Numerical investigation and accuracy verification of indoor environment for an impinging jet ventilated room using computational fluid dynamics

Publication date: April 2017
Source:Building and Environment, Volume 115
Author(s): Tomohiro Kobayashi, Kazuki Sugita, Noriko Umemiya, Takashi Kishimoto, Mats Sandberg
The impinging jet ventilation (IJV) system has been proposed as an air distribution strategy to provide a better thermal environment with a medium supply momentum than displacement ventilation (DV) system. However, no simplified prediction method that is practically applicable has been established to date. The ultimate goal of this study is to establish a calculation model to predict the vertical temperature profile in an IJV system. The authors aim to propose a one-dimensional model, where the room is divided into several control volumes. To perform this, the turbulent thermal diffusion between control volumes needs to be well understood. Therefore, a knowledge about the effect of each design factor such as the supply air velocity on the turbulent thermal diffusivity needs to be acquired through a parametric study. Computational Fluid Dynamics (CFD) is effective for this purpose. As a first step, the accuracy of CFD simulations is verified by conducting a full-scale experiment. The velocity profiles inside the impinging jet and the indoor temperatures are measured and compared with the CFD results. It is shown that the shear-stress transport k-ω model has a sufficient accuracy to analyse the target room, and an appropriate grid layout is established as well. The convection-radiation coupling CFD prediction where the external temperature is used as a boundary condition is adopted as the best method for the numerical study in this research. Finally, a parametric study on the supply air velocity is performed based on this setting and its effect on the thermal stratification is presented.