The propagation characteristics and assessment of airborne droplets in a general ward
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Abstract:
A good air distribution of a general air-conditioned ward can quickly exclude droplet contaminations generated by indoor patients, which can reduce the infection risk of medical staff and escorts. Based on literature analysis, the authors got basic data such as the particle size, number, speed and temperature of droplets generated by human respiratory activities, and established the physical model of the general ward and the droplet evaporative diffusion model by Fluent. Then, with using the open interface UDF (user-defined function) in Fluent, a UDF program was wrote as the speed input condition to describe the non-state speed distribution of patients’ breathing and coughing droplets, and the propagation characteristics of droplet contaminations in a general ward under three typical airflow forms, i.e. up supply and up return airflow, wall-attached jet airflow and up supply and down return airflow, were simulated. According to the simulation results, droplets with the particle size of 0.1-3 μm have the largest concentration in the respiratory area of both patients and healthy personnel under the three airflow forms. The droplet concentration under up supply and down return airflow in the respiratory area of health personnel is lower than 40% of that under up supply and up return airflow, and lower than about 70% of that under wall-attached jet airflow. The ventilation efficiency under up supply and down return airflow is higher and its effect of excluding droplet contaminations is better, too. It is recommended that up supply and down return airflow should be used in a general ward to reduce the risk of indoor personnel’s cross-infection.
