase to the co-existence of Laves phase and Mo-based BCC phase with increasing substitution of Mo for Cr. The phase composition eventually transforms into a single Mo-based BCC phase when the amount of the substitution surpasses a certain level. PCT tests reveal that the maximum hydrogen storage capacity increases with increasing Mo content. The hydrogenation-induced phase changes are also greatly influenced by the substitution of Mo for Cr. SEM tests of the hydrided alloys show that the increasing Mo content enhances hydrogenation-induced pulverization. Finally, hydrogenation-induced phase changes during the course of activation are also investigated.     

汽液相变系统的平衡稳定性分析

以非平衡热力学理论为基础,通过引入可用能这个汽液相变换热过程的一个重要的功势函数,对汽液相变系统的可用能进行了分析,得到了汽液相变系统的可用能变化的计算式,并以此为判据来分析汽液相变系统的稳定性,得到了汽液相变系统的相平衡条件、力学稳定性条件和热稳定性条件。并给出了有关物理意义;定义了汽液相变时的汽、液相的力稳边际曲线。结果表明,汽液相变系统的力稳条件不同于简单可压缩单相系统的力稳条件,相变力稳边际曲线是相变时不可逾越的界限。     

两相流垂直下降横掠"T"形柱体的斯特罗哈数

试验研究了两种规格梯形柱体，在垂直下降气液两相流中，发生气液两相涡衡时，气液两相特斯罗哈数的变化规律。在测得大量数据的基础上，得出了发生气液两相涡街时，气液两相斯特罗哈数的通用关系式。研究表明，气液两相斯特罗哈数在两相工况下为一变数，与来流截面含气率、涡街发生体形状与特征尺寸和来流方向等因素有关。应用此关系式，根据测得的两相涡街频率可将涡街发生体作为测量两相流流量与组分的测量元件。     

季节性冻土区同沟原油成品油管道的周围土壤温度场

在季节性冻土区,由于冬季气候寒冷,土壤中水分冻结发生相变.为了研究冻土区发生冻结对同沟敷设原油和成品油管道周围土壤温度场的影响,采用非结构化有限容积法对同沟敷设埋地管道周围土壤温度场进行模拟计算.模拟不考虑冻结相变和考虑冻结相变两种情况下的温度场,分析发现在冻结很长一段时间内,由于土壤中水分释放大量的相变潜热考虑相变情...     

亚临界压力下两相流动时截面含气率的测量

两相流参数的检测对于工程实际应用和两相流的理论研究有着十分重要的意义。作者对亚临界压力下两相流动时的截面含气率进行了深入的实验研究,获得了大量的实验数据,为两相流动参数的检测及理论研究提供了可靠的资料。图６参４     

纳米Fe2O3/硬脂酸/十八醇纳米复合相变蓄热材料的性能研究

针对有机相变材料热导率低的问题,将高热导率的纳米Fe₂O₃添加到硬脂酸/十八醇二元有机复合蓄热相变材料中,制备纳米复合蓄热相变材料。从分散剂的种类、分散剂与纳米材料的添加量以及超声时间4个方面研究其对纳米复合相变蓄热材料的稳定性及热物性的影响。结果表明,阴离子表面活性剂的分散效果优于阳离子和非离子表面活性剂。复合相变材料中添加质量分数为0.8%,十二烷基苯磺酸钠(SDBS)和质量分数为0.4%Fe₂O₃的体系,超声时间为80 min时,纳米Fe₂O₃在相变材料中的分散效果最好。添加纳米Fe₂O₃后复合蓄热相变材料的相变潜热及相变温度有所下降,热导率提高34.9%。300次热循环复合相变材料的相变温度波动区间不超过0.41℃,相变潜热波动区间不超过4.0%,热稳定性良好。     

喜河水力发电厂3号发电机的进相运行与试验

电力系统中采用电机进相运行(欠励),是平衡无功、调节电压最简便、经济的措施。由于发电机进相运行受到一些因素的限制,在发电机采用进相运行前,应对发电机进行进相运行能力试验,确定发电机进相深度,确保发电机进相运行时的稳定安全。     

正交各向异性相变材料的无网格法传热模型及应用

利用无网格迦辽金(EFG)法建立正交各向异性相变材料的传热计算模型,基于该模型编程完成各向异性材料太阳能相变蓄热水箱和管壳式相变蓄热单元的相变传热分析,并探讨热导率因子和材料方向角对复合材料相变传热特性的影响.研究表明:在相同节点布置下EFG法的温度场和相界面计算精度均高于有限元法,EFG法在动态相界面追踪方面具有明显...     

用录波分析软件分析主变差动动作原因

针对110 kV万茜变电站35 kV侧线路遭受雷击,线路保护电流一段动作现象,使用录波分析软件分析故障前的电流相位、差动动作值和C相动作轨迹.在分析主变差动保护动作原因的基础上,得出了在单相接地故障状况下,主变高压侧出现三相电流幅值基本相同以及相位基本一致的结果.证实了此次故障是一起典型的B相区外故障,差动B相可靠不动;C相区内故障,差动C相正确动作.C相区内故障,主要是一体化电流互感器遭受高电压,绝缘被击穿,导致区内C相接地.通过分析主变差动动作原因和总结经验,提出改进措施,旨在更好地完善变压器保护的运行和维护.     

