Assessment of transport methodologies for dispersion modelling for Indoor Air Quality analysis

Indoor air pollution is being increasingly considered as a significant factor affecting human health. The recent pandemic-induced lock-downs and the remote – work culture have only increased the time spent indoors by the general population. Computational Fluid Dynamics (CFD) is widely employed in dispersion modelling for Indoor Air Quality (IAQ) analysis. This study seeks to understand the differences between the two common transport models used for contaminant dispersion analysis: the scalar transport model and the multi-species transport model using the Reynolds-Averaged Navier Stokes (RANS) model. The objective of the study is to identify the strengths and limitations of both models and identify the computationally efficient methodology having considerable accuracy in different scenarios. Both approaches are bench-marked with test cases: a generic mixing ventilation case and a case of dense gas mixing in a building. For the generic mixing ventilation study, the results generated by the scalar transport model shows better agreement with the experimental study with better computational speed. On the contrary, the multi-species model show better agreement with experimental data for the dense gas mixing problem. The probable reasons behind the difference in accuracy are also explored and a general guideline for the selection of appropriate model is also discussed.