Abstract
The evaporation of solution droplets and subsequent formation of solid particles may occur in a range of scenarios, for example, in an industrial spray drier, after a cough or sneeze, and in sea spray in the atmosphere. The processes that occur during droplet evaporation are governed by several kinetic competitions, which lead to dynamic behaviour as material and energy transfer between the droplet and gas environment. The state of drying droplets is may often considered as a binary transition: droplet to dry particle. However, a continuous process occurs with transient states which are poorly defined involved in defining the properties of the final dry particle. The properties of such particles are determined during the drying stage and so understanding of the drying and particle formation processes are essential to both accurate description of particle sources in release scenarios and to particle engineering challenges.This work presents the development of a novel instrument for parallel measurement of the geometric and aerodynamic size droplets as they dry and form solid particles, the development of a computational model for the simulation of the evaporation of binary solution droplets, and application of the two techniques to several inorganic salt solutions.
The experimental approach developed is a Falling Droplet Column (FDC), the key principles and components are described in this work alongside analysis techniques for the datatypes obtained. The FDC is used to measure droplet drying and particle formation processes, such as size and density change, with direct imaging of particles and then collect samples of particles for further analysis.
Interrogations of the evolving properties of particles formed from inorganic salt solutions, which are well parameterised, are presented and demonstrate the microphysical processes that occur within solidifying droplets. Additionally, measurements are made upon solutions of the industrial tracer material sodium fluorescein and respiratory surrogate fluids.
| Date of Award | 9 May 2023 |
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| Original language | English |
| Awarding Institution |
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| Sponsors | IRSN |
| Supervisor | Jonathan P Reid (Supervisor), Pascal Lemaitre (Supervisor) & Michael I Cotterell (Supervisor) |