相变储湿纤维的制备及其形貌影响因素的研究

醋酸纤维素为包裹材料、聚乙二醇800为相变材料、N,N-二甲基乙酰胺和丙酮为溶剂,采用静电纺丝法制备具有调温调湿性能的相变储湿纤维。采用电子扫描电镜(SEM)对相变储湿纤维进行表征,系统分析相变材料用量、聚合物用量、溶剂性质、电压和推速对表面形貌的影响;采用傅里叶变换红外光谱仪(FT-IR)、动态水分吸附分析仪(DVS)和差示扫描量热仪(DSC)研究优化工艺参数下制备的相变储湿纤维的组成结构、储湿调湿性能和相变调温性能。相变储湿纤维的优化工艺参数,即聚乙二醇800与丙酮的质量比为0.15、醋酸纤维素与丙酮的质量比为0.13、N,N-二甲基乙酰胺与丙酮的质量比为0.20、电压为20.0 kV、推速为0.40 mL/h。结果表明,优化工艺参数下制备的相变储湿纤维在相对湿度为40%~60%时,平衡含湿量为0.0412~0.2239 g/g;在相变温度为21.53~29.25℃时,相变潜热为44.64~49.45 J/g。     

Experimental study on the thermal storage performance and preparation of paraffin mixtures used in the phase change wall

In this paper, several admixtures including n-heptadecane, n-octadecane, n-eicosane, 46^# paraffin, 48^# paraffin and liquid paraffin are prepared with different mixed proportion, aiming for appropriate phase change materials used in the building envelope. The phase change temperatures and phase change latent heats of several kinds of paraffin mixtures were studied experimentally by differential scanning calorimeter (DSC). The experimental results showed that the phase change temperatures and latent heats of paraffin mixtures change with their composition. Paraffin mixtures in different mass proportions have a wider phase change temperature range and higher phase change latent heat. So the paraffin mixtures can be used in the different thermal storage fields by adjusting the mixed proportion. Several paraffin mixtures with appropriate phase change temperatures and higher phase change latent heats were given, and they can be used in the building wall to storage thermal. The results in this paper can provide references and basis for the application of phase change material in the wall.     

The thermal storage performance of mixtures consisting of liquid paraffin and fatty acids

The thermal storage performance of binary mixtures consisting of fatty acids and liquid paraffin (LP) was studied experimentally. The study is to look for the material with suitable phase transition temperature and high phase change latent heat. The phase transition temperatures of binary mixtures consisting of capric acid and other four kinds of fatty acid are between 20°C and 30°C, and the phase change latent heat is high. They are ideal phase change materials used in the wall. The binary mixtures consisting of stearic acid, palmitic acid, lauric acid (LA) and myristic acid have high phase transition temperatures, and they are not suitable to use in the wall. The phase transition temperatures of mixtures consisting of LP and LA are between 20°C and 30°C, and the phase change latent heat is high. They can be used in the wall. The thermal stability of fatty binary mixtures is good.     

High accuracy interface characterization of three phase material systems in three dimensions

Quantification of interface properties such as two phase boundary area and triple phase boundary length is important in the characterization of many material microstructures, in particular for solid oxide fuel cell electrodes. Three-dimensional images of these microstructures can be obtained by tomography schemes such as focused ion beam serial sectioning or micro-computed tomography. We present a high accuracy method of calculating two phase surface areas and triple phase length of triple phase systems from sub-voxel accuracy segmentations of constituent phases. The method performs a three phase polygonization of the interface boundaries which results in a non-manifold mesh of connected faces. We show how the triple phase boundaries can be extracted as connected curve loops without branches. The accuracy of the method is analyzed by calculations on geometrical primitives.     

Thermal energy storage properties of a capric acid/stearic acid binary system and a 48# paraffin/liquid paraffin binary system

In this paper, the phase change temperature, latent heat and thermal stability of a capric acid/stearic acid binary system and a 48# paraffin/liquid paraffin binary system were experimentally studied. The experimental results showed that the phase change temperature and phase change latent heat change with the content of the component. The phase change temperatures of binary mixtures change in a wide range, so they can be used in different fields by adjusting the mixing ratio. The phase change latent heat of fatty acid mixtures is higher than that of paraffin mixtures. The thermal stability of fatty acid mixtures is better than that of paraffin mixtures. The mixtures used in the phase change material wall or the phase change material floor as energy storage materials were given in the paper.     

Semicrystalline proton-conductive membranes with sulfonated amorphous phases

Proton-conductive membranes, exhibiting high chemical and thermomechanical resistance, have been obtained by s-PS films with the β crystalline phase and a sulfonated amorphous phase. These membranes can be obtained by a solid-state procedure on δ form films, which allows an easy and uniform sulfonation of the phenyl rings of the amorphous phase and preserves the crystalline phase, followed by suitable thermal treatments leading to the δ → β crystal-to-crystal transition. The high degree of sulfonation of the amorphous phase makes this phase highly hydrophilic and proton conductive while the presence of the high melting and thermodynamically stable β phase assures high chemical and thermomechanical stability.