Extension of generalized forced convective heat transfer coefficient expressions for isolated buildings taking into account oblique wind directions. (August 2018)

• Record Type: Journal Article
• Authors: Montazeri, H.; Blocken, B.
• Is Part Of: Building and environment. Volume 140(2018)
• Page Start: 194
• Page End: 208
• Publication Date: 2018-08
• Subjects: Convective heat transfer coefficient -- Computational Fluid Dynamics (CFD) -- Building Energy Simulation (BES) -- Building aerodynamics -- Building energy; Buildings -- Environmental engineering -- Periodicals; Building -- Research -- Periodicals; Constructions -- Technique de l'environnement -- Périodiques; Electronic journals; 696
• DOI: 10.1016/j.buildenv.2018.05.027
• Languages: English
• ISSNs: 0360-1323

Abstract

Abstract: The surface-averaged forced Convective Heat Transfer Coefficient (CHTCavg ) at a windward building facade is influenced by the complex interaction between a wide range of parameters. Existing CHTC expressions, however, consider the impact of these parameters either incompletely or not at all. Earlier studies have shown that this shortcoming can lead to significant errors in Building Energy Simulations. In this paper, therefore, the combined impacts of wind speed (U10 ), building height (H) and width (W), and wind direction (θ) on the CHTCavg for the windward facade of buildings are systematically investigated. High-resolution CFD simulations of wind flow and forced convective heat transfer, validated with wind-tunnel measurements, are performed for 64 building geometries (10 m ≤ H and W ≤ 80 m), 8 wind directions (0° ≤ θ ≤ 78.75°) and 4 reference wind speeds (1 m/s ≤ U10 ≤ 4 m/s). The 3D steady RANS equations with the realizable k-ε turbulence model and the low-Re number Wolfshtein model are used. The results show that for a given building geometry and U10, the CHTCavg decreases as θ increases from 0° to 78.75°. The maximum reduction of about 42% occurs for the building with H = 8W = 80 m. In addition, for a given θ and U10, by increasing H, the CHTCavg increases, while increasing W has the opposite impact on the CHTCavg . Finally, a new generalized CHTC expression is presented as a function of U10, H, W and θ, and its accuracy is confirmed by detailed in-sample and out-of-sample evaluations. Graphical abstract: Image 1 Highlights: Extension of generalized CHTC expressions for windward building facades. Taking into account building width, building height, wind speed and wind direction. Accuracy evaluation based on in-sample and out-of-sample data. Suitable for Building Energy Simulation & Building Envelope Heat-Air-Moisture tools.