太阳能相变蓄能通风系统实验研究

针对太阳能通风的不稳定性和不可控性,提供一种利用太阳能作为热源,相变蓄热材料在日间进行蓄热,夜间利用储存热量热压通风的新型系统,使建筑物达到理想的通风效果。通过分别对相变温度为63℃、44℃的相变蓄热材料进行通风实验,得到不同相变温度下系统夜间通风量变化特性。结果表明,采用相变温度分别为63℃、44℃的相变蓄热材料棕榈酸和月桂酸,太阳能通风系统在夜间通风10 h累计通风量分别为806.6 m3、615.4 m3,单位面积水平集热面通风量分别为53.8 m3/h、41 m3/h。使用棕榈酸的通风系统效果要优于使用月桂酸。提出的太阳能通风屋顶结合相变蓄热系统能有效的强化建筑物夜间自然通风,改善建筑室内热环境,减少空调用能。     

太阳能蓄能通风系统理论模型

建立一个太阳能蓄能通风系统的理论模型,以计算该系统白天蓄热量和夜间通风量.以昆明市气象参数为依据,分析了采用相变材料的相变温度分别为38、44、50、63℃时,该系统通风量与烟囱倾角的变化关系.计算结果表明,对于不同相变材料,无论在何倾角下,他们的蓄热量大小趋势都是一致的,即相变温度越高,蓄热量越小.综合考虑通风量和通风时长2种因素,系统最佳倾角应该为45°,而最佳相变材料应为38℃十四烷酰.     

太阳能相变蓄热加热输送原油系统

根据太阳能的特点和原油加热输送过程的工艺条件,设计了一套太阳能相变蓄热加热原油系统,研制开发了一种适用于太阳能加热的相变蓄热装置,对蓄热装置放热过程中的部分热工参数进行了测量。通过分析可知,该系统利用太阳能加热原油,相变蓄热装置的传热性能较好,装置在55~85℃范围内所蓄热量是同体积水作蓄热材料的蓄热装置所蓄热量的3.5倍,设备具有体积小、蓄热量大、放热温度均匀、便于控制加热温度等特点。     

膨胀石墨/石蜡复合相变蓄热材料的制备及性能研究

以石蜡作为相变蓄热材料的基本材料,利用膨胀石墨的高吸附性和高导热性提高相变材料的传热性能,制备出不同配比的中低温相变蓄热材料,利用DSC测试出各组复合相变蓄热材料的热物性参数.研究结果表明:膨胀石墨含量不宜过多,应该小于5％;添加的膨胀石墨对石蜡相变点和焓变的影响很小.     

膨胀石墨/石蜡复合相变蓄热材料的制备及性能研究

以石蜡作为相变蓄热材料的基本材料,利用膨胀石墨的高吸附性和高导热性提高相变材料的传热性能,制备出不同配比的中低温相变蓄热材料,利用DSC测试出各组复合相变蓄热材料的热物性参数.研究结果表明:膨胀石墨含量不宜过多,应该小于5%;添加的膨胀石墨对石蜡相变点和焓变的影响很小.     

聚乙二醇/氧化石墨烯相变储能材料研究

以氧化石墨烯(GO)为载体材料和导热增强相,聚乙二醇(PEG)为相变材料,制备得到了聚乙二醇/氧化石墨烯(PEG/GO)复合相变储能材料。对产物进行FTIR、SEM、DSC等测试表征,并分析了GO的添加量对制备得到的PEG/GO复合相变储能材料的相变稳定性和导热性的影响。实验结果表明,GO的高比表面积和二维片层结构有利于提高其对PEG的吸附效果,当GO含量为15%时,PEG/GO复合相变材料在高于PEG熔融温度时具有良好的形状稳定性,其热导率与纯PEG相比提高了近6倍,同时复合材料仍具有较高的相变焓。     

Role of Composite Phase Change Material on the Thermal Performance of a Latent Heat Storage System: Experimental Investigation

复合相变材料对潜热储能系统中热性能作用的实验研究

Jasim Abdulateef¹, Ahmed F. Hasan^2*,Mustafa S. Mahdi²

（1. 迪亚拉大学 机械工程系,巴古拜 32001,伊拉克;2.迪亚拉大学 化学工程系,巴古拜 32001,伊拉克）

摘要：

石蜡是可用于潜热储能系统单元（LHSU）的理想的相变材料（PCM）。这种潜热储能单元的使用因相变材料导热性差而受到限制。本文采用铝和相变材料制成的金属泡沫生产复合相变材料,以此作为相变材料-潜热储能单元中的导热材料,并使用水作为传热流体（HTF）。通过实验,评估了使用纯相变材料和复合相变材料的潜热储能单元的传热特性。研究包括熔化和凝固过程中相变材料的时变可视化。此外,热存储室内放置一个热电偶网络,记录每个过程的温度分布。结果表明,复合相变材料-潜热储能单元在熔化和凝固过程中均表现出较好的性能。由于金属泡沫的作用,复合相变材料-潜热储能单元的熔化时间比简单的相变材料-潜热储能单元快83%左右,凝固时间减少85%左右。

