Review of natural ventilation models

Journal article, 2016

Natural ventilation (NV) is an important and efficient passive technique to
reduce building cooling energy need and improve indoor air quality. NV
design requires profound knowledge and accurate prediction of air flow
and heat transfer in and around buildings that are highly dependent on
varying external and internal conditions, as well as the building geometry
and local site conditions. This paper reviews the important NV models and
simulation tools and the comparisons of their prediction capabilities.
A review of the analytical models reveals that these models are generally
only applicable to specific geometries and driving forces. The complex
interactions between combined driving forces and complex geometries
results in sets of non-linear equations which must be solved numerically.
Prevalent network airflow models are identified and compared, which
generally use the same theory, and yield similar, often nearly identical
results in inter-model comparison studies. Airflow network models
incorporated into whole building energy simulation tools are also
assessed.
Results have shown that the current airflow model can be used
to model most NV mechanisms, with an exception of wind-driven singlesided
ventilation. For the predictable cases, the most accuracy is achieved
for cases with small and simple openings. For larger openings and
especially complicated openings, the model’s predictions are less
accurate. Furthermore, the model is heavily dependent on several
somewhat ambiguous coefficients including: wind profile exponent,
pressure coefficient, and discharge coefficient.