Air Change and Transfer Efficiencies within a Cross-Ventilated Room Model Sheltered by Urban-Like Block Arrays using RANS simulations

Abstract

Natural and cross ventilation is recognized as an important measure for introducing outdoor fresh air to indoor without the use of mechanical equipment. Plenty of fruitful studies for elucidating natural and cross ventilation mechanisms have been reported adopting experimental and computational methods. Field and wind tunnel experiments could provide substantial flow information on indoor-outdoor interaction in actual or reduced model conditions. However, these approaches were relatively costly and time-consuming and limited in terms of spatial and temporal resolutions. Computational fluid dynamics approaches are promising complementary technique to these methods. In this study, we performed isothermal CFD simulations for both airflow and concentration fields for cross-ventilation conditions sheltered by surrounding buildings with two different opening conditions. ANSYS/Fluent was utilized to perform CFD using RANS simulation. Heterogeneity of ventilation efficiencies determined by concentration distributions in cross-ventilated room model were quantitatively analyzed using ventilation efficiencies, e.g., age of air. The results showed that the location of the openings had a significant impact on the cross-ventilation rate, creating completely different concentration fields, and ventilation efficiencies indices could quantitatively demonstrate the formation mechanisms of scalar concentration distributions in an indoor space.