Multizone models are widely used in building airflow and energy performance simulations because they are often suitable for the analysis needed, and due to their fast computation speed. However, the results provided by the multizone models are sometimes limited due to the underlying well-mixed assumption of the air in a zone (e.g., a room). For zones where this assumption is not suitable, a Computational Fluid Dynamics (CFD) models may be needed. This paper proposes a coupled simulation model between the multizone and CFD model, which in the paper is fast fluid dynamics, a freely available and publicly released program. The model allows the simulation of a dynamic interaction between airflow and Heating, Ventilation and Air-Conditioning (HVAC) systems for buildings with stratified airflow distribution in some of the zones. The approach is implemented using Modelica and its buildings library. In this presentation, we first discuss the design and implementation of a data synchronization strategy between the two models. We then show a possible validation of the implementation by comparing the simulated results with experimental data from previous research. Finally, we perform a case study by linking a Variable Air Volume (VAV) terminal box to space in order to evaluate the capability of the coupled simulation. Finally, further research needs are discussed at the end of the paper.
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