Computational fluid dynamics modelling and optimisation of an upper-room ultraviolet germicidal irradiation system in a naturally ventilated hospital ward

Ultraviolet germicidal irradiation (UVGI) has been shown to be an effective technology for reducing the airborne bioburden in indoor environments and is already advocated as a potential infection control measure for healthcare settings. However, much of the understanding of UVGI performance is based on experimental studies or numerical simulation in mechanically ventilated environments. This study considers the application of an upper-room UVGI system in a naturally ventilated multi-bed hospital ward. A computational fluid dynamics model is used to simulate a Nightingale-type hospital ward with wind-driven cross-ventilation and three wall-mounted UVGI fixtures. A parametric study considering 50 different fixture configurations and three ventilation rates was carried out using a design of experiments approach. Each configuration was assessed by calculating the UV dose distribution over the ward and at each bed. Results show that dose is influenced by the location of the fixtures and the ventilation regime. Thermal effects are likely to be important at low ventilation rates and may reduce UV effectiveness. A metamodel-based numerical optimisation was applied at a ventilation rate of 6 air changes per hour. In this case, the optimum result is achieved when UVGI fixtures are mounted on the leeward wall at their lowest mounting height.