Review of natural ventilation models

Natural ventilation (NV) is an important and efficient passive technique toreduce building cooling energy need and improve indoor air quality. NVdesign requires profound knowledge and accurate prediction of air flowand heat transfer in and around buildings that are highly dependent onvarying external and internal conditions, as well as the building geometryand local site conditions. This paper reviews the important NV models andsimulation tools and the comparisons of their prediction capabilities. A review of the analytical models reveals that these models are generallyonly applicable to specific geometries and driving forces. The complexinteractions between combined driving forces and complex geometriesresults in sets of non-linear equations which must be solved numerically.Prevalent network airflow models are identified and compared, whichgenerally use the same theory, and yield similar, often nearly identicalresults in inter-model comparison studies. Airflow network modelsincorporated into whole building energy simulation tools are alsoassessed.Results have shown that the current airflow model can be usedto model most NV mechanisms, with an exception of wind-driven singlesidedventilation. For the predictable cases, the most accuracy is achievedfor cases with small and simple openings. For larger openings andespecially complicated openings, the model’s predictions are lessaccurate. Furthermore, the model is heavily dependent on severalsomewhat ambiguous coefficients including: wind profile exponent,pressure coefficient, and discharge coefficient