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Ventilation Modeling

Ventilation is used in buildings to create thermally comfortable environments with acceptable indoor air quality by regulating indoor air parameters, such as air temperature, relative humidity, air speed, and chemical species concentrations in the air. In order to regulate the indoor air parameters, it is essential to have suitable tools to predict ventilation performance in buildings. Ventilation performance prediction is to provide the information concerning indoor air parameters in a room or a building.

Ventilation Modeling Methodology

Computer-based airflow analysis for design can be divided into two main categories:
Computational Fluid Dynamics (CFD)
and bulk airflow.
CFD results in a point-in-time (PIT) analysis that requires very complex, iterative calculations to achieve a single result.
Bulk airflow analysis is part of some energy modeling software, often calculated as an average airflow and temperature over an entire hour.
CFD allows a high degree of accuracy but limited time frame, whereas bulk airflow is useful for daily or annual analysis but involves less detail than CFD.

Ventilation Modeling Applications

Urban Design: Urban designers use airflow analysis to test and determine the best design strategies such as massing, determining materials of urban spaces, and selection and proper locating of trees to create open and semi-open spaces with proper ventilation rates and thermal comfort levels.

Architectural Design: Architects use airflow analysis to design buildings with sufficient fresh air supply, natural ventilation with proper airflow speed, avoiding high temperature stratifications, and evacuate contaminant which lead to healthy comfortable indoor spaces.

HVAC Airflow Distribution Systems: Mechanical system designers use airflow analysis to test and determine dimensions of air and water channels and size and place the air distributer terminals to provide a good indoor air quality.

Ventilation Simulation Tools

Simulation tools like ANSYS fluent, Open Foam, COMSOL and some other CFD code programs use the first approach and Energyplus and CONTAM are simulation tools that use the second approach in their calculations.

References

[1] “Building Performance Simulation for Design and Operation - Google Books.” https://books.google.com/books?id=l5p079SDVwQC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false (accessed Feb. 21, 2022).
[2] ASHRAE Green Guide Design, Construction, and Operation of Sustainable Buildings, Tom Lawrence, Abdel K. Darwich, Janice K. Means.
[3] Natural Ventilation in Buildings Architectural concepts, consequences and possibilities, Tommy Kleiven.
[4] The Indoor Environment Handbook; How to make buildings healthy and comfortable, Philomena M. Bluyssen.
[5] Dols, W. and Polidoro, B. (2015), CONTAM User Guide and Program Documentation Version 3.2, Technical Note (NIST TN), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://doi.org/10.6028/NIST.TN.1887 (Accessed February 8, 2022)