【作者】 袁芳；

【导师】 李友荣；

【作者基本信息】 重庆大学 ， 动力工程及工程热物理， 2024， 硕士

【摘要】 吸附式空气取水技术具有取水能耗低、取水效率高、能利用可再生清洁能源、适用地区广等优点,是一种非常有潜力的大气取水方式,有望解决淡水资源短缺问题。目前国内外学者开发的吸附式取水系统大都为间歇式取水系统,一天只能进行一个吸附/解吸循环,日取水量不高;有关吸附式取水系统的研究多为实验研究,缺乏对系统中各部件热力过程和影响参数的分析。本文以我国西北地区气象条件为研究背景,以65 kg/day为目标取水量,构建了一个一日内可进行多个取水循环的太阳能储能-连续吸附式空气取水系统;建立了吸附床和真空集热管的物理数学模型,分析了运行参数和结构参数对其热力学性能的影响;最后分析了系统整体性能并进行了改进。主要研究内容和结论如下:(1)构建了一个太阳能储能-连续循环吸附式空气取水系统,该系统采用完全相同的两床并联运行,连续交替进行吸附/解吸循环;利用填充相变材料的真空集热管作为空气加热器,相变材料在白天储存太阳能以提高太阳能利用率。(2)建立了吸附床的物理数学模型,利用Matlab软件编写数值程序,对吸附床的传热传质过程进行了模拟,分析了吸附/解吸过程中运行参数对循环性能的影响。结果表明,环境温度在25～30℃范围内吸附床有较好的性能;环境相对湿度越高,吸附床性能越好;再生空气温度为90℃时,吸附床性能最佳。(3)建立了集成相变材料的真空集热管物理数学模型,通过ANSYS Fluent软件模拟了集热管运行24 h内的传热过程,分析了套管内管管径、空气流量以及相变材料对集热管集热性能的影响。结果表明,套管内管管径为16 mm时集热管集热性能最好;空气流量越大,集热效率越高,但阻力损失也随之增大;真空管集成复合相变材料10%六水硝酸镁+90%六水氯化镁时集热性能最好。(4)对系统整体性能进行了分析和改进,系统在兰州地区7.17日气象条件下运行时,增设聚光反射器后系统理论日取水量最高可达66.4 kg,此时单位质量吸附剂取水量SMP为2.26 kg/kg/day,较改进前增加了1.25 kg/kg/day;单位面积太阳能集热器理论取水量SWP最大值为1.8 kg/day/m~2,较改进前提升了12.5%。系统在不同流量下的最佳取水性能随冷凝温度的升高先上升、后下降,在40℃时系统取水性能最佳,故冷凝温度并不是越低越好,应根据具体运行情况与解吸温度进行匹配。更多还原

【Abstract】 The adsorption air water extraction technology has the advantages of low energy consumption,high water extraction efficiency,the utilization of renewable clean energy,and wide applicability.It is a very promising atmospheric water extraction method,which is expected to solve the problem of freshwater resource shortage.At present,most of the adsorption air water extraction systems developed by domestic and foreign scholars are intermittent water extraction systems,which can only perform one adsorption/desorption cycle per day,and the daily water extraction volume is not high.In addition,research on adsorption water extraction systems is mostly experimental,lacking specific analysis of the thermal processes and influencing parameters of each component in the system.This thesis takes the meteorological conditions in the northwest region of China as the research background,with a target water extraction amount of 65 kg/day,and constructs a solar energy storage-continuous adsorption air water extraction system that can carry out multiple water extraction cycles within a day.We established physical and mathematical models for adsorption beds and vacuum heat collectors,and analyzed the effects of operating and structural parameters on their thermodynamic performance.Finally,the overall performance of the system was analyzed and improved.The main research content and conclusions are as follows,(1)A solar energy storage-continuous cycle adsorption air water extraction system has been constructed,in which two beds are parallel and identical,continuously alternating adsorption/desorption cycles.Vacuum heat collection tubes filled with phase change materials are used as air heaters,which store solar energy during the day to improve solar energy utilization efficiency.(2)A physical and mathematical model of the adsorption bed was established,and a numerical program was written using Matlab to simulate the heat and mass transfer process of the adsorption bed.The influence of operating parameters on the cycling performance during the adsorption/desorption process was analyzed.The results indicate that the adsorption bed has good performance in the ambient temperature range of(25-30)℃.The higher the relative humidity of the environment,the better the performance of the adsorption bed.When the temperature of the regenerated air is 90℃,the adsorption bed has the best performance.(3)A physical and mathematical model of a vacuum heat collector tube with integrated phase change materials was established.The heat transfer process of the heat collector tube during 24 hours of operation was simulated using ANSYS Fluent software.The effects of the tube diameter,air flow rate,and phase change materials on the heat collection performance of the heat collector tube were analyzed.The results indicate that the collector tube has the best heat collection performance when the diameter of the inner tube of the casing is 16mm.The larger the air flow rate,the higher the heat collection efficiency,but the resistance loss also increases accordingly.The vacuum tube has the best heat collection performance when filled with a composite phase change material of10%magnesium nitrate hexahydrate+90%magnesium chloride hexahydrate.(4)Preliminary analysis and improvement analysis were conducted on the overall performance of the system.When the system operates under meteorological conditions in Lanzhou on July 17th,the theoretical daily water extraction capacity of the system can reach up to 66.4 kg after adding a spotlight reflector.At this time,the SMP of the unit mass adsorbent water extraction capacity is 2.26 kg/kg/day,which is an increase of 1.25kg/kg/day compared to before the improvement.The maximum theoretical water extraction capacity SWP of a unit area solar collector is 1.8 kg/day/m~2,which is 12.5%higher than before improvement.The optimal water extraction performance of the system at different flow rates shows a trend of first increasing and then decreasing with the increase of condensation temperature.At T_c=40℃,the system has the best water extraction performance,so the condensation temperature is not necessarily lower than better.It should be matched with the desorption temperature according to specific operating conditions.更多还原