Computational study of breathing methods for inhalation exposure

Abstract

This research uses an experimentally validated computational fluid dynamics model that includes a personal ventilation system, seated thermal manikin, and floor diffuser to assess the effect of breathing methods on two cases with personal ventilation systems and one without personal ventilation. The personal ventilation systems include a single round jet and a novel low-mixing co-flow nozzle that directs fresh air toward the breathing zone. First, experimental and computational air quality results were compared for the nostril and mouth using the same setup. Then, the effect of breathing on air quality profiles was determined and compared to experimental data. Next, the intake fraction was compared for the three cases when modeling four different breathing methods. The breathing methods include steady-state no breathing, steady-state inhalation, unsteady sinusoidal breathing, and an unsteady realistic profile. Based on the intake fraction, the results show that most breathing methods gave the same results within 2–3% for each case. Using an area average over a nostril is not an adequate breathing simulation method. From this, it is recommended that steady inhalation is used to simulate breathing in computational studies because it does not increase the complexity of the simulation and makes post-processing easier.

Acknowledgment

Although the research described in this article has been funded wholly or in part by the United States Environmental Protection Agency (through grant/cooperative agreement CFDA 66.606, Sponsor Award X-83269001-0 to Syracuse University, Strategically Targeted Research in Intelligent Built Environmental Systems), it has not been subjected to the agency's required peer and policy review; therefore, it does not necessarily reflect the views of the agency, and no official endorsement should be inferred.

Jackie Sue Russo, PhD, Student Member ASHRAE. Ezzat Khalifa, PhD, Fellow ASHRAE.