乳液冰浆蓄冷性能实验研究

发布时间：2018-02-28 12:22

  本文关键词： 蓄冷 冰浆 乳液 纳米粒子　出处：《苏州科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着我国社会和经济的发展,电力需求也日益增长,高能耗、能源分布不均和电网峰谷差等问题逐渐突显出来。蓄冷空调是一种可以充分利用低谷电的节能技术,是电力“移峰填谷”和解决尖峰电力不足的有效方法。目前水和冰是应用最广泛的蓄冷介质,其中水蓄冷是利用显热蓄冷,蓄冷密度低,但具有较好的流动性;冰蓄冷利用潜热蓄冷,蓄冷密度大但无法直接输送冷量。冰浆是冰晶粒子均匀分布的固液两相流体,同时兼顾了水蓄冷的流动性和冰蓄冷蓄冷密度大的优点。冰浆以其良好的热物理性质,在作为一种新型无污染的蓄冷及载冷介质等方面具有重大的研究价值和广阔的应用前景。在冰浆制取、运输和储存过程中,克服冰堵和提高流动性是其推广应用的关键,也是当前冰蓄冷技术的研究热点。本文在油-水中添加少量添加剂(硅烷偶联剂、表面活性剂+乙醇)配制了两组实验体系,通过搅拌降温制备了乳液冰浆,得到乳液的冰点和过冷度,观察了冰晶粘附壁面情况、冰粒大小和冰浆流动性。采用混合量热法研究表面活性剂和乙醇对冰浆含冰率的影响,通过旋转粘度计、显微镜分别测定表观粘度和冰粒粒径,表征乳液冰浆的蓄冷性能和流动性能。实验结果表明表面活性剂Span80、T80和油酸阻碍了冰晶的团聚,提高了冰晶的分散均匀性,但不影响冰浆含冰率。乙醇的添加,降低了冰浆的冰点和含冰率,增大了过冷度,但抑制了壁面冰层的出现。冰浆表观粘度和冰粒粒径都随着含冰率的增加而增加。当恒温空气浴为-8.5℃,结晶时间为90min时,添加剂成分为E2.6(1.0wt%Span80+3.0wt%ET)、E2.17(2.0wt%T80+4.0wt%ET)、E2.23(0.5wt%油酸+3.0wt%ET)冰浆的冰点分别为-1.8℃、-2.3℃和-1.8℃,过冷度分别为4.1℃、4.5℃和4.2℃,含冰率分别为31.6%、32.2%、32.2%,表观粘度分别为47.0 mPa·s、32.0 mPa·s、25.5mPa·s,粒径分别为1.34mm、1.60mm、2.00mm,形成的冰浆含冰率高,流动阻力小,冰晶不粘附壁面,是代替硅烷偶联剂作为冰浆添加剂的配比方案。为了减小冰浆的过冷度,本文采用超声震荡方法将纳米CuO粒子分散到乳液冰浆中,通过重力沉降和分光度来表征纳米流体的分散稳定性,筛选出分散效果好的实验体系。采用混合量热法测试了含有纳米CuO乳液冰浆的含冰率,并获得了冰浆形成的相变温度、过冷度,采用T-history方法计算出其比热容和导热系数,研究了纳米CuO粒子质量分数对比热容、导热系数、相变温度、过冷度和含冰率的影响。实验结果表明纳米CuO的加入,对冰浆相变温度的影响不大,降低了冰浆的比热容和过冷度,提高了冰浆的导热系数和含冰率,有效地克服了乙醇的不利影响,起到了促晶成核、增强传热的作用,提高了冰浆的蓄冷性能。
[Abstract]:With the development of our country's society and economy, the demand for electric power is increasing day by day. The problems of high energy consumption, uneven distribution of energy and difference between peak and valley of power grid are becoming more and more obvious. Storage air conditioning is a kind of energy saving technology which can make full use of low power. At present, water and ice are the most widely used cold storage medium, in which water storage is the use of sensible heat storage, the cold storage density is low, but it has good fluidity. Ice storage is a solid-liquid two-phase fluid with uniform distribution of ice crystal particles. At the same time, the fluidity of water storage and the advantages of high density of ice storage are taken into account. It has great research value and broad application prospect as a new kind of non-pollution cold storage and carrier cold medium. In the process of ice slurry manufacture, transportation and storage, overcoming ice blocking and improving fluidity are the key to its popularization and application. In this paper, a small amount of additives (silane coupling agent, surfactant ethanol) were added to the oil and water to prepare two groups of experimental systems, and the emulsion ice slurry was prepared by stirring and cooling down. The freezing point and undercooling degree of the emulsion were obtained. The ice crystal adhesion to the wall, the ice particle size and the ice slurry fluidity were observed. The effects of surfactant and ethanol on the ice content of ice slurry were studied by mixing calorimetry. The apparent viscosity and ice particle size were measured by microscope to characterize the cold storage property and fluidity of ice slurry. The experimental results showed that the surface active agent Span80 T80 and oleic acid hindered the aggregation of ice crystals and improved the dispersion uniformity of ice crystals. But it has no effect on the ice content of the ice slurry. The addition of ethanol reduces the freezing point and ice content of the ice slurry and increases the degree of undercooling. But the appearance of wall ice layer was inhibited. The apparent viscosity and particle size of ice slurry increased with the increase of ice content. When the temperature of air bath was -8.5 鈩，

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