Role of dissolved CO2 in hydrodynamic cavitation on a chip

Official URL: https://dx.doi.org/10.1016/j.ijmultiphaseflow.2025.105526

This study presents an experimental investigation of hydrodynamic cavitation (HC) in two microfluidic chips (microscale HC chips) under varying flow patterns (upstream pressure and local temperature), with and without dissolved CO₂. High-speed imaging and spectral analysis were used to characterize cavitation inception, vapor cloud formation, void fraction, and bubble dynamics (frequency spectra) under the effect of the dissolved gas in micro domains. The results show that higher upstream pressure substantially intensifies cavitation, while the presence of dissolved CO₂ lowers the pressure threshold for cavitation inception and amplifies cavitation activity. The micro-step chip (Reactor 1) presented more intense cavitation and a greater vapor void fraction than the long-diaphragm chip (Reactor 2) across all conditions. Notably, dissolved CO₂ suppressed high-frequency bubble-collapse fluctuations and induced a transition from violent cloud-shedding cavitation to a stable, continuous bubbly flow regime. Additionally, cavitation facilitated significant CO₂ degassing, removing up to ∼30% of the dissolved gas in Reactor 1 (versus ∼11% in Reactor 2) under the similar conditions. The results also show that temperature significantly influenced CO₂ removal efficiency, with the highest elimination (52%) occurring at 25°C, where high gas solubility and low vapor pressure were optimally balanced. These findings highlight the coupled influence of pressure, temperature, and dissolved gas on “HC on a chip” concept and provide fundamental insights into multiphase flow dynamics and bubble–fluid interactions, offering guidance for controlling microscale cavitation and bubble-mediated transport phenomena.