2026-09-21T20:44:24Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/132627 2026-03-24 col_2142_5131 col_2142_14787 com_2142_5130 com_2142_9630 com_2142_234

application/pdf en text Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2027-12-01 The student, Zhiyu Zhao, accepted the attached license on 2025-09-30 at 21:34. The student, Zhiyu Zhao, submitted this Thesis for approval on 2025-09-30 at 21:45. This Thesis was approved for publication on 2025-10-06 at 15:11. DSpace SAF Submission Ingestion Package generated from Vireo submission #22818 on 2026-02-19 at 18:45:35 Modeling and measurement of sodium chloride and ammonium sulfate droplet growth in laminar flow Zhao, Zhiyu 2025-10-06 Brewster, M. Quinn droplet growth eng Cloud droplet growth is governed by a balance between vapor diffusion, Kelvin effect, and Raoult’s law, as expressed in K¨ohler theory. In this study, a thermodynamic droplet growth framework initially developed by Brewster and Li (2021) for radiation-induced cooling of pure water droplets is extended to include the effects of dissolved salts through an ion-number-based weighting in the Kelvin–Raoult balance. Two atmospherically relevant salts—sodium chloride (NaCl) and ammonium sulfate ( (NH4)2SO4)—are investigated at multiple concentrations in a controlled laminar-flow environment. Droplets are generated via ultrasonic nebulization, transported through a polyethylene tube under well-characterized temperature and humidity, and measured using optical particle sizing at multiple downstream positions. The model predicts the temporal evolution of droplet radius by solving the coupled mass and heat transfer equations with supersaturation determined from the modified K¨ohler equilibrium. Results show that the extended model captures the droplet size distribution’s primary mode diameter and general shape for both salts across the tested concentrations. Higher ion yield and molar mass effects for ( NH4)2SO4 lead to greater growth enhancement compared to NaCl, consistent with the Raoult term’s suppression of equilibrium vapor pressure. Discrepancies at high solute concentrations and in the large-droplet tail (> 20 μm) are attributed to neglected hydrodynamic coalescence and concentration-dependent surface tension effects. This work demonstrates that pure water thermodynamic growth models can be extended to salt droplets with modifications, providing a validated basis for parameterizing cloud and climate models. 2025-12 Thesis https://hdl.handle.net/2142/132627 Copyright 2025 Zhiyu Zhao Mechanical Sci & Engineering Mechanical Engineering University of Illinois Urbana-Champaign M.S. Thesis