A Numerical and Experimental Study on a Hybrid In-Duct Disinfection System of Ultraviolet and Bipolarity Air Ions

Description

Airborne transmitted pathogen infection can cause various diseases and severely threaten human health and lives. In highly crowded and enclosed environments such as health-care facilities, large shopping malls, commercial buildings, and public buildings, human-generated indoor pathogens may be transmitted, dispersed, and lead to cross-infection in people through heating, ventilation and air conditioning (HVAC) systems. Infection can also affect work productivity and have a substantial economic impact.To reduce infection risk, several engineering strategies can be implemented: increasing ventilation rates, using high efficiency filtration systems, and adopting active disinfection systems. In many scenarios, the first two options are very energy costly in the long-term and are not feasible for many premises. Due to their low pressure drop, ultraviolet germicidal irradiation (UVGI) and electrical corona wire ionization have been introduced to HVAC markets as alternative technologies.Studies have demonstrated that these installations are effective in the stationary phase. However the disinfection efficacy decreases with airflow velocity. Even worse, ozone gas is generated as a by-product. Literature on measuring their disinfection efficacy for HVAC systems is rare. No systematic study has investigated how to improve and optimize these two technologies. Technical information on maximizing the performance is lacking.The project will aim to propose a feasibility study on developing an optimal, energy efficient and high efficacy in-duct disinfection system for HVAC installation under practical scenarios. The system will be hybridized by a modified UV-C and a corona pin-type ionization system. In the first stage, the UVGI and the pin ionization system will be studied alone. By designing an optical system, the irradiation zone and intensity of the UVGI lamps will be magnified and a more uniform irradiation zone will be formed. A new bipolarity pin ionization system using carbon fiber as emission tips will be fabricated. Different types of bacteria will be selected to cover a wide range of sizes. Synergetic effect will be investigated to further enhance the performance. Scanning electronic microscopy and atomic force microscopy will be used to study the disinfectionmechanisms by examining cellular structure changes after exposure to the active systems. In addition, a computational tool will also be developed. The UV irradiation, air ion transport, microorganism continuity equations will be solved.The results and deliverables of this proposal will provide valuable information for future development of new methods for controlling indoor microorganisms. In the future, fewer indoor airborne pathogens can be achieved with low energy implication.?