Researchers at Penn State are investigating the use of ultraviolet germicidal irradiation (UVGI) as a long-term maintenance solution for cooling coils in heating, ventilation and air conditioning (HVAC) systems in buildings.
The research, conducted by William Bahnfleth, professor of architectural engineering, and alumnus Joseph Firrantello ('07 B.A.E., '07 M.S., '16 Ph.D.), is a field study that involved the installation of sensors to collect temperature, humidity, air flow and pressure drop data on HVAC cooling coils before and after UVGI was used to clean away the buildup of microorganisms. The project uses the data collected from the field research to create models that estimate the potential energy and indoor air quality (IAQ) benefits of UVGI cleaning.
During normal operation, heat transfer coils in HVAC systems become polluted with microorganisms — primarily fungi and bacteria and other particulate matter in the air. This buildup leads to a loss of performance, both in lost heat transfer capacity and through the increased energy consumption that is needed to continue to move air through the system. Heat transfer coils are particularly vulnerable to contamination because of the condensation that forms on them and the fins that make up the system.
Ultraviolet irradiation in the UVC band is an alternative or adjunct to mechanical and chemical cleaning options. Bahnfleth said UVGI systems are currently available from many manufacturers, but due to the lack of independent research and analysis to document the effectiveness of UVGI coil cleaning, their use is limited.
“UVGI has been used for water, air and surface disinfection for over 100 years, but applications to control indoor air quality have not been as well studied as they should, leading to questions about the effectiveness and safety of this technology,” Bahnfleth said. “Through our work, we hope to answer important questions about how well UVGI works under different conditions, when its use should be considered, and whether there are safety issues associated with its use that need to be addressed.”
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