Experimental study of heat and mass transfer in CO2 frost formation on a cryogenic cylinder

• An experimental setup has been designed to measure CO 2 frost thickness and mass deposition rates. • Frost porosity increases as both the Reynolds and Grashof numbers increase. • Frost density and thermal conductivity have an inverse dependence on Re and Gr. • An empirical relationship has been proposed to relate frost density to the Re, Gr and time. Cryogenic carbon capture (CCC) is one of the fastest-growing technologies for CO 2 emissions reduction. The fundamental basis of the technology is the ability of CO 2 to desublimate (gas to solid phase change) at temperatures and pressures below its triple point (-56.6°C, 5.1 atm). This allows for selective CO 2 separation from industrial gas streams in processes like natural gas sweetening and flue gas CO 2 stripping. The properties of CO 2 frost accumulated on surfaces in the CCC process are understudied. Most previous studies have focused on water frost, especially on aircraft wings. While correlations derived from water frost provide valuable insights, they are not fully representative of CO₂ frost behavior. This study focuses on the experimental investigation of the impact of Reynolds (Re) and Grashof (Gr) numbers on the properties of CO 2 frosts accumulated on a cylindrical cryogenic surface. A simulated flue gas composed of N 2 and CO 2 with a CO 2 concentration of 17% was used in all experiments. 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. Increasing the Re leads to lower CO 2 mass accumulated but higher frost thickness. 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. Increasing the Grashof number reduces the frost with time. The findings provide valuable insights into the coupled heat and mass transfer mechanisms governing frost growth during CO₂ desublimation.