Review of natural ventilation models

Abstract

ABSTRACTNatural 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 single-sided 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.