Natural ventilation of an isolated generic building with a windward window and different windexchangers: CFD validation, sensitivity study and performance analysis

Windexchangers are relatively small structures located on the building rooftop to promote natural ventilation. This paper presents a Computational Fluid Dynamics (CFD) validation study, sensitivity analysis and performance comparison of three windexchanger (WE) configurations applied to a generic isolated building with a windward window. The study is limited to wind-driven (isothermal) ventilation, for wind perpendicular to the windward facade. The CFD simulations are based on the 3D-steady Reynolds-Averaged Navier-Stokes (RANS) equations. The validation study is performed with experimental results from a previously published water channel test. The sensitivity analysis focuses on the domain size, grid resolution and turbulence model. The performance evaluation of the three WE configurations is based on the mean velocity and mean static pressure coefficients in the vertical centerplane, the ventilation volume flow rate and the volume percentage of the living zone with air speed ratio equal to or above 0.10. The WE configuration with four openings and one duct shows the highest ventilation flow rate (0.232 m(3)/s) and the highest volume percentage (21%). This study shows that the assessment and selection of WE configurations should not only be based on volume flow rate or ACH but should consider the living zone air speed ratio as well, specifically concerning the flow distribution in the living zone.