关键词：相变材料;金属泡沫;潜热;复合相变材料

     

蓄能型太阳能热泵系统中复合材料蓄热过程研究

设计了一种分季节蓄能型太阳能热泵热水系统,集太阳能集热容器、相变储能容器、热管于一体,利用Fluent软件对蓄能型太阳能集热器开展了数值模拟,使用Solidification/Melting和VOF模型模拟癸酸/62#石蜡复合相变材料蓄热过程,并采用Boussinesq近似法考虑了自然对流的影响. 结果表明,在集热器内只充灌单一相变材料不能满足不同季节蓄能型热泵系统的供热水需求. 由癸酸和62#石蜡组成的复合相变材料在蓄能过程中出现了两个相变温度,分别在32.66 ℃和59.45 ℃,可以满足本系统不同季节的蓄热需求. 蓄热过程中,由于癸酸和62#石蜡本身密度差以及浮升力的影响,真空管纵向截面出现了温度分层现象. 结果可为复合相变储能材料的推广应用提供可靠的理论依据.     

低熔点石蜡微胶囊保温砂浆的热性能

以低熔点石蜡微胶囊为相变材料,制备石蜡微胶囊保温砂浆。测试了保温砂浆的热焓、相变温度、导热系数和相变蓄热性能。结果表明：石蜡微胶囊保温砂浆具有良好的蓄热、调温功能和较长的热循环寿命,砂浆体系的相变温度为33℃,相变潜热13.42J/g;随着偶联剂和粘结剂掺量的增加,保温砂浆的导热系数呈下降趋势;随着石蜡微胶囊掺量增加,保温砂浆的导热系数先减后增;与空白试件相比较,相变蓄热砂浆的升降温速率明显要滞后,呈现出较好的蓄热、调温性能。     

一种新型高温复合相变蓄热材料的制备

采用粉末烧结工艺将相变材料Na2CO3和基体材料MgO进行复合,制成一种新型高温复合相变蓄热材料.通过XRD和TG?DTA分析,结果表明:由Na2CO3/MgO构成的复合相变蓄热材料具有良好的化学相容性,在845℃时出现吸热峰.通过对其蓄热密度的计算可知:制备成的蓄热材料具有蓄热密度高的特点,能够实现高温蓄热.     

In-Situ Preparation and thermal shock resistance of mullite-cordierite heat tube material for solar thermal power

In order to improve the thermal shock resistance of solar thermal heat transfer tube material, the mullite-cordierite composite ceramic as solar thermal heat transfer tube material were fabricated by pressureless sintering using α-Al2O3 , Suzhou kaolin, talc, and feldspar as starting materials. The important parameter for solar thermal transfer tube such as water absorption (Wa ), bulk density (Db ), and the mechanical properties were investigated. The phase composition and microstructure of the composite ceramics were analyzed by XRD and SEM. The experimental results show that the B3 sintered at 1 300 ℃ and holding for 3 h has an optimum thermal shock resistance. The bending strength loss rate of B3 is only 2% at 1 100℃ by air quenching-strength test and the sample can endure 30 times thermal shock cycling, and the water absorption, the bulk density and the bending strength are 0.32%, 2.58 g·cm-3 , and 125.59 MPa respectively. The XRD analysis indicated that the phase compositions of the sample were mullite, cordierite, corundum, and spinel. The SEM images illustrate that the cordierite is prismatic grain and the mullite is nano rod, showing a good thermal shock resistance for composite ceramics as potential solar thermal power material.     

CaCl2·6H2O/EG复合相变材料的制备与性能研究

为了改善六水氯化钙的蓄放热性能,以六水氯化钙为相变材料（PCM）、膨胀石墨（EG）为载体、六水氯化锶为成核剂,采用物理吸附法制备六水氯化钙/膨胀石墨复合相变材料,研究复合相变材料的热物理特性. 采用步冷曲线法,研究复合相变材料的过冷度、蓄/放热性能和热循环稳定性;采用扫描电镜、差示扫描量热法、热流计导热仪,对复合相变材料的显微形貌、相变潜热、相变温度、比热容和导热系数进行测定. 结果表明：在六水氯化钙中添加质量分数为10%的膨胀石墨和质量分数为2%的六水氯化锶,复合相变材料的相变潜热为151.6 J/g,导热系数提升至3.328 W/(m·K),过冷度保持在2 °C以内. 相变材料的导热系数及过冷度得到显著改善.     

