CFD assessment of intake fraction in the indoor environment

Abstract

In this paper we use a validated CFD model to calculate the inhalation exposure, expressed as an intake fraction (iF), of a seated person in an office with different contaminant sources, a floor diffuser, and a ceiling vent. These sources include the floor, the walls, a desk, and the human body. First, experimental data is used to determine the correct turbulent Schmidt number for the computational model to predict the transport of the species in an indoor environment. It was found at a turbulent Schmidt number of ∼0.9 produced the best fit when compared to experimental data. Then, the iF was calculated for two representations of the computer simulated person (CSP): a CSP with detailed surface geometry, and a simplified CSP with multi-block geometry. It was found that the simplified multi-block geometry is not adequate for predicting iF because it radically changes the flowfield of the thermal plume in the breathing zone (BZ). Next, the effect of personal ventilation systems on iF was investigated. The results show that such systems can reduce the iF by an order of magnitude compared with conventional mixing and displacement ventilation systems. Finally, a comparison of iF results were made for a surface body temperature of 32 °C and 28 °C. It was found that a 4 °C change in body surface temperature influenced the iF by less than 10%.