<p>The transmission of infectious respiratory diseases has been a topic of broad interest for decades. Exhaled contaminants by different human respiratory activities (such as coughing) constitute one of the major sources of infectious particles in indoor environments. The transmission of such airborne diseases is largely influenced by the ventilation in the space, especially localized ventilation near the infection source (i.e. the infected person). One energy-friendly ventilation technique that has been extensively investigated in contaminant transmission is Personalized Ventilation (PV) integrated with total volume ventilation techniques, notably Mixing Ventilation (MV). Such localized ventilation delivers cool clean air directly towards the breathing zone of the user, procuring acceptable levels of thermal comfort and breathable air quality. However, when used by an infected person, it might amplify the transport of the expiratory droplets and their dispersion into the space, increasing the risk of airborne cross-infection. More recently, PV applications varied the supplied cool clean air intermittently, mimicking natural outdoor conditions in order to enhance occupants’ thermal comfort and improve energy performance. Such system operation is referred to as Intermitted PV (IPV). Nonetheless, the effect of such highly turbulent oscillatory jet on airborne disease dispersion has not been assessed in the literature to the authors’ knowledge.</p><p>In this work, the impact of integrating IPV with MV on cross-contamination is investigated for the case where an infected user is coughing. The IPV is considered to operate at an average flowrate of 10 l/s, with a minimum of 4 l/s at a typical frequency of 0.94 Hz. The infected person is considered seated in a tandem (i.e. back-to-face) position with respect to a healthy person, located at a distance of 1.5 m and not using PV. This reflects the worst-case scenario where the healthy person is not protected by PV. The contamination source is the coughing of the infected person, which lasts for 0.5 s at a speed of 10 m/s. A validated computational fluid dynamics (CFD) model of an office space equipped with IPV+MV is used to assess the cross-contamination between the occupants. A comparison between IPV and steady PV (SPV) of constant flowrate of 10 l/s is conducted to highlight the influence of IPV on contaminants dispersion in the space and the resulting exposure level of a healthy occupant.</p>

Effect of Intermittent Personalized Ventilation on Coughed Particles Dispersion in an Office Space and Resulting Cross Contamination

Paper Proceedings: https://asmedigitalcollection.asme.org/HT/HT2021/volume/84874

ASME 2021 Heat Transfer Summer Conference (SHTC2021)

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