Mapping the performance of a versatile water-based condensation particle counter (vWCPC) with numerical simulation and experimental study
Mapping the performance of a versatile water-based condensation particle counter (vWCPC) with numerical simulation and experimental study
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DOI：
10.5194/amt-16-3973-2023
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发表时间：
2023-09
影响因子：
3.8
通讯作者：
Weixing Hao;F. Mei;Susanne Hering;Steven Spielman;Beat Schmid;Jason Tomlinson;Yang Wang
中科院分区：
文献类型：
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作者：
Weixing Hao;F. Mei;Susanne Hering;Steven Spielman;Beat Schmid;Jason Tomlinson;Yang Wang
抽象。精确的气溶胶仪器是确定环境气溶胶粒子的空间分布，特别是在处理复杂的垂直剖面和水平变化的大气气溶胶。已经开发了一种多功能水基冷凝颗粒计数器（vWCPC），以提供在各种环境下的气溶胶浓度测量，其优点是减少与使用丁醇或其他化学品作为工作流体相关联的健康和安全问题。然而，由于缺乏vWCPC在减压下的性能表征，vWCPC的机载部署相对有限。鉴于vWCPC中操作参数的复杂组合，建模研究在绘制vWCPC性能方面具有优势。在这项工作中，我们使用COMSOL Multiphysics®模拟结合MATLAB™，彻底研究了层流vWCPC的性能。我们将其与改良的vWCPC（vWCPC型号3789，TSI，Shoreview，MN，USA）进行了比较。通过模拟计算，确定了vWCPC生长管中颗粒活化和液滴生长的性能，包括过饱和度、Dp、kel、0（可活化的最小颗粒尺寸），Dp，kel，50（以50%效率活化的颗粒尺寸）分布，以及在宽的操作温度、入口压力P（30-101 kPa）和生长管几何形状（直径D和引发剂长度Lini）。还研究了入口压力和调节器温度对vWCPC 3789性能的影响，并与实验室实验进行了比较。COMSOL模拟结果表明，增大调节温度Tcon与引发温度Tini之间的温差（ΔT），会降低vWCPC的Dp，kel，0和截止粒径Dp，kel，50。此外，降低温度中点（Tmid=Tcon+ Tini 2）增加过饱和度并略微降低Dp，kel。生长管末端的液滴尺寸并不显著依赖于升高或降低温度中点，但在降低的入口压力下显著降低，这间接改变了vWCPC经验截止尺寸。我们的研究表明，当前模拟生长管几何形状（D=6.3 mm和Lini=30 mm）是当前vWCPC流量和温度设置的最佳选择。当前模拟可以更真实地表示7 nm vWCPC的Dp，kel，并且与2 nm设置也实现了良好的一致性。使用新的模拟方法，我们提供了一个优化的操作设置为7 nm的设置。这项研究将指导进一步vWCPC性能优化的应用程序需要精确的粒子检测和大气气溶胶监测。
Abstract. Accurate airborne aerosol instrumentation is required to determine the spatial distribution of ambient aerosol particles, particularly when dealing with the complex vertical profiles and horizontal variations of atmospheric aerosols. A versatile water-based condensation particle counter (vWCPC) has been developed to provide aerosol concentration measurements under various environments with the advantage of reducing the health and safety concerns associated with using butanol or other chemicals as the working fluid. However, the airborne deployment of vWCPCs is relatively limited due to the lack of characterization of vWCPC performance at reduced pressures. Given the complex combinations of operating parameters in vWCPCs, modeling studies have advantages in mapping vWCPC performance. In this work, we thoroughly investigated the performance of a laminar-flow vWCPC using COMSOL Multiphysics® simulation coupled with MATLAB™. We compared it against a modified vWCPC (vWCPC model 3789, TSI, Shoreview, MN, USA). Our simulation determined the performance of particle activation and droplet growth in the vWCPC growth tube, including the supersaturation, Dp,kel,0 (smallest size of particle that can be activated), Dp,kel,50 (particle size activated with 50 % efficiency) profile, and final growth particle size Dd under wide operating temperatures, inlet pressures P (30–101 kPa), and growth tube geometry (diameter D and initiator length Lini). The effect of inlet pressure and conditioner temperature on vWCPC 3789 performance was also examined and compared with laboratory experiments. The COMSOL simulation result showed that increasing the temperature difference (ΔT) between conditioner temperature Tcon and initiator Tini will reduce Dp,kel,0 and the cut-off size Dp,kel,50 of the vWCPC. In addition, lowering the temperature midpoint (Tmid=Tcon+Tini2) increases the supersaturation and slightly decreases the Dp,kel. The droplet size at the end of the growth tube is not significantly dependent on raising or lowering the temperature midpoint but significantly decreases at reduced inlet pressure, which indirectly alters the vWCPC empirical cut-off size. Our study shows that the current simulated growth tube geometry (D=6.3 mm and Lini=30 mm) is an optimized choice for current vWCPC flow and temperature settings. The current simulation can more realistically represent the Dp,kel for 7 nm vWCPC and also achieved good agreement with the 2 nm setting. Using the new simulation approach, we provide an optimized operation setting for the 7 nm setting. This study will guide further vWCPC performance optimization for applications requiring precise particle detection and atmospheric aerosol monitoring.