凝聚核粒子计数器是一种纳米级颗粒物的检测装置, 本文对该仪器的冷凝段进行了理论分析及数值模拟。数值模拟采用四点有限差分隐式法和Crank-Nicolson 法, 使用不等间距网格。结果显示四点有限差分隐式法模拟结果的稳定性和精确性良好, 并与前人的研究结果基本一致。在数值上对剑桥大学提出的高温凝聚核粒子计数器的可行性进行验证, 模拟结果显示, 高温下工作的凝聚核粒子计数器切割粒径为4 nm, 能够去除挥发性物质的影响。研究验证, 由于工质冷凝在颗粒表面而导致的工质损失以致过饱和度降低的影响可忽略不计。
This paper reports the theory and modeling of a nanoparticle monitor, the condensation particle counter. A four-point finite difference implicit approach and Crank-Nicolson approach are utilized for the model and nonuniform grids are adopted. The simulated results have revealed that the four-point finite difference implicit approach is in good agreement with the previous studies, while the stability and precision are improved. This paper numerically validates the feasibility of high temperature condensation particle counter, which was proposed by Cambrige to replace the existing particle measurement program. The result shows that the cut-off size is 4 nm, thus eliminating the effect of volatile compounds. At last, the depletion of working medium is verified, which is caused by working fluid condensing on the particles, thus lowering saturation ratio can be safely neglected.
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