脂肪酸复合相变材料的制备及其在日光温室中的应用

发布时间：2018-01-10 10:07

本文关键词：脂肪酸复合相变材料的制备及其在日光温室中的应用　出处：《西北农林科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：日光温室是我国重要的农业生产设施,在我国的农业发展中有着极其重要的作用。然而在实际的生产过程中,尤其在北方寒冷地区,日光温室常常难以确保作物安全越冬,还需要消耗能源对温室进行加热来提高最低温度,因而就增加了生产运行的成本。近年来相变蓄热材料的研究,给节能日光温室的研究提供了新的思路。将相变储能技术应用于温室,将在降低能源消耗,改善温室热环境,优化日光温室墙体结构等方面,有着非常重要的意义。本研究的主要内容如下：(1)开发了适用于日光温室的三元脂肪酸定形复合相变材料：月桂酸-肉豆蔻酸-癸酸／膨胀石墨,并对其性能进行了测试。研究结果表明：该定形复合相变材料的相变温度为21.82℃,相变潜热为121.5J/g。膨胀石墨在定形复合相变材料中所占质量分数为8%。在表面张力和毛细作用下,相变材料被固定到膨胀石墨的微观孔隙中,在融化情况下也没有材料泄露现象发生。经1000次加速冷热循环之后,定形复合相变材料熔点变化了-0.22℃,潜热变化了-2.3%,变化幅度极小,表现出了良好的热稳定性和化学稳定性。定形复合材料的导热系数为1.79W/(m-K),相比于纯相变材料提高了近6.5倍,极大地改善了脂肪酸材料导热性能差的问题。(2)将定形复合相变材料与菱镁墙板结合,设计出一种相变蓄热墙板,并进行了应用效果分析。通过选取典型天气条件下室内的气温、20cm深处地温、墙体温度、墙体热流等环境数据进行分析对比,所得主要结论如下：晴天天气条件下,装有相变蓄热墙板的温室白天的最高气温平均比对照低0.9℃,最大可低3.4℃,夜间最低气温比对照温室要高出2.3℃,最大可高2.9℃；20cm深处的地温比对照温室高0.8～1.1℃；白天相变蓄热墙板的累计吸热量为6.18MJ/m2,比对照砖墙高2.05MJ/m2；夜晚相变蓄热墙板的累计放热量为2.24MJ/m2,比对照砖墙高101MJ/m2。在阴天天气条件下,相变蓄热温室的气温比对照温室要高出1.1～1.7℃；20cm深处的地温比对照高0.9-1℃；白天相变蓄热墙板累计吸热量0.79 MJ/m2,高于对照砖墙0.14 MJ/m2；夜间相变蓄热墙板夜间累计放热量为0.53 MJ/m2,比对照墙体高出03MJ/m2。相变蓄热墙板的应用明显地提高了日光温室的蓄热量,降低白天温室内的过高的温度,提升夜间室内的最低温度,对室内热量起到了“削峰填谷”的调节作用。该研究为进一步改善温室热环境,降低温室内能源消耗,提供了一定的参考价值。
[Abstract]:Solar greenhouse is an important agricultural production facilities in China, plays an important role in the development of agriculture in our country. However, in the actual production process, especially in the northern cold area, the greenhouse is often difficult to ensure the safety of crops in winter, also need to consume energy to heat the greenhouse to raise the minimum temperature, thus increasing the production cost of running. In recent years the research on phase change materials, provides a new way for the research of energy saving solar greenhouse. The phase change energy storage technology in greenhouse, will reduce energy consumption, improve the greenhouse thermal environment, optimize the structure of wall in solar greenhouse, has a very important significance. The main contents of this the research is as follows: (1) three yuan of fatty acid composite phase change material developed for greenhouse: lauric acid and myristic acid and capric acid / expanded graphite, and its properties were tested. The results show that the phase transition temperature of composite phase change material is 21.82 DEG C, latent heat for 121.5J/g. graphite in composite phase change material in the mass fraction of 8%. in surface tension and capillary effect, the phase change material is fixed to the micro pores of expanded graphite, in case there is no leakage of material melting phenomenon 1000. After accelerated thermal cycling. The composite phase change material melting point changes -0.22 C, heat change -2.3%, change amplitude is very small and showed good thermal stability and chemical stability. The thermal conductivity of composite materials for 1.79W/ (m-K), compared to the pure phase change materials increased nearly 6.5 times, greatly to improve the thermal conductivity of the fatty acid material is poor. (2) the combination of amorphous composite phase change material and magnesite wall, design a kind of phase change wallboard, and the application effect analysis. By choosing the indoor temperature under typical weather conditions, 20cm deep soil temperature, wall temperature, wall heat flux and environmental data were analyzed, the main conclusions are as follows: sunny weather conditions, the highest temperature with phase change wallboard greenhouse in average 0.9 lower than the control temperature, the maximum can be 3.4 lower than the control temperature, the minimum temperature at night the greenhouse is up to 2.3 degrees, the maximum temperature 2.9 DEG C higher than the control; 20cm inside the greenhouse is higher 0.8 ~ 1.1 DEG C; the cumulative amount of heat during the day phase change wallboard is 6.18MJ/m2 than the control 2.05MJ/m2 high brick wall; phase change thermal storage wall night accumulated heat release is 2.24MJ/m2, than the control brick high 101MJ/m2. in cloudy weather conditions under greenhouse temperature phase change than the control of greenhouse is up to 1.1 to 1.7 DEG C; 20cm deep temperature higher than the control at 0.9-1 during the day; phase change wallboard cumulative heat absorption of 0.79 MJ/m2 high. In the control of brick 0.14 MJ/m2; the night phase change wallboard night accumulated heat release is 0.53 MJ/m2, higher than the control wall using 03MJ/m2. PCM Wallboard can obviously improve the heat storage of solar greenhouse, reducing daytime greenhouse temperature, raising the minimum temperature during nighttime, the adjustment function of "peak" the indoor heat. The research to further improve the greenhouse thermal environment, reduce greenhouse energy consumption, to provide a certain reference value.

【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB34

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