Effect of Outdoor Temperature on Performance of All-air Wall Induction Unit in a Four-bed Hospital Ward

Abstract

The prototype all-air wall induction unit (IU) has the characteristics of displacement ventilation (DV) and windless air supply, which is considered ideal for hospital ward usage. The outdoor temperature, however, will affect its ventilation and thermal performance. This study conducted a full-scale experiment. IUs are vertically installed in the four corners of the experiment room, which is furnished as a Japanese hospital ward. An outdoor climate simulation chamber (OCSC) is installed on one side of the room to simulate the external window and sill under different outdoor temperature conditions. CO2 is generated from the room’s one point, representing pollutants emitted by a patient. The room’s steady-state temperature and CO2 concentration distribution are analyzed under different outdoor temperatures (in OCSC) and air supply conditions. The IU maintained a comfortable thermal environment under all experimental conditions. In terms of ventilation performance, downward airflow undermines concentration stratification in midwinter. The DV stabilizes when the temperature difference between inside and outside air becomes less than 10 °C while using the double-pane window in winter. Conversely, upward airflow strengthens the DV in the summer. In addition, a sufficient supply rate is recommended to keep concentrations and temperatures above the patients’ breathing zone.