不同方法制备LiNO3NaCl/EG复合相变储热材料的热物性分析

选用LiNO_3-NaCl(87:13)二元混合相变熔盐作为相变材料,高导热系数的膨胀石墨作为复合基载材料,分别采用机械混合熔融法和超声波粉碎法制备了LiNO_3-NaCl/EG复合相变材料。通过热重及同步热分析仪对复合材料的热物性进行了测试分析。进而比较了不同制备方法的优缺点,并通过相变理论对材料的相关物性进行了分析。     

膨润土/月桂酸/鳞片石墨定型储热材料的制备及性能

采用天然膨润土和月桂酸分别作为支撑基体和相变材料,通过真空浸渍法合成复合相变储热材料。结果表明,添加鳞片石墨不仅提高复合相变储热材料的导热特性,而且阻止相变材料从复合相变材料中泄露。制备的复合相变储热材料经历200次热循环实验后,仍具有较好的可靠性,具备在热能存储系统中应用的较大潜力。     

Preparation and characterization of CA-MA eutectic/silicon dioxide nanoscale composite phase change material from water glass via sol-gel method

This work mainly involved the preparation of a nano-scale form-stable phase change material(PCM) consisting of capric and myristic acid(CA-MA) binary eutectic acting as thermal absorbing material and nano silicon dioxide(nano-SiO_2) serving as the supporting material. Industrial water glass for preparation of the nano silicon dioxide matrix and CA-MA eutectic mixture were compounded by single-step sol-gel method with the silane coupling agent. The morphology, chemical characterization and form stability property of the composite PCM were investigated by transmission electron microscopy(TEM), scanning electron microscopy(SEM), Fourier-transform infrared(FT-IR) spectroscopy and polarizing microscopy(POM). It was indicated that the average diameter of the composite PCM particle ranged from 30-100 nm. The CA-MA eutectic was immobilized in the network pores constructed by the Si-O bonds so that the composite PCM was allowed no liquid leakage above the melting temperature of the CA-MA eutectic. Differential scanning calorimetry(DSC) and thermogravimetric analysis(TGA) measurement were conducted to investigate the thermal properties and stability of the composite PCM. From the measurement results, the mass fraction of the CA-MA eutectic in the composite PCM was about 40%. The phase change temperature and latent heat of the composite were determined to be 21.15 ℃ and 55.67 J/g, respectively. Meanwhile, thermal conductivity of the composite was measured to be 0.208 W·m~(-1)·K~(-1) by using the transient hot-wire method. The composite PCM was able to maintain the surrounding temperature close to its phase change temperature and behaved well in thermalregulated performance which was verified by the heat storage-release experiment. This kind of form-stable PCM was supposed to complete thermal insulation even temperature regulation by the dual effect of relatively low thermal conductivity and phase change thermal storage-release properties. So it can be formulated that the nanoscale CA-MA/SiO_2 composite PCM with the form-stable property, good thermal storage capacity and relatively low thermal conductivity can be applied for energy conservation as a kind of thermal functional material.     

夜间通风相变复合墙体动态传热模拟

为研究由相交混凝土复合墙体构造的房间在夜间通风下的热环境,利用焓法建立结合夜间通风的相变混凝土复合墙体动态传热和房间传热数学物理模型,模拟研究北京地区夏季和过渡季应用该相变复合墙体动态传热和室内热环境的时变特性.对该相变复合墙体传热的影响因素,如相变温度、相变层厚度、通风次数、通风时间以及相变层和绝热层的位置等进行优化...     

正交试验法研究定形复合相变材料的制备工艺

为制备适用于调温纺织品领域的定形相变材料,用溶胶-凝胶法制备了复合相变材料,其中定形材料为以正硅酸乙酯为前驱体通过溶胶-凝胶法制得的二氧化硅凝胶,以月桂酸/十六醇二元低共熔物为相变材料.采用正交试验法研究了溶胶-凝胶法制备复合相变材料的工艺条件.各因素影响复合相变材料的控温能力次序为:酯PCM比>酯水比>pH>反应温度...     

Effect of nano-ZrO2 on microstructure and thermal shock behaviour of Al2O3/SiC composite ceramics used in solar thermal power

The Al2O3-ZrO2(3Y)-SiC composite ceramics used in solar thermal power were prepared by micrometric Al2O3,nano-ZrO2 and SiC powders under the condition of pressureless sintering.The bulk density and bending strength of samples with 10vol% nano-ZrO2 sintered at 1480℃ were 3.222 g/cm3 and 160.4MPa,respectively.The bending strength of samples after 7 times thermal shock tests (quenching from 1000℃ to 25℃ in air medium) is 132.0MPa,loss rate of bending strength is only 17%.The effect of nano-ZrO2 content on the microstructure and performance of Al2O3-ZrO2(3Y)-SiC composite ceramic was investigated.The experimental results show that the bending strength of samples with above 10vol% nano-ZrO2 content has decreased,because the volume expansion resulting from t-ZrO2 to m-ZrO2 phase transformation is excessive;Adding proper nano-ZrO2 would be contributed to improve the thermal shock resistance of the composite ceramics.The Al2O3-ZrO2(3Y)-SiC composite ceramic has promising potential application in solar thermal power.