Correlations for the forced convective heat transfer at a windward building facade with exterior louver blinds

Exterior louver blinds are increasingly utilized to protect the building envelope from solar radiation. However, with the existing correlations from studies on a smooth flat/a surface of the bluff body, the convective heat exchange at louver blinds and the facade behind them will be underestimated and overestimated respectively. In this work, Computational Fluid Dynamic (CFD) simulations have been conducted to analyze the forced convective heat transfer at the windward facade with louver blinds, which are validated with wind-tunnel experiments. The 3D steady Reynolds-averaged Navier-Stokes (BANS) function with Low-Reynolds Number Modelling (LRNM) treatment has been employed for precision improvement. The theoretical simulations are performed for 5 louver angle phi (from 0 degrees to 60 degrees), 3 installing distance W (from 0.025H to 0.0811), 5 slat width B (from 0.02H to 0.1011), 8 temperature difference between the facade and blinds theta (from 1 to 7) and 5 reference wind velocity U-H (from 2.56 m.s(-1) to 4.27 ms(-1)). It was found that the convective heat loss at the louver shows a positive correlation with the growth of phi, W and the reduction of B. Meanwhile, the convective heat loss on the facade behind is positive to B, W and negative to phi and theta. Finally, with some conversions of expressions, a group of correlations are established which can predict the surface-averaged Nu of the facade and louver blinds, of which relative errors are less than 13% compared that of simulation data.