Impact of multizone model boundary conditions on the CFD prediction of room airflow and contaminant concentrations distribution

Coupling CFD and muitizone models can avoid their respective drawbacks in predicting airflow and contaminant concentrations distribution in buildings. Two kinds of boundary conditions are commonly exchanged between them. The muitizone model can give either pressure or mass flowrate boundary conditions to CFD. This study analyzes in detail the impact of each of the boundary types on the CFD domain, and compares them with a full CFD simulation without coupling. This study shows that in coupling CFD with muitizone, the accuracy of the CFD prediction part depends mainly on the accuracy of the boundary conditions being imposed at their interface. When modeling a very small opening, pressure boundary conditions give slightly more accurate results. For a moderate opening height, both pressure and flow rate boundary conditions show good agreement with the CFD-only simulation. For a large opening, the mass flow rate boundary conditions are better to use.