Computational Fluid Dynamic Modeling of In-duct UV Air Sterilisation Systems.

In-duct UVC air sterilisation is a technology that can help in the reduction and control of airborne diseases. Nevertheless, improvements in sterilisation performance efficiency are required for the technology to succeed in an increasingly restricted energy society. Computational fluid Dynamics (CFD) was used to systematically improve the performance of in-duct UVC air sterilisation systems. The Discrete Ordinates method (DO) was used to model lamp irradiation, and a user defined function (UDF) to model the injection of microorganisms inside the duct to then calculate the average UV dose of the system, with this it was possible to reproduce test results published by EPA. After the CFD model was validated, operation parameters such as wall reflectivity, lamp location, lamp position, air velocity and airflow patterns were analysed. It was found that accurate information of UVC susceptibility for microorganisms in air was essential for the correct modeling of UVC air sterilisation systems using CFD, and current available data contain considerable variations that needed to be analysed and interpreted in an appropriate manner. It was also found that the DO method was appropriate to model lamp irradiation and could account for reflectivity, and that CFD was robust enough to reproduce lab tests results. Moreover it was found that airflow patterns, and lamp location and position influenced the sterilisation performance of a UVC system. Results include a comprehensive list of microorganisms UVC susceptibilities in air (Chapter 3); a set of CFD models that can be used for validation or calibration for future studies and a confirmation that CFD is capable to model in-duct UVC air sterilisation systems (Chapter 5). Ultimately this research presents a series of conclusions that will help on the design of more efficient in-duct UVC air sterilisation systems.