IJV12

The aim of this study was to develop a simplified CFD model for the inlet jet of a swirl diffuser for the simulation of room airflow patterns. The swirl diffuser creates a complex flow pattern with high induction of room air, thus possessing a challenge for simulation. The studied diffuser was a model intended to be used in large enclosures. The flow pattern was adjustable between two basic modes: radial swirl jet for cooling conditions and compact downward swirl jet for heating conditions. For developing the CFD model, a series of laboratory measurements of the flow field was carried out.

Industrial buildings, as in the nuclear industry, are equipped with ventilation systems, the main role of which is to ensure pollutant containment inside the facility during normal, damaged or accidental situations. To do this, the ventilation system is designed to maintain rooms at lower pressure with respect to the outside environment. The air, taken from the outside, thus flows from the rooms with the lowest contamination risk to the rooms with the highest contamination risk, before being filtered and released into the atmosphere.

A pilot survey was undertaken from September 2009 to June 2011 in 310 schools and day-care centres distributed in all regions of France including overseas departments. This experimental survey was carried out as part of the preparation of the mandatory control of indoor air quality in public buildings. Three parameters were measured in 896 classrooms or child playrooms: benzene, formaldehyde and carbon dioxide (CO2). The last enables the determination of degree of air ‘stuffiness’ during children occupancy as well as the night-time air change rate.

A quadrature method of moments, based on the population balance approach, was chosen to model nanoparticle coagulation and transport. Such a way has been already validated using experimental results in a homogeneous closed chamber in a steady fluid. In order to model the spatiotemporal evolution of a nano-aerosol, we propose here to couple the population balance equation (PBE) with computational fluid dynamics (CFD) considering a uniform pipe flow. A source term describing coagulation is added in convection-diffusion equations.

The use of supply jet flows is the most common type of air distribution for general ventilation. Usually the supply flow rate is constant or slowly varying (VAV-systems) to cope with a varying load. A novel air distribution method, with the potential to reduce stagnation and to increase the ventilation efficiency, is to introduce rapid flow variations (pulsations). This paper reports on a fundamental study of this type of air distribution.