ASHRAE - American Society of Heating@ Refrigerating and Air-Conditioning Engineers@ Inc.
Scope
The energy use-related effects of ultraviolet germicidal irradiation (UVGI) to mitigate biological fouling (biofouling) of a chilled water cooling coil are investigated via a field study. A visibly bio-fouled cooling coil in an air-handling unit serving an operational building in a hot@ humid climate is monitored for 5 months to establish a fouled coil baseline. Parameters monitored include air flow rate@ airside pressure drop@ air temperature and humidity upstream and downstream of the coil@ chilled water flow rate@ entering and leaving chilled water temperature@ and waterside pressure drop. A UVGI coil irradiation system is installed on the downstream side of the coil following typical manufacturer guidelines@ and the system is then passively monitored over a period of 14 months. The change in operation is estimated by comparing data from the baseline and post-irradiation periods. The 95% confidence intervals for average improvement of coil airside pressure drop and heat transfer coefficient are 11.07% to 11.13%@ and 14.5% to 14.6%@ respectively. Complexities of the physical phenomena involved@ in particular@ the combined effect of airflow and latent load on airside pressure drop@ are taken into account.