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Shahrasebi, Maryam

University of British Columbia

Marine Cloud Brightening (MCB) has been proposed as a technique to produce local or regional cooling over remote oceans. The underlying principle of MCB is to artificially enhance the reflectivity and longevity of the maritime stratocumulus clouds by injecting seawater aerosols at low elevations (~1 km), where they act as cloud condensation nuclei. However, the presence of giant (1-10 microns) cloud condensation nuclei (CCN) within the seeded size spectrum expedites precipitation, which may break up the cloud layer. A critical challenge in MCB is the development of energy-efficient methods for generating and dispersing CCN of the optimal size range (30-500 nm). This thesis investigates the potential of splash-plate atomization (SPA) as a novel and efficient technique for MCB applications. SPA utilizes jet impingement on an inclined plate to generate a thin liquid sheet that subsequently breaks into droplets of a size comparable to the sheet thickness, rather than the orifice diameter, offering control over droplet size distribution. An experimental setup has been developed, including a SPA unit, a sampling room, and instrumentation for characterizing particle size distribution. To complement the aerosol size measurements, shadowgraph imaging has been performed, allowing for the visualization and analysis of the spray dynamics. The performance of the SPA system has been evaluated under various operating conditions, including different pumping pressures (1000, 1400, and 2000 psi), different spray deflection angles (75,60,45, and 30 degrees jet deflections), and different plate lengths (edge-proximal and edge-distant). To evaluate the performance of SPA, we measure the energy consumed by SPA from liquid flow and pressure, and with the size distribution, we estimate the energy required for a particle of the correct size. The results demonstrate that SPA can generate droplets in the size range suitable for MCB with energy consumption (in the order of 10^(-9) J/particle) comparable to existing state-of-the-art atomizers. We conclude that: Pressure has the strongest influence on droplet size distribution. Shortening the plate length improves particle production, making edge-proximal deflection more effective for MCB. A 60-degree edge-proximal deflection generates the highest number of suitable particles for the same energy.

Text

2024-12-16

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/89891

Mechanical Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/