Committee Members

• Ph.D. Advisor: Professor William Roberts (KAUST, Mechanical Engineering)
• External Examiner: Professor Tiegang Fang (Department of Mechanical and Aerospace Engineering, North Carolina State University)
• Committee Chair: Professor Tadd Truscott (KAUST, Mechanical Engineering)
• 4th Committee Member Professor:  Javier Ruiz Martinez (KAUST, Chemical Engineering)

Abstract

Cryogenic carbon capture (CCC) is one of the fastest-growing technologies for CO₂ emissions reduction. The fundamental basis of the technology is the ability of CO₂ to desublimate (gas to solid phase change) at temperatures and pressures below its triple point (-56.6 °C, 5.2 atm). This allows for selective CO₂ separation from industrial gas streams in processes like natural gas sweetening and flue gas CO₂ stripping. The properties of CO₂ frost accumulated on surfaces in the CCC process are understudied.

Most previous studies have focused on water frost, especially on aircraft wings. This dissertation focuses on the experimental and numerical investigation of the impact of flow field and temperature on the properties of CO₂ frosts accumulated on cryogenic solid surfaces of a coin and copper tube while also exploring CO₂ behavior in a low temperature volatile liquid (Isopentane). The CO₂ & N₂ bubble dynamics in low - temperature isopentane was investigated as a foundation for further CO₂ desublimation studies.

A simulated flue gas of varying CO₂ compositions (16.2%, 17% & 100%), were used in the experiments. For solid surfaces, our analysis reveals the significant influence of Reynolds (Re) and Grashof (Gr) numbers on frost deposition rate, thickness evolution, effective thermal conductivity, and void fraction.

The findings further show that frost thickness is not representative of the mass of frost accumulated with time, as is usually assumed in 1D-simulation cases. In the liquid surface experiments, CO₂ solubility in isopentane increases at lower temperatures; however, above -20 °C, isopentane vaporises into rising CO₂ bubbles, significantly influencing their size and dynamics.