The effect of human breathing on the effectiveness of intermittent personalized ventilation coupled with mixing ventilation

Abstract

The aim of this work is to study the interaction of human breathing and the intermittent personalized ventilation (IPV) jet and investigate its effectiveness in supplying clean breathable air when operating in relaxed background contaminants’ concentration condition. A transient 3-D computational fluid dynamics (CFD) model of a breathing occupant in an office space equipped with an IPV combined with mixed ventilation system was developed. Two breathing modes were considered: nose breathing and mouth breathing. Tracer gas method was used to evaluate the breathable air quality of the IPV user at different IPV operating frequencies. The flow field resulting from interaction of IPV jet and nose breathing was experimentally validated in a climatic chamber equipped using a breathing thermal manikin. The validated CFD model was used to assess the inhaled air quality at different IPV frequencies in both nose and mouth breathing modes, while comparing it to no-breathing case.It was found that maximum ventilation effectiveness εV ranges during inhalation were obtained at an IPV frequency of 0.5 Hz ranging from 36.75% to 86.6% for nose breathing mode, 49.6%–87.3% for mouth breathing mode and 42.42–86.93% when breathing was not considered. The nose breathing mode gave the lowest εV while the mouth breathing mode gave better εV due to the stronger dilution offered by the horizontally exhaled air. The average εV for the nose and mouth breathing were fairly close to the case of no-breathing and provided satisfactory air quality at the BZ.