Prediction of thermal and contaminant environment in a room with impinging jet ventilation system by zonal model. (1st August 2022)

• Record Type: Journal Article
• Authors: Yamasawa, Haruna; Kobayashi, Tomohiro; Yamanaka, Toshio; Choi, Narae; Cehlin, Mathias; Ameen, Arman
• Is Part Of: Building and environment. Volume 221(2022)
• Publication Date: 2022-08-01
• Subjects: Impinging jet ventilation -- Displacement flow -- Zonal model -- Archimedes number -- Turbulent jet -- Draught risk; CFD computational fluid dynamics -- DV displacement ventilation -- IJV impinging jet ventilation -- SST k-ω Shear Stress Transport k-ω model -- RMSE root-mean-square-error; Buildings -- Environmental engineering -- Periodicals; Building -- Research -- Periodicals; Constructions -- Technique de l'environnement -- Périodiques; Electronic journals; 696
• DOI: 10.1016/j.buildenv.2022.109298
• Languages: English
• ISSNs: 0360-1323

Abstract

Abstract: The impinging jet ventilation (IJV) system has been proposed as a new air distribution strategy and is expected to overcome the disadvantages of the mixing ventilation (MV) system, which is the most widely used system, and displacement ventilation (DV), which provides better air quality than MV. This study aims to predict the vertical profile of temperature and contaminant in a room with impinging jet ventilation system (IJV) by a calculation model based on the zonal model and turbulence jet theory. The correlation between the thickness of the jet along the floor and radial coordinate is obtained by the results of CFD analysis under isothermal conditions and adapted to the model as the height of the first zone from the floor. The concept and theory of the calculation model are introduced, and the calculation results are compared to that of CFD analysis. The turbulent diffusion coefficient in the vertical direction is identified by the CFD results, whereas the turbulent diffusion coefficient in the horizontal direction is obtained by the function of the occupant density in the present paper. Finally, the turbulent diffusion coefficient of vertical direction is expressed as the function of the Archimedes number (balance between buoyancy and inertial force of supply flow) defined in the present paper. It was shown that although some limitations exist, the calculation model developed in the present paper can predict the temperature and contaminant gradient in the room. In addition, the draught risk around the floor is also predicted. Highlights: Zonal model to predict profiles of temperature and contaminant was developed. Height of the first zone was determined based on turbulent jet theory. Vertical temperature profiles were predicted well by present model. Prediction accuracy of contaminant profiles were not as high as temperature. Turbulent thermal diffusivity was shown as the function of Archimedes number.