Correlations for the forced convective heat transfer at a windward building façade with exterior louver blinds. (October 2020)

• Record Type: Journal Article
• Authors: Jiang, Fujian; Yuan, Yanping; Li, Zhengrong; Zhao, Qun; Zhao, Kaiming
• Is Part Of: Solar energy. Volume 209(2020)
• Page Start: 709
• Page End: 723
• Publication Date: 2020-10
• Subjects: Louver blinds -- CFD simulation -- Building energy simulation -- Convective heat transfer coefficient -- Nusselt number; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2020.07.014
• Languages: English
• ISSNs: 0038-092X

Abstract

Highlights: High-resolution simulations are conducted to investigate convective heat exchange. Discussion of louvers' geometric and thermal attributions on Nu is performed. A model is presented to describe the flow between the façade and louvers. Correlations is established to predict the averaged Nu of the façade with louvers. Abstract: 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 façade 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 façade with louver blinds, which are validated with wind-tunnel experiments. The 3D steady Reynolds-averaged Navier-Stokes (RANS) function with Low-Reynolds Number Modelling (LRNM) treatment has been employed for precision improvement. The theoretical simulations are performed for 5 louver angle φ (from 0° to 60°), 3 installing distance W (from 0.025 H to 0.08 H ), 5 slat width B (from 0.02 H to 0.10 H ), 8 temperature difference between the façade and blinds θ (from 1 to 7) and 5 reference wind velocity UH (from 2.56 m·s −1 to 4.27 m·s −1 ). It was found that the convective heat loss at the louver shows a positive correlation with the growth of φ, W and the reduction of B . Meanwhile, the convective heat loss on the façade behind is positive to B, W and negative to φ and θ. Finally, with some conversions of expressions, a group of correlations are established which can predict the surface-averaged Nu of the façade and louver blinds, of which relative errors are less than 13% compared that of simulation data.