Assessing the interaction of air from a jet diffuser on a thermal plume in a room using two-dimensional particle image velocimetry

Abstract

Traditional design of airflow distributions in large spaces does not consider the interference of thermal plumes on jets. In order to quantitatively describe the indoor environment, it is first necessary to quantify how the airflow gets distributed. In this study, a two-dimensional particle image velocimetry (PIV) system for measuring a wide indoor flow field was established. A total of 24 sub-regions (each with a size of 400 mm × 350 mm) were accurately measured in an unmanned room, and the overall cross-sectional flow field was obtained by splicing. Uncertainty analysis proved the rationality of this experimental method. According to the damage extent of the jet structure introduced by the thermal plume, two groups were divided, i.e. Groups A and B. The distribution of velocity fields, trajectories and velocity attenuation of jet centerlines, and velocity magnitude profiles at nozzle and head levels were compared and analyzed in detail. Through this investigation, detailed information of indoor air flow in large spaces can be effectively characterized, which can be useful to help understand the indoor physics and validate CFD models. Practical application: The key to creating a comfortable and healthy indoor thermal environment is the rational design of the airflow distribution. This paper proposes a method for quantitatively describing the airflow distribution in an enclosed space. The equation of the non-dimensional velocity attenuation of jet centerlines is obtained by using advanced technology (PIV), which provides theoretical basis and useful reference for the design of airflow distribution.

Particle image velocimetry investigation on air distribution of surface-source buoyancy plume changing heating intensity and structure size in a thermostatic chamber

“…an air scale model and the jet diffusion under the action of heat source was analysed and evaluated. 7 This paper focused on the air distribution of the surface-source plume and on obtaining the formula coefficients in the surface-source plume theory based on the flow field data. The experimental process needed to ensure that the indoor flow field was stable and undisturbed, so all valves of air supply nozzles, air return and air exhaust were closed.…”

“…Unlike the flow field with supply air and return air, this investigation was in an enclosed space without ventilation, so the tracer particles could achieve good measurement effect over a relatively long period. In this experiment, the fog liquid was followed by the glycerol mixture used in the previous experiment, 7 and the seeding concentration produced by the fog machine could be maintained at a constant level for about 25 min. After the fog was released, there would be 10–15 min waiting for the flow field to stabilize again.…”

“…6 However, the indoor airflow pattern design often ignores effects of heat sources in plants. Different types of local heat sources can generate buoyancy-driven thermal plumes, not only destroying the stable interface by the local air conditioner 7 but also causing the uncontrolled diffusion of the oil mist and particles. 8 Therefore, quantifying air distributions of plumes and accurately predicting plume motion are critical to the design and optimization of airflow patterns.…”