异相凝结与同相凝结关系的实验研究

Experimental studies of the relationship between heterogeneous and homogeneous condensation

蒸发冷凝法气溶胶发生技术中,异相凝结有利于提高气溶胶的单分散性,同相凝结则会降低其单分散性,因此,如何避免同相凝结的发生从而提高气溶胶的单分散性是技术的关键。该文利用蒸发冷凝法气溶胶发生装置,通过调节凝结核浓度和蒸气压,研究了异相凝结和同相凝结的生长规律,并重点研究了2种凝结之间的竞争关系。研究表明,在凝结核浓度高于某临界值时,异相凝结可以抑制同相凝结的发生,并且在不同的总流量和蒸气压下,凝结核临界浓度值均在1.0×106个.cm-3附近。

With an evaporation-condensation aerosol generator, heterogeneous condensation improves the aerosol monodispersity, while homogeneous condensation degrades it. Therefore, the system must be designed to suppress homogeneous condensation to improve the aerosol monodispersity. The nuclei concentration and the vapor pressure in an evaporation-condensation aerosol generator were varied to analyze their effect on the heterogeneous and homogeneous condensation and the relationship between heterogeneous and homogeneous condensation. The experiments show that heterogeneous condensation may suppress homogeneous condensation when the nuclei concentration is above a critical value of approximately 1.0 × 10^6cm^-3 regardless of the total flow rate and the vapor pressure.