湿度对室内颗粒物分布的影响

发布时间：2018-11-06 19:38

【摘要】：颗粒物作为室内空气中的主要污染物之一，其在室内的分布情况对室内空气品质至关重要。虽然目前国内外对室内颗粒物分布进行了大量研究，但湿度对室内颗粒物分布的影响仍不明确，本文主要通过完成以下几方面工作对其进行了初步研究：（1）简单介绍了室内颗粒物来源、粒径范围、浓度影响因素和对人体健康的危害后，又从理论研究、数值模拟和实验研究三方面阐述了室内颗粒物运动分布的国内外研究现状，总结出目前对室内颗粒物分布的研究均未考虑相对湿度的影响。（2）分析了单个颗粒在流场中受到的作用力，给出了颗粒输运方程、输运通量。计算了颗粒间的气体动力学碰撞及碰撞后导致凝并的相关作用力，得出相对湿度较大时，液桥力是颗粒物间凝并的主导作用力。（3）实验研究方面，为了排除温度变化对实验结果的影响和对比分析不同湿度条件下室内颗粒物分布的不同，在实验房间内建立了恒温恒湿控制系统，并通过调湿设置了几种相对湿度不同的工况。利用扫描电镜微观观察了颗粒源释放的颗粒、本底浓度及不同湿度条件下室内颗粒物的微观形态，发现只有相对湿度为65%以上的两种工况下，颗粒物之间才发生明显的凝并现象，不同粒径不同形态的小颗粒凝并生成不同粒径不同形态的大颗粒，且相对湿度越大，凝并现象越显著。利用粉尘检测仪、光学颗粒物粒径谱仪测试分析了不同工况下室内颗粒物的质量浓度、数密度和粒径分布，发现与其他工况相比相对湿度为80%时，室内颗粒物的质量浓度的衰减速度最小、0.3~2μm粒径范围内的颗粒物数密度衰减速度最小、0.3~1.5μm粒径范围内的颗粒物占总颗粒物百分比变化幅度也最小。最后对相对湿度为80%时，颗粒物质量浓度、数密度和粒径分布随时间变化曲线发生跳跃时的临界相对湿度值进行了研究。每种工况下的各项实验均进行了实验一和重复实验两次实验，结果表明实验的可重复性较好。（4）通过CFD方法，利用fluent模拟了工况1（RH=35%）下室内颗粒物的运动分布，对比实验数据说明了数值模拟的正确性，分析了室内流场和颗粒物质量浓度分布及其随时间变化情况。总的来说，相对湿度增大会改变颗粒物碰撞凝并的主要作用力，增强凝并效果，，使得更多的小颗粒凝并生成大颗粒，改变室内颗粒物的质量浓度、数密度和粒径分布，进而对室内颗粒物的分布造成影响。
[Abstract]:As one of the main pollutants in indoor air, the distribution of particulate matter in indoor air is very important to indoor air quality. Although much research has been done on indoor particulate matter distribution at home and abroad, the effect of humidity on indoor particulate matter distribution is still unclear. In this paper, a preliminary study was carried out in the following aspects: (1) after a brief introduction of indoor particulate matter sources, particle size range, factors affecting concentration and harm to human health, the theoretical study was carried out. In this paper, the present research situation of indoor particle movement distribution is described in terms of numerical simulation and experimental study, and it is concluded that the influence of relative humidity is not considered in the research of indoor particulate matter distribution at present. (2) the acting force of a single particle in the flow field is analyzed, and the particle transport equation and transport flux are given. The gas-dynamic collision between particles and the related forces leading to condensation after collision are calculated. It is concluded that the liquid bridge force is the leading force of coagulation between particles when the relative humidity is relatively high. (3) in order to eliminate the influence of temperature change on the experimental results and to compare and analyze the distribution of indoor particulate matter under different humidity conditions, a constant temperature and humidity control system was established in the experimental room. Several different working conditions of relative humidity are set up through humidification. The microscopic morphology of particles released from particle source, background concentration and different humidity were observed by scanning electron microscope. It was found that there were only two working conditions where the relative humidity was more than 65%. The phenomenon of coagulation and coalescence occurred only between particles. The smaller particles with different particle sizes and different shapes were coagulated, and the larger the relative humidity was, the more obvious the coagulation phenomenon was. Using dust detector and optical particle size spectrometer, the mass concentration, number density and particle size distribution of indoor particles under different working conditions were measured and analyzed. It was found that the relative humidity was 80 when compared with other working conditions. The attenuation rate of mass concentration of indoor particles was the smallest, the attenuation rate of particle number density was the least in the range of 0.3 渭 m and 1.5 渭 m, and the change range of particle percentage in the range of 0.3 渭 m and 1.5 渭 m was the smallest. At last, the critical relative humidity values of particle mass concentration, number density and particle size distribution when the relative humidity is 80 are studied when the curve of variation of particle mass density and particle size changes with time. Experiment 1 and repeated experiment were carried out under each working condition, and the results showed that the experiment was reproducible. (4) the movement distribution of indoor particulate matter under working condition 1 (RH=35%) was simulated by fluent by CFD method. The correctness of numerical simulation was proved by comparing the experimental data. The indoor flow field and particle mass concentration distribution and their variation with time were analyzed. In general, the increase of relative humidity will change the main force of particle collision condensation, enhance the coagulation effect, make more small particles coagulate and produce large particles, and change the mass concentration, number density and particle size distribution of indoor particles. Then the distribution of indoor particulate matter is affected.
【学位授予单位】：湖南工业大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：X513;TU834.8

【参考文献】