particle

This study describes the development of a three dimensional (3D) Lagrangian code of particle transport in indoor turbulent flows. This approach consists of integrating transport equations for each particle at each time step to determine successive positions of the particle. The first challenge was to calculate instantaneous velocities of the airflow. The mean component of these velocities was calculated by a classic CFD code. A stochastic process based on the Gosman and Ioannides method generated the fluctuating component. Corrections were applied to better fit experimental results.

This paper presents the investigation results on a simulation program, which calculates the particle trajectory under different airflow patterns in the multi-zones structure building. The numerical simulation is first used to predict airflow pattern and ventilation performance. Then, the particle movement is determined by employing Lagrangian method. The simulation identifies the characteristics of ventilation and indoor air quality.

The demand for duct cleaning has been increasing exponentially over the last few years and to determine objectively if the duct is dirty and has to be cleaned is necessary.All air-handling units from a school district (18 buildings) and representative portions of their associated ductwork were assessed. Results of dirt and contamination are compared to dirt criterias and commented.

Indoor aerosol particulate matter (PM) concentrations were measured gravimetrically in 36 carpeted bedrooms of asthmatic children. Particulate concentration was higher indoors than outdoors. High efficiency particule arresting (HEPA) filtration was shown dividing concentrations by about 2.

The filtration efficiency of residential furnaces air filters was measured in several houses in Canada. Even efficient filters have a minor influence on particulate levels in houses. The ways to reduce these levels were investigated. Results show for example how HEPA filters on supply air reduce indoor particle concentration.

Maintenance is often limited to repair and failure response and not dedicated to indoor environment. The study defines levels of cleanliness depending on the method of measurement and compares surface values on the components to air pollution in order to decide if guidelines with limit values for surfaces are sufficient.

Ways of removing from indoor air particulates smaller in diameter than 1 micrometer, through enhancement of particle deposition in a filter, were investigated using numerical simulation. Deposition enhancement is obtained using diamond-shaped three-dimensional roughness elements incorporated into filters. Numerical investigations performed were used to define the enhancement for laminar flow, in order to define the most efficient arrangement of enhancing elements.

Measurements were carried out in a test chamber with displacement ventilation to know the vertical distribution of airborne particles generated by two human subjects having an activity representative of that of people working in an office. Particle concentration was observed as increasing with height. A threshold size of particles was found at 5 to 10 microns above which the displacement effect of particles by air flow started to decline. Negative concentration gradients were observed for large particles at the lowest ventilation rate, when the air flow does not displace them.

Particles distribution in type and size were determined in six office buildings in Oslo (Norway).

Two aluminium windows were tested to determine the fractional penetration of airborne particles. Results show that mainly particles of 0.2 to 3 microns enter through both windows.