Performance of all-air wall induction unit for displacement ventilation in a four-bed hospital ward during the cooling period

Abstract

The existing induction air-conditioning system faces ventilation shortcomings and condensation risks. We developed an all-air wall induction air terminal unit (wall IU) that doesn't require reheating and eliminates water pipes to address condensation. Moreover, with modifications to its supply method, it can achieve displacement ventilation (DV) in an adiabatic environment. However, the real-world performance of this system needs to be further confirmed. This study examines wall IU performance during the cooling period. A full-scale experiment was conducted in a room furnished as a four-bed hospital ward with an outdoor climate chamber (OCC) to simulate summer conditions. IU's cooling and ventilation performance was evaluated by examining steady-state temperatures and tracer gas distributions. Moreover, CFD simulations to reproduce the experiment were performed to supplement the results. Patients' thermal comfort and infection risk while cohabiting with an infected individual were estimated using detailed temperature, airflow, and concentration data from an experiment-based CFD analysis. Furthermore, the DV stratification height under various perimeter heat loads and performance comparison between wall and ceiling-mounted induction units were also studied. In conclusion, the wall IU improved ventilation efficiency by achieving DV under cooling supply conditions. Satisfied thermal comfort is ensured based on ADPI and DR evaluation. DV's stratification height can be kept high enough under a 20 °C equivalent temperature difference when using a single glass window or more after thermal insulation enhancement. Compared with ceiling-mounted induction units, wall-mounted units can reduce infection risk by more than double while making cold drafts less noticeable.