Influence of vertical airflow along walls on temperature and contaminant concentration distributions in a displacement-ventilated four-bed hospital ward

In hospital wards, unpleasant odors from the human body and excreta are a troublesome problem that leads to a poor indoor air environment. Displacement ventilation (DV) can provide good air quality to the lower part of the room (the occupied zone), especially when the contaminant is combined with the plume from a heat source. Hence, it is believed that DV could be an efficient way to remove unpleasant odors from wards. However, if DV is used in a room containing a window or a poorly insulated wall, the convention airflow along the vertical surface during the cold and hot season will affect the indoor environment of the room. To investigate the influence of this downward and upward airflow on indoor air quality in a displacement-ventilated ward, full-scale experiments were conducted in an environmental chamber simulating a four-bed hospital ward. The temperature and contaminant concentration distributions were measured under various conditions regarding the temperature difference between the wall surface and room air. Consequently, downward convection airflow considerably affected the contaminant concentration in the occupied zone. As the downward airflow rate increased, the contaminant concentration in the lower part of the room also increased. Additionally, the zonal model for predicting the temperature and contaminant concentration was also validated and the calculated results corresponded well with measured contaminant concentration data. •Displacement ventilation is proposed to solve unpleasant odor problems in wards.•Heat loss and gain from vertical surfaces cause convective airflow that affects DV.•Influence of the convective airflow on indoor environment in DV was investigated.•Results validate zonal model to predict temperature and contaminant concentration.