Numerical comparison of the efficiency of mixing ventilation and impinging jet ventilation for exhaled particle removal in a model intensive care unit

Abstract

Effective infection prevention and control measures are required in the intensive care units of hospitals, as these areas have a high incidence of nosocomial infections. Adopting proper ventilation pattern that is efficient in pollutant removal is important for controlling the spread of infectious diseases. In this study, the computational fluid dynamics (CFD) simulation approach is used to investigate the airflow pattern, fates of respiratory particles, and patients' intake fraction in a four-bed model intensive care unit under three types of ventilation: impinging jet ventilation and two forms of mixing ventilation. The results show that in contrast to mixing ventilation, the airflow trend of impinging jet ventilation is consistent with the thermal plume of the human body. Accordingly, impinging jet ventilation can efficiently remove pollutants at the ceiling level, thereby reducing cross-infection. Our results also show that fine particles are greatly affected by the ventilation pattern, whereas large particles are primarily removed by surface deposition. The maximum intake fraction of susceptible patients under the three types of ventilation are 8.24 × 10−5 (impinging jet ventilation); 4.5 × 10−4 (ceiling air ventilation; a type of mixing ventilation) and 5.3 × 10−4 (side air ventilation; a type of mixing ventilation). Impinging jet ventilation appears to be the most effective ventilation system for removing particles and reducing susceptible patients’ intake fraction under our investigated scenarios, and exhibits great potential as a ventilation method in intensive care units.