二水草酸相变储能材料的耐受性研究

发布时间：2018-04-20 11:31

本文选题：相变储能材料 + 二水草酸　；参考：《中国科学院大学(中国科学院青海盐湖研究所)》2017年硕士论文

【摘要】：随着人类生活的不断发展,化石燃料的大规模使用致使环境日渐恶化。相变储能材料能够实现热能的时空转换,提高能源使用率,可达到节约能源和保护环境的目的。二元羧酸是一类非常重要的中温相变储能材料。其中,二水草酸以其超高的相变潜热、低廉的成本优势,在储热领域有非常大的应用潜力,可广泛应用于太阳能储热系统、热泵和工业余热回收等领域。但是二水草酸的耐受性问题限制了其应用:首先,二水草酸在相变过程中易泄漏,多次热循环后其热物性质衰减严重;其次,二水草酸熔化时的体积膨胀以及对容器材料的腐蚀使得封装容器容易受到破坏,这些都阻碍了二水草酸作为相变储能材料的长期使用。因此改善二水草酸的循环稳定性,选择合适的封装容器材料成为推进其应用的关键。本论文以二水草酸为相变储能材料主体,采用不同实验手段对其进行加速热循环实验,通过差示扫描量热仪(DSC)、X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)等手段对其进行表征,分析其热物性质衰减的原因;根据衰减原因采取措施改善其循环稳定性;并进一步针对其酸性特征,对常见的金属及合金进行全浸腐蚀实验,筛选出合适的耐腐蚀的容器材料,研究结果表明:(1)通过对比二水草酸加速热循环前后的测试结果,得出其在熔化过程中会产生大量水蒸气,使体系内部压力增大,易产生泄漏。体系的密闭性好坏对二水草酸的循环稳定性影响非常大。寻找合适的材料与二水草酸复合降低其熔点,减少水蒸气的产生;制备二水草酸定型复合材料,抑制其在熔化过程中的泄漏,是改善二水草酸循环稳定性的两种途径。(2)通过筛选大量的有机、无机材料,最终选定氯化钠(NaCl)为合适的添加剂,9 wt%NaCl可使二水草酸的熔点从101.2°C降低至88.7°C,相变潜热依旧保持在320 J/g以上,100次热循环后熔化潜热衰减4.7%,循环稳定性得到大幅度提高。此外,实验发现聚乙二醇(PEG)的添加虽然未能降低二水草酸的熔点,但其作为稳定剂也一定程度上改善了二水草酸的循环稳定性,其中2.5 wt%PEG 6000效果最好。(3)依据多孔吸附法原理,实验采用多孔膨胀石墨对二水草酸+9 wt%NaCl复合相变储能材料进行物理吸附,制备了二水草酸多孔基体复合相变储能材料,并采用扫描电子显微镜(SEM),DSC等手段对其进行表征测试。泄漏测试与SEM分析结果表明:6 wt%的膨胀石墨能够完全将二水草酸+9 wt%NaCl复合相变储能材料吸附到其孔隙内部;DSC循环测试结果表明二水草酸多孔基体复合相变储能材料100次循环后熔化潜热仅衰减1.7%,二水草酸的循环稳定性得到了进一步改善。(4)针对二水草酸较强的酸性,本论文选用八种常见的耐腐蚀金属及合金,通过全浸腐蚀实验来测定其在二水草酸多孔基体复合相变储能材料中的抗腐蚀性。结果表明在常见金属及合金中,紫铜的腐蚀速率较低且价格低廉、易加工、导热性好,所以适合用做二水草酸多孔基体复合相变储能材料的封装材料。
[Abstract]:With the continuous development of human life, the large-scale use of fossil fuels has worsened the environment. Phase change energy storage materials can achieve time and space conversion of heat energy, increase the utilization of energy, and achieve the purpose of saving energy and protecting the environment. Two carboxylic acid is a very important kind of medium temperature phase change energy storage material. Among them, two oxalic acid is over the super energy. High phase transformation latent heat, low cost advantage, has great potential in the field of heat storage, and can be widely used in solar energy storage system, heat pump and industrial waste heat recovery. But the tolerance of two oxalic acid limits its application: first, two oxalic acid is easy to leak in the phase change process, and after many hot cycles, its thermal properties decline Secondly, the volume expansion of two water oxalic acid and the corrosion of the container material make the packaging containers vulnerable to damage, which all obstruct the long-term use of two oxalic acid as a phase change energy storage material. Therefore, it is the key to improve the cycle stability of two oxalic acid and choose suitable packaging container material to promote its application. In this paper, two oxalic acid was used as the main body of the phase change energy storage material, and the accelerated thermal cycling experiment was carried out by different experimental means. By means of differential scanning calorimeter (DSC), X ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and other means, the reasons for the attenuation of the properties of the thermal properties were analyzed, and measures were taken to improve the attenuation according to the attenuation reasons. For its cyclic stability, and further to its acidic characteristics, a total immersion corrosion experiment on common metals and alloys has been carried out to screen out suitable corrosion resistant container materials. The results show that: (1) a large amount of water vapor will be produced during the melting process by comparing the test results of two oxalic acid to accelerate the heat cycle. The tightness of the system has a great effect on the circulation stability of the two oxalic acid. Finding the suitable material to combine with two oxalic acid reduces the melting point and reduces the production of water vapor; the preparation of two water oxalic acid setting composite material and the inhibition of the leakage in the melting process can improve the stability of the two oxalic acid cycle. Two ways. (2) by selecting a large number of organic and inorganic materials, the final selection of sodium chloride (NaCl) is a suitable additive. 9 wt%NaCl can reduce the melting point of two water oxalic acid from 101.2 C to 88.7 C, the latent heat of phase change remains above 320 J/g, and the latent heat attenuation of the melting is 4.7% after 100 heat cycles and the stability of the cycle is greatly improved. In addition, real The addition of polyethylene glycol (PEG) can not reduce the melting point of two oxalic acid, but it also improves the cycle stability of two oxalic acid as a stabilizer, of which 2.5 wt%PEG 6000 has the best effect. (3) the porous expanded graphite is used for the composite phase change energy storage material of two aqueous oxalic acid +9 wt%NaCl based on the principle of porous adsorption method. A composite phase change energy storage material with two aqueous oxalic acid porous matrix was prepared by physical adsorption, and was characterized by scanning electron microscope (SEM) and DSC. The results of leakage test and SEM analysis showed that the 6 wt% +9 wt% NaCl composite phase change energy storage material could be absorbed into the pores completely; DSC was followed by DSC The loop test results show that the melt latent heat attenuates only 1.7% after 100 cycles of two aqueous oxalic acid porous matrix composite energy storage material, and the cyclic stability of two oxalic acid is further improved. (4) against the strong acidity of two oxalic acid, eight kinds of common corrosion resistant metals and alloys are selected in this paper, and they are measured in two by full immersion corrosion test. The results show that the corrosion rate of copper in common metals and alloys is low and low in corrosion rate, low in price, easy to be processed and good in thermal conductivity, so it is suitable to be used as a package material for the composite phase change energy storage material of two porous oxalic acid matrix.

【学位授予单位】：中国科学院大学(中国科学院青海盐湖研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB34

【参考文献】