磁场对HCFC-141b制冷剂水合物生成及分解过程的影响研究

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	磁场对HCFC-141b制冷剂水合物生成及分解过程的影响研究
其他题名	EFFECTS OF MAGNETIC FIELDS ON HCFC-141b REFRIGERANT GAS HYDRATE FORMATION AND DECOMPOSITION PROCESS
	刘勇
导师	樊栓狮
	2003
学位授予单位	中国科学院广州能源研究所
学位授予地点	中国科学院广州能源研究所
学位名称	硕士
学位专业	热能工程
关键词	气体水合物磁场引导时间水合率分解
摘要	气体水合物是指气体或易挥发性液体在一定温度下（一般高于冰点温度）与水结合而成的包络状晶体，作为大分子的气体或液体被水分子环绕，中间通过范德华力而形成的。气体水合物通常包括制冷剂气体水合物、天然气气体水合物和CO2气体水合物。制冷剂气体水合物可以在。℃以上结晶，生成的晶体类似于普通的冰，所以又称“暖冰”。由于制冷剂气体水合物的相平衡温度是在5-12℃之间，同时结晶时释放出相变潜热与冰的融解潜热相当，可以用来替代冰作为蓄冷空调系统中的储能介质，且其工作性能和适用性都大大优于冰。为发展经济的储能介质，应该考虑使用低压环保制冷介质作为蓄冷空调的储能介质。但是低压介质中，比如Rn和R141b等在水合物生成过程中都不活泼，相界面处扩散速度很慢，相与相之间难于充分混合，反应的诱导期长，过冷度大，生长速度也很慢，即使加表面活性剂和晶种后也改善不多。因此制冷剂水合物作为相变储能介质的实际应用中，水合物的快速均匀生成是技术成功的关键，也是技术的难点。电场和磁场可以对许多晶体生成的相平衡条件和生长动力学产生显著影响。这些外场对气体水合物生成的作用目前还没有可靠的实验数据。Makogon圆指出静磁场会对天然气气体水合物的结构和密度发生作用，在场的影响下，天然气气体水合物的密度会变大，结构会更有规律。目前，磁场对制冷剂气体水合物生成及分解过程的影响还未见公开文献报道。本文通过实验发现通过铁丝短路不同直径组合的磁铁所形成的特殊磁场，会对HCFC-141b制冷剂气体水合物的生成及分解过程产生显著的影响。用可视化方法对磁场作用下水合物的生长形态进行了研究，发现磁场可以改变水合物的生长方向，扩大水合物的生长区域。磁场影响下水合物生成的引导时间显著缩短，生成质量显著增多，没有磁场时引导时间大约九小时，水合率大约 26％，在磁场作用下，引导时间缩短到最小4Omin左右，许多情况下水合率可以达到100％。研究了磁极、磁场强度、铁丝根数的变化对水合物生成的引导时间和水合率的影响，并初步获得了一些规律。发现磁场会影响HCFC-141b制冷剂气体水合物的分解过程，在磁场作用下，水合物的分解点升高大约近软左右。对磁场能够影响水合物的生成及分解过程机理进行了讨论。
其他摘要	Gas hydrate are crystalline compounds formed (usually above 0°C) by water, reacting with some gases or volatile liquids (hydrate former). Guest molecules, such as gas or volatile liquid molecules, are enclosed firmly inside the host cavities and act with water molecules in weak Van der Waals force. Gas hydrate usually includes natural gas hydrate, refrigerant gas hydrate and CO2 gas hydrate. Refrigerant hydrates can be formed above 0°C, and their crystallization is similar to ordinary ice, so it is also called "warm ice". Because the phase change temperature of the refrigerant gas hydrate is between 5 and 12°C and with a formation heat which is close to that of ice, it can be a substitute of cool storage medium for air-conditioning systems. The performance and applicability of the gas hydrate cool storage system can have a great superiority to that of the ice. To develop a cost-effective cool storage system for air-conditioning, a low-pressure gas hydrate cool storage medium should be employed. Unfortunately, those low-pressure refrigerants, such as Rll and HCFC-141b, are comparatively inactive in gas hydrate formation. In ordinary condition, guest species and water phases are scarcely mixed and the diffusion speed of different components through the interphase is very slow. Consequently, one has a very long induction time of reaction and a quite slow growth speed, even with surfactants and nucleate seeds added. Therefore, if refrigerant hydrates are employed as a medium of thermal energy storage t in engineering application, a rapid and uniform formation of gas hydrate will be the key for technical success. Electrical and magnetic fields may affect significantly the equilibrium formation conditions and growth kinetics of many crystallization process. Currently, there are no reliable experimental and theoretical data about the effect of these fields on gas hydrate formation. Makogon1561 indicated the effect of a stationary magnetic field on density and structure of hydrates. Denser hydrates with more regular structure may be formed under the influence of magnetic field. At present, there are no literatures about the effects of magnetic fields on refrigerant gas hydrate formation and decomposition processes. In this paper, the effects of a magnetic field on the formation process of HCFC-141b refrigerant gas hydrate are depicted experimentally. The visualization of the refrigerant gas hydrate formation was carried out and the morphology of the hydrate crystallization process in the applied magnetic field was studied. It is found that the orientation and growth region of gas hydrate are altered when subjected to different ways of the magnetic field; the induction time of hydrate crystallization can be shortened extremely under influence of the field: e.g. it can be shortened to 40min from 9h; the hydrate formation mass can be enhanced considerably; and the hydration rate can arrive at 100% in some instances. Meanwhile, the relations of induction time and hydration rate changed with magnetic pole and intensity and the number of iron wires are depicted. It is also found throughthe experiment that magnetic field can affect the HCFC-141b refrigerant gas hydrate decomposition process, and the decomposition temperature is elevated about Ik, comparing to that without magnetic field. The mechanism that magnetic field affects refrigerant gas hydrate formation and decomposition process is discussed.
页数	65
语种	中文
文献类型	学位论文
条目标识符	http://ir.giec.ac.cn/handle/344007/3857
专题	中国科学院广州能源研究所
推荐引用方式 GB/T 7714	刘勇. 磁场对HCFC-141b制冷剂水合物生成及分解过程的影响研究[D]. 中国科学院广州能源研究所. 中国科学院广州能源研究所,2003.

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