Simulation-based Performance and Life-Cycle Cost Evaluation of In-duct Ultraviolet Germicidal Irradiation Systems

Open Access
Author:
Lee, Bruno
Graduate Program:
Architectural Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
October 02, 2009
Committee Members:
  • William P Bahnfleth, Thesis Advisor
Keywords:
  • Ultraviolet germicidal irradiation
  • UVGI
  • UVC lamp performance
  • Airborne contaminant control
  • Indoor air quality
  • Life-cycle cost analysis
  • LCC
Abstract:
In-duct ultraviolet germicidal irradiation (UVGI) systems treat moving airstreams in heating, ventilation, and air-conditioning (HVAC) systems to inactivate airborne microorganisms. UVGI system performance depends on air temperature, airflow velocity, variations in exposure time and other parameters. These parameters are generally functions of time. There is a lack of investigation in the current literature on the operation of UVGI systems over extended periods to capture the effects of these time-varying parameters. This research investigates a simulation-based evaluation procedure that considers the effect of time-varying parameters on the performance and life-cycle cost of in-duct UVGI systems. The evaluation procedure is applied to a hypothetical commercial building in a parametric study that investigates UVGI systems designed for different design strategies, installation locations, and geographical locations. The results are also compared to those provided by ventilation and filtration. For the reference case of inactivating S. aureus, UVGI air treatment results in lower predicted space concentrations than those provided by elevated ventilation with respect to ASHRAE Standard 62.1, and similar levels to those achieved by high-efficiency filtration at a lower cost. Cost increases proportionally with performance; therefore, it is very important to ensure the performance target is marginally met for the desired percentage of time to avoid over or under sizing the UVGI system in order to control cost. This design methodology can possibly only be done with a simulation-based evaluation procedure. Uncertainties in modeling assumptions result in uncertainties in the simulated performance and life-cycle cost. Sensitivity analysis provides an insight into the amount of possible variation around the predicted values. The results of the parametric study suggest that a simulation-based evaluation procedure is an indispensable tool in the design process of UVGI systems. The procedure presented in this research can be further refined and incorporated into design practice in the future.