Abstract

The origin of ions in the lower atmosphere is attributed to sources like galactic cosmic rays, radioactive isotopes, gamma radiation, etc. These ions interact with atmospheric constituents affecting various atmospheric processes. Aerosol microphysical processes also get modified due to the presence of charge on particles. For aerosol generation, charging during generation and consequent effect on evolution dynamics is an important aspect. One of the efficient methods for the generation of nanaoparticle aerosols is via electrically heated wires i.e. hot wire generator (HWG). Although studies exist focusing on experimental insights, not much work has been performed in the direction of modeling the process for HWG systems. At present, there is a knowledge gap in the detailed understanding of charged aerosol microphysics of such high temperature systems. Models have been developed for different aspects of charged particles; but to the best of our knowledge, there are no studies which model the complete process for a hot wire generator, factoring both the effect of charge and Computational Fluid Dynamics (CFD). A CFD coupled aerosol microphysical model was developed for HWG in our earlier work. Charge has been added in the modified theoretical framework for the present work. The modified charged aerosol dynamic model has been coupled to the module for ion generation from hot sources. Thus, a newly developed CFD coupled charged aerosol microphysical model has been used for modeling the nanoparticle generation from HWG system. Results from the simulations have been compared with the experimental observations performed with a laboratory made HWG.

Copyright © 2021 American Association for Aerosol Research

摘要

低层大气中离子的来源归因于银河宇宙射线、放射性同位素、伽马辐射等来源。这些离子与影响各种大气过程的大气成分相互作用。由于粒子上存在电荷，气溶胶微物理过程也会发生改变。对于气溶胶生成，生成过程中的充电以及随之而来的对演化动力学的影响是一个重要方面。产生纳米粒子气溶胶的有效方法之一是通过电加热线，即热线发生器 (HWG)。尽管存在侧重于实验见解的研究，但在为 HWG 系统的过程建模的方向上没有进行太多工作。目前，在详细了解此类高温系统的带电气溶胶微观物理学方面存在知识空白。已经针对带电粒子的不同方面开发了模型；但据我们所知，还没有研究模拟热线发生器的完整过程，同时考虑电荷和计算流体动力学 (CFD) 的影响。在我们早期的工作中，为 HWG 开发了 CFD 耦合气溶胶微物理模型。在当前工作的修改后的理论框架中添加了电荷。修改后的带电气溶胶动力学模型已耦合到用于从热源生成离子的模块。因此，新开发的 CFD 耦合带电气溶胶微物理模型已用于模拟 HWG 系统的纳米颗粒生成。

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