Detection of airborne particles by condensation method

凝结核计数器是一种通过水蒸气凝结到粒子上的超细气溶胶粒子探测器，它在直径小于0.1微米的气溶胶粒子的探测和分级中起着重要的作用。取得的结果如下：1.研究结果。对高流量(2.8 1/min和14 1/min)混合式数控系统进行了性能改进的基本分析，并对不同运行条件下的颗粒计数效率与数控系统形成的过饱和度的关系进行了评价。由过饱和度计算和实验发现，当过饱和度接近Becker-D6hring-Zeldvich经典成核理论所导出的临界过饱和度时，计数效率较高。这为开发高性能的数控机床提供了理论依据，最终研制的数控机床的性能总结为：对大于10 nm的颗粒计数效率为100%，对5 nm颗粒的计数效率为60%，流量为14I/min，是现有数控机床的50倍。研制成功了CNCA新型累积式电子迁移率分析仪与高流量(141/min)数控系统相结合的应用技术，该分析仪能够对5~100 nm的大气和室内气溶胶颗粒进行粒度分析。使用该原型数控系统的其他应用技术还包括具有非常高的收集效率(99.9999999%)的膜式气体过滤器的测试方法、超细颗粒在表面沉积速度的评估以及用气雾化方法检测水中的细菌和可溶性杂质的技术。

Condensation nucleus counter (hereafter CNC), a detector for ultra-fine aerosol particles by condensation of vapor onto the particles, which plays an important role in detection and sizing of aerosol particles smaller than 0.1) mum in diameter, has been studied from the view points of fundamental analysis to improve its performance and application techniques combined with it. The results obtained are as follows.1. Fundamental analysis for improvement in performance of CNCHigh flow rate (2.8 1/min and 14 1/min) mixing type CNC's were developed and evaluated the particle counting efficiency as the function of supers aturation formed in CNC's at various, operating conditions. it was found from the calculation of supersaturation and experiment that high counting efficiency was attained at the supersaturation as close as to the critical one derived from the classical nucleation theory proposed by Becker-D6hring-Zeldvich, where homogeneous nucleation was initiated. This fact gave us a theoretical criterion for developing high performance CNC'S. The performance of the CNC thus finally developed is summarized as follows : particle counting efficiency of 100% for particles larger than 10nm, efficiency of 60% for 5nm particles, and the flow rate of 14 I/min which is 50 times as high as existing CNC's were attained.2. Application techniques using CNCA new cumulative type electrical mobility analyzer combined with high flow rate (14 1/min) CNC above developed has been successfully developed, and it was found that the analyzer was capable of size analysis for atmospheric and room aerosol particles ranging 5-100nm in diameter. other application techniques using the prototype CNC include those for testing method of membrane gas filters having very high collection efficiency (99.9999999%), evaluation of deposition velocity of ultra-fine particles onto surfaces, and those for detecting bacteria and soluble impurities in water by aerosolizing method.