MULTIZONE AIRFLOW MODELS Purpose

Multizone airflow models may be used to evaluate these items:

1. Airflows: Determination of airflow rates in buildings, including infiltration, exfiltration, room-to-room airflows in building systems driven by mechanical means, wind pressures acting on the exterior of the building, and buoyancy effects induced by temperature differences between the building and the outside; design of natural and hybrid (combined natural and mechanical) ventilation systems; determination and checks of pressure hierarchies between zones; influence of infiltration on performance of mechanical ventilation systems; interaction between natural and mechanical driving forces in hybrid ventilation systems.

2. Contaminant concentrations: Dispersal of airborne contaminants such as odors, fumes, smoke, VOCs, etc. transported by these airflows and transformed by a variety of processes including chemical and radiochemical transformation, adsorption, desorption to building materials, filtration, and deposition to surfaces; evolution of contaminant concentrations in the individual zones; air quality checks in terms of C02 levels; cross-contamination evaluation of zones; air quality evaluations in relation to perception as well as health. Methods are also applicable to smoke control design.

3. Personal exposure: Predictions of exposure of occupants to airborne contaminants for risk assessment, inhaled doses, or time-integrated concentration values.

Combined thermal and multizone models are needed for problems such as

Thermal comfort analysis in naturally ventilated buildings, determination of

Heat-removal capacity by natural ventilation, design and evaluation of free

Cooling by nighttime ventilation. This is outlined in more detail in Section 11.5.

Posted in INDUSTRIAL VENTILATION DESIGN GUIDEBOOK