Airflow and Contaminant Distribution in Hospital Wards with a Displacement Ventililation System

Airflow and Contaminant Distribution in Hospital Wards with a Displacement Ventilalation System. The 2nd International Conference on Build Environment and Public Health, BEPH 2004, Shenzhen , China . ABSTRACT Displacement ventilation has not been considered to be an applicable system for hospital wards probably due to its inability to remove large particles and risk of particle deposition on horizontal surfaces in the occupied regions. However, the existing downward ventilation system commonly used in isolation rooms does not deliver the required performance. There is a need to develop effective ventilation system in hospital wards. It is for this purpose that we study the performance of displacement ventilation in hospital wards as one of the steps to optimize the ventilation design. When the prospect of applying displacement ventilation system in a hospital ward is examined, it should be necessary to accurately predict three-dimensional distribution of air velocity, temperature, and contaminant concentration in the ward. Indoor airflow in a displacement ventilation system involves a combination of different flow streams such as the gravity currents and thermal plumes. It is important to choose an appropriate turbulent model to simulate and reproduce the process of contaminant dispersion. The low Reynolds-number (LRN) k-e (Launder and Sharma, 1978) turbulence model with a damping function (Chikamoto et al., 1992) was considered and evaluated by experiment. We carried out an experimental study to test the performance of the displacement ventilation system in a hospital ward. The results of LRN k-e model with damping function agreed well with the measured data. Furthermore, the flow pattern showed by the calculated age of air agreed well with observed flow pattern by smoke visualization. The CFD results assisted us to understand the contaminant dispersion. It was shown that the interaction of exhaled flow and the body thermal plume generated by manikin would affect exhaled virus-laden aerosols distribution in the ward with displacement ventilation system.