Effectiveness of intermittent personalized ventilation in protecting occupant from indoor particles

• Published in: Building and environment 2018-01, Vol.128, p.22-32
• Main Authors: Assaad, Douaa Al, Habchi, Carine, Ghali, Kamel, Ghaddar, Nesreen
• Format: Article
• Language: English
• Subjects: Average flow; Breathing; Computational fluid dynamics; Computer applications; Contaminants; Deposition; Direct contamination; Flow rates; Flow velocity; Fluid dynamics; Fluid flow; Hydrodynamics; Indirect contamination; Intermittent ventilation; Mathematical models; Microclimate; Migration; Mixing ventilation; Personalized ventilation; Respiration; Temperature effects; Test chambers; Thermal comfort; Three dimensional models; Ventilation
• ISSN: 0360-1323; 1873-684X
• DOI: 10.1016/j.buildenv.2017.11.027

In this study, the performance of an intermittent periodic personalized ventilation (PV) coupled with mixing ventilation (MV) was investigated with respect to its ability in protecting occupant from contaminants present in the space. To perform this study, a transient 3D computational fluid dynamics (CFD) model was used to assess the velocity, temperature and particle concentration fields in the space. Experiments were performed in a climatic chamber using a thermal manikin in order to validate the CFD model's predictions of the fluid flow and particle distribution in the space at supply MV flow rate of 63 L/s and room temperature of 28 °C and PV average flow rate of 3.5 L/s, supply temperature of 24 °C, and frequencies of 0.3 Hz and 1 Hz. Good agreement was found between the CFD model and experiments. The validated model was used to recommend PV operating parameters which would assure occupant protection from macroclimate contaminants' migration to the breathing zone and microclimate surrounding the occupant, and reduce particles' deposition on the surfaces in occupant proximity. It was found that an average flowrate of 7.5 L/s as well as an operating frequency of 0.86 Hz provided acceptable values of intake fractions in the breathing zone and the surrounding microclimate as well as acceptable values of deposition rates. These conditions provide good thermal comfort levels (0.87: comfortable), and good ventilation effectiveness (77.1%). [Display omitted] •Study of effectiveness of intermittent personal ventilation in preventing direct contamination.•The CFD model was experimentally validated at different PV frequencies using a thermal manikin.•Increasing PV frequency minimized direct contamination and decreased particle deposition.•Increasing PV average flowrate reduced direct contamination but increased particle deposition.•A PV flow of 7.5 L/s and frequency of 0.86 Hz assured good breathable air quality.