Quality of inhaled air in displacement ventilation systems assisted by personalized ventilation

Abstract

The air quality in spaces conditioned by displacement ventilation (DV) aided with personalized ventilation (PV) is assessed on the basis of the average CO₂ concentration levels. The interaction between the displacement ventilation flow, upward flow of the rising occupant plume, exhalation flow, and personalized airflow is modeled in order to predict the CO₂ transport inside the space and the inhalation zone of occupants to monitor the air quality. The contribution of PV in lowering the CO₂ concentration of the inhaled air is evaluated by computing the personal exposure effectiveness in terms of the CO₂ concentrations in PV air and inhaled air with and without PV.

The developed model was validated by comparing model results of CO₂ concentrations with results obtained from 3D simulations using commercial software and with published experimental data for different PV distances from the occupant, flow rates, and temperatures of PV jets. For DV supply temperature of 18°C (64.4°F) and PV air supply temperature range of 18°C to 22°C (64.4°F to 71.6°F), it was found that PV at flows ranging from 4 L/s to 10 L/s (8.48 cfm to 21.19 cfm) could improve the inhaled air quality up to 20% in the breathing zone.

Acknowledgments

M. Kanaan, PhD, is PhD Student. N. Ghaddar, PhD, Member ASHRAE, is Associate Provost and Endowed Qatar Chair in Energy Studies Professor. K. Ghali, PhD, Associate Member ASHRAE, is Associate Professor.