Author(s): Mingming Ge; Joseph H. W. Lee; Ruipeng Li; Dixia Fan

Linked Author(s): Mingming Ge

Keywords: Water treatment; Hydrodynamic cavitation; Cavitation intensity; Cavitation shedding regimes; Thermodynamic effects

Abstract: Hydrodynamic or acoustic cavitation combined with advanced oxidation processes (AOPs) is a promising alternative to the technologies of wastewater treatment technologies in use today. Cavitation combined with AOPs shows their effectiveness in water disinfection and oxidizing organic contaminants such as pharmaceuticals, organic dyes, and insecticides. The analysis of the economics of the treatment processes performed to evaluate the possibility of scaling up reveals that the economic operations should be based on hydrodynamic cavitation. Venturi-type cavitation reactors can be one of the most promising candidates for industrial-scale production due to their cheapness and ease of construction, scaling, and replicability. The effects of temperature on hydrodynamic cavitating flow in a Venturi section are investigated to find the optimum reacting conditions enhancing cavitating treatment intensity. The flow conditions are varied with different flow rates and a wide range of temperatures between 28 °C to 63 °C. Results show that both the cavitation length and the transition between sheet and cloud cavitation regimes are influenced by a combination of the pressure drop (indicated by the cavitation number σ), the inertial/viscous effects (controlled by the Reynolds number Re), and the thermal effect (indicated by the thermodynamic parameter). As the temperature is elevated, both the cavitation length and thickness increase first, and then decrease. The cavitation intensity peaks at a transition temperature of 58 °C. With the rise of cavitation length and thickness, the regimes tend to switch earlier from the attached sheet cavity to periodical cloud shedding, and the shedding frequency decreases accordingly. This study allows us to understand the instability, size evolution, and shedding regime transition of partial cavities considering thermodynamic effects. Recommendations are provided to water treatment industries that working under a 55 °C to 60 °C temperature range will attain the highest cavitation intensity.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p0077-cd

Year: 2023