Effect of supply velocity and heat generation density on cooling and ventilation effectiveness in room with impinging jet ventilation system. (November 2021)

• Record Type: Journal Article
• Authors: Yamasawa, Haruna; Kobayashi, Tomohiro; Yamanaka, Toshio; Choi, Narae; Cehlin, Mathias; Ameen, Arman
• Is Part Of: Building and environment. Volume 205(2021)
• Publication Date: 2021-11
• Subjects: Impinging jet ventilation -- Quasi-displacement ventilation -- CFD analysis -- Ventilation effectiveness -- Parametric study -- Archimedes number; air change efficiency (ACE) -- computational fluid dynamics (CFD) -- contaminant removal effectiveness (CRE) -- draught rate (DR) -- displacement ventilation (DV) -- impinging jet ventilation (IJV) -- mixing ventilation (MV) -- particle image velocimetry (PIV) -- Renormalization Group k-ε model (RNG) -- Standard k-ε model (SKE) -- Menter Shear Stress Transport k-ω model (SST); Buildings -- Environmental engineering -- Periodicals; Building -- Research -- Periodicals; Constructions -- Technique de l'environnement -- Périodiques; Electronic journals; 696
• DOI: 10.1016/j.buildenv.2021.108299
• Languages: English
• ISSNs: 0360-1323

Abstract

Abstract: This study aims to understand the effect of supply momentum and heat generation density on the cooling and ventilation effectiveness in a room with an impinging jet ventilation system (IJV). A parametric study was conducted by CFD analysis, and the number of supply terminals and occupants were varied as parameters. CFD validation was conducted before the parametric study by comparing the experimental and analytical results. RNG k-ε and SST k-ω model showed almost the same accuracy for simulating, and SST k-ω model was chosen to be used for the parametric study. It is shown that the larger number of terminals and/or occupants leads to the air distribution to be displacement flow, whereas the smaller number leads to that of mixed condition. The ventilation effectiveness and cooling effectiveness within the room could be kept higher by locating the supply terminal at the centre of the walls than at the corner of the room. When the supply velocity was smaller than 0.833 m/s, the draught rate (DR) at ankle level in the central cross-section could keep lower than: 20% in the region farther than 0.5 m horizontally away from the terminals, and 15% in the region farther than 1.0 m away from the terminals. Finally, the cooling and ventilation effectiveness is expressed as the function of Archimedes number (the balance between supply momentum and buoyancy) in the specific studied cases. The asymptotic values for both large and small Archimedes numbers are obtained for each index expressing cooling and ventilation effectiveness. Highlights: SST k-ω model was adopted for the parametric study. The large number of supply terminals and occupants leads to the displacement flow. The small number of supply terminals and occupants leads to the mixed condition. The draught rate was kept in the acceptable range when supply velocity was small. The ventilation effectiveness was shown as the function of Archimedes number.