Numerical analysis of Particle Exposure Mitigation in Cooking Activities Through a Residential Ceiling Hood

In the last two decades a significant increase of the scientific interest to airborne particles has been evidenced. Research on this topic enormously accelerated starting from the introduction of standard for Ultra Fine Particles (UFPs) (PM2.5, particles smaller than 2.5 μm) in the USA in 1997, since a better correlation between health effects and fine particles exposure was found (Morawska 2010). Looking at the scientific literature, it is by now evident that both short-term and long term exposure to ambient particulate is associated to mortality and morbidity. In this context UFPs are of particular concern. In fact, they are able to travel to the smaller airways, until alveoli and many of their physical, chemical and microbiological characteristics may cause negative health effects. The particle dimension represents just one such characteristics. Still today it is not clear to what extend health effects are directly related to UFPs emitted for instance by combustion processes (primary particles) or to those formed by complex chemical reactions in the atmosphere (secondary particles). Even tough major particulate sources are related to outdoor activities, most people spend more than 80% of their time indoors (Chen, Yu et al. 2006; Chen and Zhao 2011). As a consequence, assessing indoor particle is very important in order to investigate its impact on human health. Even though both indoor and outdoor sources contribute to concentration and composition of particles in indoor air, more information is usually available about emission characteristic of outdoor particle sources than of indoor ones. Cooking represents one of the most significant indoor particle generating activities. Even thought a number of studies measured the particle number concentration and size distribution generated during cooking activities, more attention should be paid to the effects of the ventilation system on personal exposure. In fact, the operation of an efficient air ventilation system can significantly reduce the exposure and thus, the possible negative health effects. In this work, the efficiency of a ceiling hood in reducing human exposure to UFPs during a cooking activity is numerically investigated by employing a three-dimensional non commercial finite-element code based on the fully explicit Artificial-Compressibility Characteristic Based Split algorithm (AC-CBS) (Arpino, Buonanno et al. 2011). Such a numerical tool was developed by the authors in the recent period and applied to the analysis of three-dimensional heat and mass transfer processes in presence of very large source terms (such as high buoyancy forces). The obtained results have been validated against experiments in term of temperature distributions in correspondence of the hot surface, showing a very good agreement.