Modeling of supply airflow from slot line diffuser on ceiling for CFD of thermal environment in perimeter zone

• Published in: Building and environment 2022-04, Vol.213, p.108884, Article 108884
• Main Authors: Sheng, Shaoyu, Yamanaka, Toshio, Kobayashi, Tomohiro, Yuan, Jihui, Katoh, Masahiro
• Format: Article
• Language: English
• Subjects: CFD Simulation; Full-scale experiment; Perimeter zone; Slot line diffuser; Velocity and turbulence statistics measurement
• ISSN: 0360-1323; 1873-684X
• DOI: 10.1016/j.buildenv.2022.108884

The slot line diffuser is widely used in Japan near the perimeter windows because of its blocking effect on convective heat transfer. However, research on this diffuser has mainly focused on the effects of the turbulence model on CFD simulations and longitudinal airflow distribution, while studies on its detailed outlet characteristics in three-dimensional have been limited. In order to obtain and summarize this diffuser's outlet characteristics more accurately, this paper set a slot line diffuser with an adjustable outlet area in free space. The detailed velocity and turbulence statistics distribution on the diffuser's outlet surface were obtained by a hot-wire anemometer, and the diffuser's airflow distribution in the free space was measured by an ultrasonic anemometer. Then the outlet characteristics of this diffuser were summarized using these measured data in order to make a detailed supply airflow model. At the same time, the difference of the airflow of full-size supply and that of half-size supply is characterized. Moreover, a detailed CFD simulation of the diffuser's outlet airflow was performed using the characteristics model to define the boundary conditions. The detailed CFD result with outlet characteristics model were validated by comparing with experimental data. Additionally, the prescribed velocity (P.V.) method and simple boundary simulation were also attempted to reproduce the diffuser's outlet airflow, and compared with the experiment and detailed CFD results. This study clarified this diffuser's outlet characteristics in three-dimensional, and it is considered that the outlet characteristics model can help improve the simulation accuracy of the kind of diffuser. •Outlet airflow's characteristics under both thermal and isothermal conditions of the slot line diffuser are examined by a full-scale experiment.•Turbulence statistics on the diffuser's outlet surface are calculated based on the X-type probe hotwire anemometer's measurement data.•Outlet characteristics model for slot line diffuser was proposed based on the full-scale experiment. The model can be used to define the boundary data in CFD simulation.•A detailed CFD simulation of the diffuser's outlet airflow was carried out and validated its accuracy.•Detailed CFD simulation result was compared with the CFD simulations using the P.V. method and the simple outlet boundary.