Is line-source modeling suitable for ultraviolet light application in an air cleaner duct?

Authors: LI, PEIYANG - Iowa State University; Koziel, Jacek; YEDILBAYEV, BAUYRZHAN - Al-Farabi Kazakh National University; PARIS, VINCENT - Iowa State University; WALZ, WILLIAM - Iowa State University; RAMIREZ, BRETT - Iowa State University

Submitted to: Frontiers in the Built Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/19/2024
Publication Date: 3/1/2024
Citation: Li, P., Koziel, J.A., Yedilbayev, B., Paris, V.R., Walz, W.B., Ramirez, B.C. 2024. Is line-source modeling suitable for ultraviolet light application in an air cleaner duct? Frontiers in Built Environment. 10:1325267. https://doi.org/10.3389/fbuil.2024.1325267.
DOI: https://doi.org/10.3389/fbuil.2024.1325267

Interpretive Summary: Clean and safe air is essential in residential and workplace settings, including agricultural production and food supply chains. The public is concerned with resurgence of diseases, such as COVID-19, that infect via inhaled air. Ultraviolet (UV) light is known to be effective in disinfecting air. However, it is still challenging to properly design practical UV disinfection applications for indoor air. In this research, a team of engineers and scientists from ARS-Bushland (Texas), Iowa State University, and Kazakh National University developed a practical model for improved estimation of effective UV doses for technology such as portable air cleaners and heating, ventilation, and air conditioning (HVAC) ducts with built-in UV lights. It was found that the light dissipates with distance, following a simple inverse correlation, particularly in tight space near UV light bulbs. This finding is important for designing effective UV light disinfection applications typical in indoor air. The public and many stakeholder groups are interested in lowering the risk and mitigating the spread of airborne diseases.

Technical Abstract: Ultraviolet-C germicidal light can be effective in inactivating airborne pathogens and mitigating the transmission of infectious diseases. As the application of UV-C for disinfection gains popularity, practical estimation of UV irradiance is essential in determining the UV fluence (dose) and designing tubular UV lamp configurations for indoor air treatment. It is generally understood that the inverse square distance (~1/d2) law applies well to point light sources. However, there has been a recognition that the ~1/d2 law does not work well for tubular light sources in the commonly defined near-field applications where the UV source is relatively close to the treated air. Practical modeling solutions for near-field irradiation estimation are therefore needed for technology such as portable air cleaners and HVAC ducts with built-in UV light bulbs. This research investigated UV-C light irradiance from tubular (L = 0.9 m) light bulbs at near distances inside an air cleaner prototype duct under three power output (1-, 4-, and 8-bulb) scenarios and also conducted theoretical estimation based on line-source irradiation models. Similarly sized visible fluorescence bulbs were used as a reference. The data were fitted on both the ~1/d2 and ~1/d correlation of irradiance with distance. Both measured and line source estimated data fit better (i.e., evaluated by R2, standard errors, root mean squared errors) with the ~1/d than with ~1/d2 relationship in near distance. It is recommended that the inverse (~1/d) correlation be used for near-distance estimation of light distribution, especially for disinfection purposes in air ducting for indoor air quality improvement and airborne disease mitigation.