Onset conditions for agglomeration of CO₂ snow inside a tube

Carbon dioxide (CO₂) snow jets are widely used in medical and industrial applications, such as cryogenic therapy, food processing, pharmaceutical granulation, particle removal and surface cleaning. In semiconductor fabrication, CO₂ snow cleaning has unique organic and particle removal abilities with eco-friendly that are better than those of traditional surface cleaning methods. A model for the agglomeration of CO₂ snow particles is derived by our research team this year, and it provide clear evidence of the agglomeration of CO₂ snow inside a tube that has never been published in the literature and indeed providing highly opportunity to advance performance of CO₂ cleaning. To prolonging the research results of agglomeration mechanism of primary CO₂ snow, this research aim at the controlling-technologies of snow particles, include the onset mechanism and onset length of agglomeration of snow particle. By using the additive manufacturing method by 3D printer, complicated design with converging-diverging configuration and curved surface can easily be realized. This paper experimentally investigates the agglomeration mechanism of CO₂ primary particles inside a tube. Results show that a complicated particle motion in the upper portion of the tube is responsible for the formation of large snow. A minimum tube length of 30mm, onset condition, is needed to ensure the complete formation of agglomerated mechanisms with recirculation flow, and thus ensure the formation of considerable agglomerated particles. Results also show that the onset condition of agglomeration is influenced by the flow condition, as well as the lucking of the main flow.