硅藻土基定形复合相变储能材料的制备与性能研究

发布时间：2018-06-22 01:02

  本文选题：相变材料 + 硅藻土　； 参考：《中国地质大学(北京)》2017年博士论文

【摘要】：建筑能耗约占社会总能耗的30%左右,把相变材料掺入到传统建筑材料中制成相变储能建筑材料,将太阳能以相变潜热的形式存储与释放,对降低建筑物能耗有重要的意义。本论文针对相变材料在实际应用中存在的两大致命问题:相变过程中因稳定性差造成的渗漏问题和相变材料导热率低的问题,提出利用我国丰富的硅藻土资源加工成高效定形复合相变储能材料,并在高导热速率等方面的应用上开展研究工作,实现建筑行业的节能降耗,为硅藻土的高附加值利用开辟新途径,具有明显的经济和社会效益。采用真空浸渍法,制备聚乙二醇(PEG)/硅藻土定形复合相变储能材料,首先对硅藻土进行碱处理,将硅藻土规则的孔雕饰成海绵状的孔。PEG均匀地浸渍到硅藻土的孔结构中,吸附量为70%,提高了46%,该数值为目前文献中的最高数值,且经过200次加热-冷却热循环,PEG不发生渗漏,具有优异的形态稳定性。PEG/硅藻土复合相变材料具有优异的储能密度,热稳定性和循环稳定性,活化能为1031.85 kJ/mol,高于纯PEG的活化能。采用水热还原法和溶液共混法分别在硅藻土的表面修饰纳米Ag颗粒和碳纳米管(SWCN),硅藻土的孔结构及比表面积均未发生明显变化,再浸渗液态PEG,获得高稳定性和高导热率的硅藻土基定形复合相变储能材料。当修饰粒径为3~10 nm的纳米Ag(7.2 wt%)颗粒时,复合相变材料的导热率为0.82 W/mK,较PEG本身提高了240%;当修饰SWCN(2 wt%)时,复合相变材料的导热率为0.87 W/mK,较PEG本身提高了260%。随着导热率的提高,PEG的熔化和凝固时间大大缩短了,过冷度降低,储热密度不发生变化。采用熔融共混法,制备LiNO_3/硅藻土和Na2SO_4/硅藻土中温和高温定形复合相变材料,LiNO_3和Na2SO_4均匀地浸渍到硅藻土的孔结构中,经过200次加热-冷却热循环,不发生液相渗漏,具有优异的形态稳定性。LiNO_3/硅藻土和Na2SO_4/硅藻土的工作温度分别为240~255℃和887.61~877.61℃,具有优异的储能密度,热稳定性和循环稳定性。分别以油页岩灰渣和正硅酸乙酯为原料,采用溶胶-凝胶法制备PEG/SiO_2低温和Na2SO_4/SiO_2高温定形复合相变材料。经过200次加热-冷却热循环,相变材料的化学性质与热物性能不发生变化,具有优异的热循环稳定性。这两种复合相变材料具有优异的储能密度,传热效率,热稳定性和形态稳定性。
[Abstract]:The building energy consumption accounts for about 30% of the total energy consumption of the society. It is of great significance to reduce the building energy consumption by adding the phase change material into the traditional building material to make the phase change energy storage building material and store and release the solar energy in the form of phase change latent heat. In this paper, there are two fatal problems in the practical application of phase change materials: the leakage caused by poor stability and the low thermal conductivity of phase change materials. It is put forward that using the rich diatomite resources in our country to produce high efficiency amorphous composite phase change energy storage materials, and to carry out research work on the application of high thermal conductivity rate, so as to realize energy saving and consumption reduction in the construction industry. It opens up a new way for the utilization of high added value diatomite and has obvious economic and social benefits. Polyethylene glycol (PEG) / diatomite composite phase change energy storage materials were prepared by vacuum impregnation. Firstly, diatomite was treated with alkali, and the regular diatomite holes were carved into spongy holes. PEG was evenly impregnated into the pore structure of diatomite. The adsorption capacity is 70, an increase of 46 percent, which is the highest value in the current literature, and after 200 heating-cooling heat cycles, PEG does not leak, and has excellent morphological stability. PEG / diatomite composite phase change material has excellent energy storage density. The activation energy is 1031.85 KJ / mol, which is higher than that of pure PEG. The surface modification of Ag nanoparticles and carbon nanotubes (SWCN) on the surface of diatomite by hydrothermal reduction method and solution blending method respectively did not change the pore structure and specific surface area of diatomite. Diatomite based composite phase change energy storage materials with high stability and high thermal conductivity were obtained by re-infiltration of liquid PEG. The thermal conductivity of the composite phase change material was 0.82 W / mKand 240W / mKhigher than that of PEG when modified with nano-Ag (7.2 wt%) particle size of 3 ~ 10 nm, and the thermal conductivity of the composite PCM was 0.87 W / m ~ (k) higher than that of PEG when modified SWCN (2 wt%), the thermal conductivity of composite phase change material was 0.87 W / m ~ (k), which was 260W / m ~ (-1) higher than that of PEG itself when modified SWCN (2 wt%). With the increase of thermal conductivity, the melting time and solidification time of PEG are greatly shortened, the supercooling degree is decreased, and the heat storage density does not change. LiNO3 / diatomite and Na _ 2SO _ 4 / diatomite were prepared by melt blending method. The mild high-temperature setting composite phase change materials LiNO3 and Na _ 2SO _ 4 were uniformly impregnated into the pore structure of diatomite. After 200 heating and cooling heat cycles, no liquid phase leakage occurred. The working temperatures of LiNO3 / diatomite and Na _ 2SO _ 4 / diatomite are 240 鈩，

本文编号：2050832