Impact of building porosity on exterior convective heat transfer coefficients: An experimental and computational parametric study

Exterior convective heat transfer is vital for connecting a building and its surrounding environment. With an increasing focus on porous buildings for sustainable design, accurately calculating exterior convective heat transfer is critical, and also poses significant challenges. This study used experimental and computational fluid dynamics (CFD) techniques to assess the impact of building porosity on exterior CHTCs. Onsite measurements at an actual porous building were conducted first for validation, which was further extrapolated by linking the actual porous building with idealized porous buildings. Parametric CFD simulations were then performed on hypothetical isolated buildings with ten different idealized geometries (including one fully enclosed building as a baseline and nine porous buildings) and two wind directions (perpendicular and oblique). The resulting exterior CHTCs obtained through CFD simulations were compared with those from exterior CHTC models in EnergyPlus, along with the resulting differences in cooling load. The findings revealed that the maximum difference in exterior CHTCs between CFD simulations and exterior CHTC models in EnergyPlus was nearly threefold, leading to cooling load deviations of up to 19%. From a practical perspective, this study highlights the impact of building porosity on exterior convective heat transfer, underscoring the importance of considering building porosity in building energy simulation for more accurate cooling load prediction.