Experimental and numerical analysis of CO₂ transport inside a university classroom: effects of turbulent models

Carbon dioxide (CO2) can reduce cognitive abilities at higher concentrations. CO2 can be used as a proxy for gas transport in an indoor environment and as an index to determine Indoor Air Quality (IAQ). In the present work, CO2 transport inside a real university classroom has been analysed experimentally and numerically. The main novelty is related to the experimental characterization of the airflow, boundary conditions for swirl diffusers and CO2 transport occurring in an actual university classroom equipped with a Turbulent Mixing Airflow (TMA) system. The numerical methodology, validated against the experimental measurements performed by the authors, has been used to identify the most suitable turbulence model for both thermo-fluid dynamic and CO2 transport simulations. Three different RANS k-epsilon turbulence models have been compared: the Standard k-epsilon, the RNG k-epsilon and the Realizable k-epsilon. Moreover, the evacuation time and the effects of turbulent diffusivity have been analysed.